From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-52928][LOW] af_unix: Reject SIOCATMARK on non-stream sockets Date: Wed, 24 Jun 2026 04:23:46 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-52928 X-AL-KERNEL-Priority: LOW X-AL-KERNEL-Severity: LOW X-AL-KERNEL-Base-Severity: LOW X-AL-KERNEL-KPANIC: NO X-AL-KERNEL-ActionableScore: 2 X-AL-KERNEL-ActionableScore-Lower: unknown X-AL-KERNEL-Commit: 645b1ed3259af38b7814242a420bc2081bdd1eb6 List-Id: CVE: CVE-2026-52928 Priority: LOW AL-KERNEL base severity: LOW KPANIC flag: NO Patch: af_unix: Reject SIOCATMARK on non-stream sockets Commit: 645b1ed3259af38b7814242a420bc2081bdd1eb6 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=645b1ed3259af38b7814242a420bc2081bdd1eb6 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-52928 Analysis date: Wed, 24 Jun 2026 04:23:46 -0400 ActionableScore: 2 ActionableScore lower bound: unknown Actionable bucket: Ordinary Moderate / Low-like Manual review required: NO Summary: AF_UNIX SIOCATMARK incorrectly accepted non-stream sockets even though MSG_OOB is only supported for SOCK_STREAM, but the patch indicates an API validation fix with no demonstrated confidentiality, integrity, availability, or privilege escalation impact. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-52928 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-52928 The original announcement does not normally provide a security severity estimate, CVSS assessment, or enough information to determine whether the reported kernel bug represents a practically relevant security issue. This report was generated by AL-KERNEL, an AI-assisted Linux kernel vulnerability analysis system developed by Alexander Larkin. It combines an autonomous classifier with LLM-assisted technical analysis and a separate ActionableScore mechanism. The purpose of this report is to prioritize Linux kernel CVEs before manual review, identify cases that require prompt investigation, and support automatic closure of issues that are unlikely to have meaningful security impact. Published priority for this report: LOW Manual review required: NO A detailed explanation of the methodology and priority rules is included at the end of this message. ====================================================================== AL-KERNEL CLASSIFICATION RESULT ====================================================================== CVE-2026-52928 LOW CHECK Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:N';*CWE-20;CWE-754;CWE-703;BEST CVSS score: '0';DESCR 'AF_UNIX SIOCATMARK could be called on SOCK_DGRAM or SOCK_SEQPACKET sockets even though AF_UNIX out of band data is supported only for SOCK_STREAM. This is an API consistency and missing socket type validation issue because non stream sockets already reject MSG_OOB in sendmsg and recvmsg. For the CVSS the PR:L value is used because triggering requires a local process that can create an AF_UNIX socket and call ioctl. The issue is not network reachable. No confidentiality integrity or availability impact is evident from the code path because the ioctl only reports mark state and the patch does not indicate memory corruption, crash, or privilege bypass.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like (with actual score 2) YES REMOTE OOB SIMPLEFIX SKB LOWERED_FROM_HIGH_BASED_ON_GUESSCVSS DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5 DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3 YES NO checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=2 ## 1. ActionableScore * Conservative score: 2 * Paranoid score: 2 * Final recommended bucket: **Ordinary Moderate / Low-like**:: ## 2. Signal breakdown * Local unprivileged trigger: +1. A local process can create an AF_UNIX SOCK_DGRAM or SOCK_SEQPACKET socket and call ioctl SIOCATMARK. * Broad/default/common subsystem: +1. AF_UNIX sockets are a common local IPC mechanism and normally available on Linux systems. * No memory corruption: +0. The patch only rejects an unsupported ioctl use before inspecting the receive queue. * No reliable kernel crash / strong DoS: +0. The commit does not describe panic, Oops, WARN-based crash, stall, UAF, OOB access, or resource exhaustion. * No confidentiality or integrity impact: +0. SIOCATMARK only reports urgent mark state, and MSG_OOB is unsupported for these socket types. ## 3. Reachability analysis The issue is locally reachable by an unprivileged process through AF_UNIX socket creation and ioctl. It is not network reachable because AF_UNIX is local IPC. Namespaces do not materially increase severity, because the operation does not cross a meaningful security boundary and does not expose privileged objects. The path is broadly available, but the observable effect is only that an unsupported operation returned a result instead of EOPNOTSUPP. ## 4. Severity interpretation This behaves like a validation/API consistency issue, not an actionable kernel vulnerability. There is no concrete exploit primitive, no memory lifetime issue, no write primitive, no sensitive disclosure, and no demonstrated DoS. Theoretical concern is minimal because the fixed code only adds a socket type check before receive queue inspection. ## 5. One-sentence report phrase AF_UNIX SIOCATMARK incorrectly accepted non-stream sockets even though MSG_OOB is only supported for SOCK_STREAM, but the patch indicates an API validation fix with no demonstrated confidentiality, integrity, availability, or privilege escalation impact. ## 6. Manual review recommendation NO MANUAL CHECK NEEDED Reason: no memory corruption, no network reachability, no privilege escalation path, no reliable DoS, and no sensitive-object access primitive are supported by the commit or patch. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: af_unix: Reject SIOCATMARK on non-stream sockets Commit: 645b1ed3259af38b7814242a420bc2081bdd1eb6 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=645b1ed3259af38b7814242a420bc2081bdd1eb6 Commit description: SIOCATMARK reports whether the receive queue is at the urgent mark for MSG_OOB. In AF_UNIX, MSG_OOB is supported only for SOCK_STREAM sockets. SOCK_DGRAM and SOCK_SEQPACKET reject MSG_OOB in sendmsg() and recvmsg(), so they should not support SIOCATMARK either. Return -EOPNOTSUPP for non-stream sockets before checking the receive queue. Fixes: 314001f ("af_unix: Add OOB support") Cc: stable@kernel.org Reported-by: Yuan Tan Reported-by: Yifan Wu Reported-by: Juefei Pu Reported-by: Xin Liu Suggested-by: Kuniyuki Iwashima Signed-off-by: Jiexun Wang Signed-off-by: Ren Wei Reviewed-by: Kuniyuki Iwashima Link: https://patch.msgid.link/20260506140825.2987635-1-n05ec@lzu.edu.cn Signed-off-by: Jakub Kicinski Signed-off-by: Greg Kroah-Hartman Changed files: net/unix/af_unix.c Diff excerpt: Not included in this email. See the upstream URL for the full patch. Full patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=645b1ed3259af38b7814242a420bc2081bdd1eb6 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-52928 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-52928 The original CVE announcement normally does not include a security-level estimate. In particular, it may not contain a CVSS assessment, an impact level, or enough information to determine whether the reported bug is a practically relevant security issue. One purpose of this parallel CVE list is to provide that missing technical and prioritization information. The original goal of the AL-KERNEL project was to prioritize Linux kernel CVE analysis automatically before manual review. The system can also help identify non-security issues that may be suitable for automatic closure. This report was generated by AL-KERNEL, an AI-assisted Linux kernel vulnerability analysis system developed by Alexander Larkin. The first analysis stage combines an autonomous classifier with additional LLM-based analysis. The autonomous classifier runs locally on a CPU and is based on a backpropagation neural network. Together, these mechanisms produce a technical vulnerability description, identify likely weakness types, estimate CVSS severity, and provide input for ActionableScore. Two CVSS estimates are retained because incomplete kernel vulnerability information often permits more than one defensible interpretation: Conservative CVSS vector: Not available The Best / paranoid CVSS vector: AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:N The Best / paranoid CVSS score: 0 The conservative vector represents a lower-impact interpretation. The Best/paranoid vector intentionally represents a plausible upper-bound interpretation and should not automatically be treated as demonstrated real-world impact. CVSS may also need to be adjusted for a particular Linux deployment, because actual reachability, privileges, enabled kernel configuration, hardware, namespaces, exposed device nodes, and other environmental conditions can differ significantly between systems. A separate ActionableScore mechanism evaluates practical remediation urgency. Its analysis may include reachability, attack prerequisites, subsystem exposure, memory-corruption characteristics, denial-of-service reliability, and possible confidentiality, integrity, or privilege-escalation impact. Conservative ActionableScore: unknown Paranoid ActionableScore: 2 The final base severity is taken directly from the second tab-separated field of the AL-KERNEL classification result. ActionableScore does not replace or independently override that final AL-KERNEL decision, and if ActionableScore adjusted impact level of ALKERNEL, then you would see self-readable flags above like INCREASED_TO_HIGH_BASED_ON_ACTIONABLESCOREHIGHEREQTHAN7. For an AL-KERNEL result of MODERATE, this report uses the following additional presentation split: ActionableScore below 5 -> MODERATE REGULAR ActionableScore 5 or more -> MODERATE 7.0 The distinction between MODERATE REGULAR and MODERATE 7.0 makes it possible to identify Moderate issues that should receive manual analysis and fixes before lower-priority MODERATE REGULAR issues. In many cases, MODERATE REGULAR fixes may wait for a later rebase or routine update. There is one override in which MODERATE REGULAR becomes MODERATE 7.0 even when the ActionableScore is below 5. When the AL-KERNEL result contains the KPANIC flag, a MODERATE result is always presented as MODERATE 7.0. The KPANIC flag selected with few regexps without usage of AI at all, so it helps to detect cases when Kernel Crash happens and similar (to filter False-Negative results from the LLM usage). KPANIC indicates that a reliable kernel crash, kernel panic, or similarly serious kernel availability impact was identified by the classification workflow. AL-KERNEL base severity for this report: LOW KPANIC detected for this report: NO Published priority for this report (same as in Subject): LOW These results are intended to support engineering triage. They are machine-generated estimates, and cases marked for manual review should be validated by a human security engineer before final disposition. For more info read docs linked from here: https://kernelcve.org/ (and you can submit you own patch there to generate such a report for non-existant CVE-id yet). Note that in many cases this AI tool selects higher severity, than real is (means you can expect Importants instead of Moderate 7.0 or Moderates 7.0 instead of regular Moderates). If you see such cases, please use reply email interface to add additional manual analyses info to this particular CVE. And please, please, let me know when you see Lows instead of Importants or Important instead of Low (because particular for such cases I need to tune this AI tool to make it better for this one and next similar). My contact email for such notifications is alexanjelausa@gmail.com (and both send reply to CVE record itself too and see "reply" button below for howto reply).