Tag Archives: LinuxKernel

June Linux Patch Wednesday

Leave a reply

June Linux Patch Wednesday

June Linux Patch Wednesday. A total of 1,888 vulnerabilities (324 in the Linux kernel, and a whopping 728 in Chromium ❗️). For comparison, there were 1,638 vulnerabilities in May. The increase isn't as dramatic as it was from April to May, but it's still a new record. One of the vulnerabilities has been flagged as actively exploited in the wild:

🔻 RCE - Chromium (CVE-2026-11645). Chromium is the open-source web browser project that serves as the foundation for many modern browsers, including Google Chrome, Microsoft Edge, Brave, Opera, and Vivaldi. A publicly available Metasploit module exploits a vulnerability in the web browser's V8 JavaScript engine. The vulnerability is triggered by a specific code pattern that causes type confusion between internal V8 objects, resulting in out-of-bounds memory access. Successful exploitation may lead to remote code execution in the context of the browser process.

There are also 109 vulnerabilities with public exploits or evidence that exploits exist, although there are no signs of active exploitation in real-world attacks yet. Among them, the following stand out:

🔸 EoP - Linux Kernel "CIFSwitch" (CVE-2026-46243). This vulnerability could allow attackers to forge CIFS authentication key descriptions, abuse the kernel's key request mechanism, and gain root privileges.

🔸 EoP - Linux Kernel "PinTheft" (CVE-2026-43494). On a successfully exploited configuration, the chain completes and hands off to the discovered SUID binary with an overwritten first page - yielding a root shell if the race and kernel state align.

🔸 RCE - Apache ActiveMQ (CVE-2026-42588). ActiveMQ is an open-source message broker written in Java. Exploitation of this vulnerability requires valid credentials for the ActiveMQ Web Console. However, the default credentials are admin/admin.

🔸 InfDisc - Squid "Squidbleed" (CVE-2026-47729). Squid is an open-source caching proxy server. The vulnerability causes Squid's FTP parser to read beyond the boundary of a memory buffer, into a region that may contain a previous user's uncleared HTTP request data.

🔸 AuthBypass - Nextcloud (CVE-2026-45156). Nextcloud is an open source content collaboration platform. A missing signature verification in User OIDC allowed a malicious ID4me authority to identify as any user.

🔸 XSS - Nextcloud (CVE-2025-59788). A vulnerability in a reachable files_pdfviewer example directory in Nextcloud allows attackers to execute arbitrary JavaScript in the context of a user's browser via a crafted PDF file to viewer.html.

🔸 XSS - Roundcube (CVE-2026-48849). Roundcube is a free, open-source webmail application. An unsanitized subject field in the draft restored value could lead to stored XSS/HTML/CSS injection on shared mailboxes.

🔸 DoS - ImageMagick (CVE-2026-46522). ImageMagick is an open-source image processing tool used to create, edit, and convert images. Due to a missing check in the MIFF decoder, a crafted file could cause an infinite loop resulting in CPU exhaustion.

🗒 Full Vulristics report

June "In the Trend of VM" (#28): Linux kernel, Microsoft Defender, and Palo Alto Networks device vulnerabilities

Leave a reply

June In the Trend of VM (#28): Linux kernel, Microsoft Defender, and Palo Alto Networks device vulnerabilities

June "In the Trend of VM" (#28): Linux kernel, Microsoft Defender, and Palo Alto Networks device vulnerabilities. Presenting the traditional monthly roundup of trending vulnerabilities according to Positive Technologies. In the previous May edition, we covered four vulnerabilities. This time, there are also four vulnerabilities associated with five CVE identifiers.

🗞 Post on Habr (rus)
🗒 Digest on the PT website (rus)

🔻 EoP - Linux Kernel "Dirty Frag" (CVE-2026-43284, CVE-2026-43500). A chain of vulnerabilities with a public exploit to obtain root access. There are signs of in-the-wild exploitation.

