From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-64004][MODERATE REGULAR] net/iucv: fix locking in .getsockopt [ Upstream Date: Sun, 19 Jul 2026 19:35:19 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-64004 X-AL-KERNEL-Priority: MODERATE REGULAR X-AL-KERNEL-Severity: MODERATE REGULAR X-AL-KERNEL-Base-Severity: MODERATE X-AL-KERNEL-KPANIC: NO X-AL-KERNEL-ActionableScore: 2 X-AL-KERNEL-ActionableScore-Lower: 1 X-AL-KERNEL-Commit: 884eb247b74d86db97e3a37f0d6fc8e1e83590dd List-Id: CVE: CVE-2026-64004 Priority: MODERATE REGULAR AL-KERNEL base severity: MODERATE KPANIC flag: NO Patch: net/iucv: fix locking in .getsockopt [ Upstream Commit: 884eb247b74d86db97e3a37f0d6fc8e1e83590dd Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=884eb247b74d86db97e3a37f0d6fc8e1e83590dd Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64004 Analysis date: Sun, 19 Jul 2026 19:35:19 -0400 ActionableScore: 2 ActionableScore lower bound: 1 Actionable bucket: Ordinary Moderate / Low-like Manual review required: NO Summary: A local AF_IUCV HIPER socket user can race `recvmsg()` with `getsockopt(SO_MSGSIZE)` so that `iucv->hs_dev` is set to NULL before it is dereferenced, causing a kernel NULL pointer dereference and local denial of service. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-64004 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64004 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: MODERATE REGULAR 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-2026-64004 MODERATE CHECK WITH IMPACT FROM ORIG NN LOW Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H';CWE-362;CWE-667;**CWE-476;BEST CVSS score: '4.7';DESCR 'A race in AF_IUCV HIPER socket handling can allow getsockopt(SO_MSGSIZE) to dereference iucv hs_dev after a concurrent recvmsg close path has set it to NULL. This produces a NULL pointer dereference and kernel oops, resulting in local denial of service. For the CVSS the PR:L because a local user or local process must be able to use an AF_IUCV HIPER socket and race recvmsg with getsockopt on the affected socket. The issue is not directly network reachable because the trigger is a local socket API race rather than packet processing from a remote peer. Impact is denial of service only based on the available patch context, with no supported evidence of information disclosure, arbitrary write, UAF exploitation, or privilege escalation.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like (with actual score 2) YES LOCK DANGER NULLPTR SIMPLEFIX INCREASED_FROM_LOW_BASED_ON_REQUIREMANUALCHECK DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5 NO NO checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=2 ActionableScoreLower=1 ## 1. ActionableScore * Conservative score: 1 * Paranoid score: 2 * Final recommended bucket: **Ordinary Moderate / Low-like** ## 2. Signal breakdown Conservative signals: * Local unprivileged trigger: +1. Any local AF_IUCV HIPER user may race `recvmsg()` with `getsockopt(SO_MSGSIZE)`. * Reliable kernel crash / strong DoS: +1. The described failure is a NULL pointer dereference oops in kernel context. * Hard or unreliable race / special timing required: -1. The trigger depends on winning a race between socket close handling and `getsockopt()`. * Rare AND difficult-to-reach subsystem/configuration: -1. AF_IUCV HIPER is s390-specific and not a broad default Linux networking path. Paranoid interpretation: * Uses +1 local trigger and +1 crash. * Does not subtract the rarity/timing penalties as strongly, because the commit says any AF_IUCV HIPER user can potentially crash the kernel. * No memory corruption, UAF, LPE, confidentiality, or integrity signals are awarded. No generic memory corruption signal applies. The patch and commit describe a NULL pointer dereference after `hs_dev` is set to NULL, not stale freed-object reuse, UAF reclaim, overwrite, type confusion, callback control, or refcount abuse. ## 3. Reachability analysis The bug is locally triggerable by a process that can create and use an AF_IUCV HIPER socket and call `recvmsg()` and `getsockopt(SO_MSGSIZE)` concurrently on the affected socket. It is not directly network reachable, because the trigger is a local socket API race rather than packet parsing from a remote peer. Namespaces do not obviously make this broadly reachable. The affected subsystem is architecture and configuration specific, mainly relevant to s390 IUCV/HIPER environments. There is no evidence that ordinary remote traffic can trigger the bug without a local process using the socket API. Call-site confidence: high. The patch directly changes `iucv_sock_getsockopt()` and the commit explicitly identifies the racing `recvmsg()` path and the NULL dereference target. ## 4. Severity interpretation This behaves like an ordinary Moderate / Low-like kernel DoS issue, not an Important-class vulnerability. The theoretical impact is a kernel crash through a race-triggered NULL pointer dereference. The realistic exploitation evidence supports local denial of service only. There is no supported privilege escalation path. The patch does not show UAF reuse, attacker-controlled reclaim, write-after-free, arbitrary write, type confusion, callback dispatch, information disclosure, or sensitive-object access. Therefore the issue should not be elevated to Actionable Moderate or Important based on the provided evidence. ## 5. One-sentence report phrase A local AF_IUCV HIPER socket user can race `recvmsg()` with `getsockopt(SO_MSGSIZE)` so that `iucv->hs_dev` is set to NULL before it is dereferenced, causing a kernel NULL pointer dereference and local denial of service. ## 6. Manual review recommendation MANUAL CHECK RECOMMENDED This is recommended only because it is a kernel race in a socket subsystem. However, the currently supported primitive is a NULL pointer dereference DoS only, so it does not require urgent Important-class handling. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: net/iucv: fix locking in .getsockopt [ Upstream Commit: 884eb247b74d86db97e3a37f0d6fc8e1e83590dd Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=884eb247b74d86db97e3a37f0d6fc8e1e83590dd Changed files: net/iucv/af_iucv.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=884eb247b74d86db97e3a37f0d6fc8e1e83590dd ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-64004 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64004 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:H/PR:L/UI:N/S:U/C:N/I:N/A:H The Best / paranoid CVSS score: 4.7 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: 1 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: MODERATE KPANIC detected for this report: NO Published priority for this report (same as in Subject): MODERATE REGULAR 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).