🔻 EoP - Linux Kernel "Fragnesia" (CVE-2026-46300). Another vulnerability for gaining root access with a public exploit.

🔻 EoP - Microsoft Defender "RedSun" (CVE-2026-41091). A privilege escalation vulnerability leading to SYSTEM-level access, with a public exploit available and indications of in-the-wild exploitation. Pay special attention to Windows server and desktop environments where Microsoft Defender is enabled but there is no Internet access for regular updates.

🔻 RCE - PAN-OS (CVE-2026-0300). An unauthenticated RCE with root privileges affecting PA-Series and VM-Series firewalls. A public exploit exists, and there are indications of in-the-wild exploitation.

🟥 The full list of trending vulnerabilities is available on the portal

May Linux Patch Wednesday

Leave a reply

May Linux Patch Wednesday

May Linux Patch Wednesday. A total of 1,638 vulnerabilities (474 in the Linux kernel). For comparison, in April there were 1,035 vulnerabilities (a record!). And this time it turns out to be a record again, more than one and a half times higher! The acceleration is both impressive and alarming. But we will see what happens next. At some point it should stabilize. Although the number of critical vulnerabilities is already so high that reviewing all of them becomes quite problematic. For 7 vulnerabilities there are signs of exploitation in the wild. And for another 264 there are public exploits. Let’s start, as usual, with vulnerabilities being actively exploited according to CISA KEV and VulnCheck KEV data. Here, at the top, as expected, are two high-profile ways to get a root shell:

🔻 EoP - Linux Kernel "Copy Fail" (CVE-2026-31431)
🔻 EoP - Linux Kernel "Dirty Frag" (CVE-2026-43500)

Other vulnerabilities being exploited in the wild:

🔻 RCE - Apache ActiveMQ (CVE-2026-40466). Based on the description, this appears to be a bypass of the fix for CVE-2026-34197, which I already wrote about earlier.

🔻 AuthBypass - Rclone (CVE-2026-41176). Rclone ("rsync for cloud storage") is a command-line utility for synchronizing files and directories between various cloud storage services and local systems. Exploitation of the vulnerability can lead to unauthorized access to sensitive administrative functionality, including configuration and operational RC methods.

🔻 RCE - NGINX (CVE-2026-42945). The bug enables unauthenticated remote code execution against servers using rewrite and set directives.

🔻 DoS - PgBouncer (CVE-2026-6664). PgBouncer is a lightweight, open-source connection pooler for PostgreSQL databases. It reduces connection overhead by managing a pool of connections to one or more PostgreSQL servers, improving performance and resource efficiency for applications with frequent short-lived database connections. An integer overflow in the network packet parsing code in PgBouncer before 1.25.2 bypasses a boundary check and can lead to a crash.

🔻 XSS - Postorius (CVE-2026-44742). The Postorius Django app provides a web user interface to access GNU Mailman. Mailman is free software for managing electronic mail discussion and e-newsletter lists. The vulnerability is being exploited according to VulnCheck KEV; however, no public exploits has been observed yet.

From the remaining vulnerabilities with public exploits, but without any signs of exploitation in the wild so far, the following can be highlighted:

🔸 RCE - Apache HTTP Server (CVE-2026-23918). Double-free error in Apache httpd mod_http2 stream cleanup, leading to pre-auth RCE.

🔸 RCE - Apache Tomcat (CVE-2026-34486). Apache Tomcat Tribes cluster communication module fails to discard messages when EncryptInterceptor decryption fails, allowing unauthenticated attackers to trigger Remote Code Execution via Java deserialization on port 4000.

🔸 RCE - ProFTPD (CVE-2026-42167). The flaw exists in how mod_sql handles certain logging variables (like %U), allowing an unauthenticated attacker to inject SQL commands via the USER command.

🔸 EoP - Linux Kernel "DirtyDecrypt" (CVE-2026-31635). Linux local privilege escalation in the RxRPC/GSSAPI decryption path. A missing skb_cow_data() check in rxgk_decrypt_skb() allows an unprivileged local attacker to corrupt cache pages and overwrite in-memory contents of read-only files.

🔸 EoP - Linux Kernel "Fragnesia" (CVE-2026-46300). I also analyzed this vulnerability earlier. A bug in skb_try_coalesce() allowing page-cache write via fragmented ESP packets.

🔸 EoP - Linux Kernel (CVE-2026-46333). Local root privilege escalation and credential disclosure in the Linux kernel ptrace path, discovered by researchers at Qualys.

🔸 EoP - PackageKit "Pack2TheRoot" (CVE-2026-41651). PackageKit is a free and open-source suite of software applications designed to provide a consistent and high-level abstraction layer for a number of different package management systems. The vulnerability allows an attacker to escalate privileges, potentially gaining root access or compromising the system.

🔸 ComInj - Composer (CVE-2026-40261, CVE-2026-40176). Composer is a dependency manager for PHP. The vulnerability exists in the Perforce::generateP4Command() method. Due to insufficient sanitization of repository configuration parameters (such as url, p4user, or client) when constructing shell commands, an attacker who controls a composer.json file can execute arbitrary commands on the victim's system when composer install or composer update is executed.

🗒 Full Vulristics report

About Elevation of Privilege - Linux Kernel "Fragnesia" (CVE-2026-46300) vulnerability

Leave a reply

About Elevation of Privilege - Linux Kernel Fragnesia (CVE-2026-46300) vulnerability

About Elevation of Privilege - Linux Kernel "Fragnesia" (CVE-2026-46300) vulnerability. The vulnerability was discovered by researcher William Bowling together with the V12 team. Fragnesia belongs to the class of Dirty Frag vulnerabilities. It is an error in the ESP/XFRM subsystem, distinct from Dirty Frag, which was addressed with a separate patch. It allows achieving arbitrary byte writes into the kernel page cache of read-only files, without requiring any race condition.

🛠 Technical details and exploit code were published on May 15. The public exploit modifies the contents of /usr/bin/su in the kernel page cache, and then executes /usr/bin/su, resulting in the user obtaining a root shell. The on-disk binary is never modified. A reboot or cache flush restores normal system behavior.

⚙️ Fragnesia affects the same kernel versions as Dirty Frag. Any distribution shipping a kernel without the May 13 patch is vulnerable. The vulnerability was confirmed on Ubuntu 6.8.0-111-generic (April 11, 2026 build). Monitor kernel package updates for your Linux distribution(s).

For systems where a kernel update is not possible, the same workaround as for Dirty Frag is effective (blacklisting modules). Systems where the Dirty Frag workaround has already been applied are already protected against Fragnesia. Systems that only received Dirty Frag updates without applying the workaround remain vulnerable and require new updates addressing Fragnesia.

May "In the Trend of VM" (#27): high-profile vulnerabilities in Linux, ActiveMQ, SharePoint, and Adobe Acrobat Reader

Leave a reply

May In the Trend of VM (#27): high-profile vulnerabilities in Linux, ActiveMQ, SharePoint, and Adobe Acrobat Reader

May "In the Trend of VM" (#27): high-profile vulnerabilities in Linux, ActiveMQ, SharePoint, and Adobe Acrobat Reader. Presenting the traditional monthly roundup of trending vulnerabilities according to Positive Technologies. While the previous April edition featured only one vulnerability, this one includes four, covering different technologies and attack scenarios.

🗞 Post on Habr (rus)
🗒 Digest on the PT website (rus)

🔻 EoP - Linux Kernel "Copy Fail" (CVE-2026-31431). The vulnerability allows an attacker to gain root privileges.

🔻 RCE - Apache ActiveMQ (CVE-2026-34197). A vulnerability in a solution widely used in enterprise systems and integration platforms.

🔻 Spoofing - Microsoft SharePoint Server (CVE-2026-32201). A vulnerability in a Microsoft solution widely used in enterprise systems for collaboration, document management, and internal portal development.

🔻 RCE - Adobe Reader (CVE-2026-34621). A vulnerability in a widely used PDF document viewer; actively exploited in phishing attacks.

🟥 The full list of trending vulnerabilities is available on the portal

About Elevation of Privilege vulnerability - Linux Kernel "Dirty Frag" (CVE-2026-43284, CVE-2026-43500) vulnerability

Leave a reply

About Elevation of Privilege vulnerability - Linux Kernel Dirty Frag (CVE-2026-43284, CVE-2026-43500) vulnerability

About Elevation of Privilege vulnerability - Linux Kernel "Dirty Frag" (CVE-2026-43284, CVE-2026-43500) vulnerability. According to information from researcher Hyunwoo Kim (@v4bel), Dirty Frag is a vulnerability (a class of vulnerabilities) that allows a local unprivileged attacker to obtain root privileges on most Linux distributions by combining the xfrm-ESP Page-Cache Write vulnerability (CVE-2026-43284) and the RxRPC Page-Cache Write vulnerability (CVE-2026-43500). Exploitation of this chain enables the attacker to fully compromise the system: gain access to any files, disable protections, establish persistence, and use the host for further attacks.

⚙️🛠 The vulnerability chain description, technical write-up and exploit code were published on May 7. Exploitability has been confirmed on up-to-date distributions including Ubuntu 24.04.4, RHEL 10.1, openSUSE Tumbleweed, CentOS Stream 10, AlmaLinux 10, and Fedora 44. The xfrm-ESP Page-Cache Write vulnerability has been present in the kernel since commit cac2661c53f3 (2017-01-17) and up to the current upstream version, while the RxRPC Page-Cache Write vulnerability has been present in the kernel since commit 2dc334f1a63a (2023-06) and up to the current upstream version. In other words, the actual time span during which these vulnerabilities have existed in the kernel is around 9 years.

Information about the vulnerability and the exploit was published before patches were available in affected Linux distributions. According to the researcher, on May 7 he submitted detailed information about the vulnerability and the exploit to the linux-distros mailing list. The embargo was set for 5 days, with an agreement that if a third party published the exploit on the internet during the embargo period, the "Dirty Frag" exploit would be released publicly. On the same day, this is exactly what happened: the information was leaked to the public, and the embargo was violated. 🤷‍♂️ As a result, the researcher proceeded with full disclosure.

A similar high-profile vulnerability, Elevation of Privilege - Linux Kernel "Copy Fail" (CVE-2026-31431), served as the motivation for this research. As the researcher reports, the xfrm-ESP Page-Cache Write vulnerability in the Dirty Frag chain shares the same sink as Copy Fail. However, it is triggered regardless of whether the algif_aead module is available. In other words, even on systems where the publicly known Copy Fail mitigation (algif_aead blacklist) is applied, Linux remains vulnerable to Dirty Frag.

Why is a chain of two vulnerabilities used? As the researcher reports, the xfrm-ESP Page-Cache Write vulnerability provides a powerful arbitrary 4-byte STORE primitive, similar to Copy Fail, and is present in most distributions. However, its exploitation requires the privilege to create a namespace. In Ubuntu, unprivileged user namespace creation is sometimes restricted by AppArmor policy. In such an environment, xfrm-ESP Page-Cache Write cannot be triggered. The RxRPC Page-Cache Write vulnerability does not require the privilege to create a namespace, but the rxrpc.ko module itself is not included in most distributions. However, on Ubuntu, the rxrpc.ko module is loaded by default. Chaining the two variants makes the blind spots cover each other, allowing root privileges to be obtained on every major distribution.

As of May 8, the fix for the xfrm-ESP Page-Cache Write (CVE-2026-43284) vulnerability has been merged into the mainline Linux kernel, while the fix for the RxRPC Page-Cache Write (CVE-2026-43500) vulnerability has not yet been merged. It is recommended to monitor the release of security updates for CVE-2026-43284 and CVE-2026-43500 across the Linux distributions in use and apply them promptly. As a workaround, the vulnerability researcher proposes a script that prevents loading of the esp4, esp6, and rxrpc modules, attempts to unload them from the kernel, and clears the Linux memory cache:

sh -c "printf 'install esp4 /bin/false\ninstall esp6 /bin/false\ninstall rxrpc /bin/false\n' > /etc/modprobe.d/dirtyfrag.conf; rmmod esp4 esp6 rxrpc 2>/dev/null; echo 3 > /proc/sys/vm/drop_caches; true"

👾 On May 11, the vulnerability chain was added to VulnCheck KEV, indicating that it has been exploited in the wild.

About Elevation of Privilege - Linux Kernel "Copy Fail" (CVE-2026-31431) vulnerability

Leave a reply

About Elevation of Privilege - Linux Kernel Copy Fail (CVE-2026-31431) vulnerability

About Elevation of Privilege - Linux Kernel "Copy Fail" (CVE-2026-31431) vulnerability. A local privilege escalation vulnerability in the Linux kernel AF_ALG component, which is caused by a memory handling flaw, allows an unprivileged user to escalate privileges to root. By exploiting this vulnerability, an attacker can fully compromise the system: read and modify any files, including passwords and keys, replace system binaries, disable security controls and monitoring tools, stealthily install backdoors and maintain persistence, hide traces of their activity, and use the host as a foothold for attacks on other network assets.

⚙️🛠 On April 1, patches addressing the vulnerability were merged into the main branch of the Linux kernel. On April 22, a CVE identifier was assigned to the vulnerability. On April 29, experts from Theori published an analysis of the vulnerability and a public exploit. The vulnerability's exploitability has been confirmed on up-to-date versions of widely used Linux distributions, including Ubuntu, Amazon Linux, RHEL, and SUSE.

👾 On May 1, the vulnerability was added to the CISA KEV catalog, indicating it is being exploited in the wild.

What distinguishes this vulnerability from similar EOP/LPE issues in Linux?

There have been high-profile privilege escalation vulnerabilities in the Linux kernel. Dirty COW required winning a race condition. Multiple attempts were often needed, and this sometimes led to system crashes. Dirty Pipe was tied to specific versions and required precise pipe buffer manipulation.

But unlike Dirty COW and Dirty Pipe, researchers report that Copy Fail is a straight-line logic flaw. It triggers without races, retries, or crash-prone timing windows.

🧬 Portability. The same exploit script works across all tested distributions and architectures, including Ubuntu, Amazon Linux, Red Hat Enterprise Linux (RHEL), and SUSE Linux Enterprise. No per-distribution offsets. No recompilation. No version checks in the exploit.

✧ Minimalism. The entire exploit is a short Python script using only standard library modules (os, socket, zlib). It requires Python 3.10+ for os.splice. No compiled payloads, no dependency installation.

🥷 Stealth. The write bypasses the ordinary VFS write path. The corrupted page is never marked dirty by the kernel's writeback machinery. Standard file integrity tools that compare on-disk checksums will not detect it, because the on-disk file remains unchanged. Only the in-memory page cache is corrupted.

📦 Cross-container impact. The page cache is shared across all processes on the system, including across container boundaries. Copy Fail is not just a local privilege escalation. It is a container escape primitive and a vector for Kubernetes node compromise.

How to fix the vulnerability?

To remediate the vulnerability, users need to update to Linux kernel versions 6.18.22, 6.19.12, and 7.0. The kernel can be built manually, or users can wait for their Linux distribution vendor to release updated kernel packages. As of May 4, updates have been released for Ubuntu, Debian, RHEL, Fedora, SUSE, CloudLinux, Arch Linux, and ROSA Linux.

As a workaround, researchers suggest blocking the creation of AF_ALG sockets:

echo "install algif_aead /bin/false" > /etc/modprobe.d/disable-algif-aead.conf
rmmod algif_aead 2>/dev/null