From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-80836][MODERATE 7.0] crypto: virtio - bound the akcipher result length Date: Fri, 04 Sep 2026 14:29:29 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-80836 X-AL-KERNEL-Priority: MODERATE 7.0 X-AL-KERNEL-Severity: MODERATE 7.0 X-AL-KERNEL-Base-Severity: MODERATE X-AL-KERNEL-KPANIC: YES X-AL-KERNEL-ActionableScore: 6 X-AL-KERNEL-ActionableScore-Lower: 5 X-AL-KERNEL-Commit: 5545de5050cbc3594506d74f2c392b0716cf8bca List-Id: CVE: CVE-2026-80836 Priority: MODERATE 7.0 AL-KERNEL base severity: MODERATE KPANIC flag: YES Patch: crypto: virtio - bound the akcipher result length Commit: 5545de5050cbc3594506d74f2c392b0716cf8bca Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=5545de5050cbc3594506d74f2c392b0716cf8bca Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80836 Analysis date: Fri, 04 Sep 2026 14:29:29 -0400 ActionableScore: 6 ActionableScore lower bound: 5 Actionable bucket: Actionable Moderate / Strong Important candidate requiring manual review Manual review required: YES Summary: No one-sentence report phrase was found. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-80836 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80836 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 7.0 Manual review required: YES A detailed explanation of the methodology and priority rules is included at the end of this message. ====================================================================== AL-KERNEL CLASSIFICATION RESULT ====================================================================== CVE-2026-80836 MODERATE https://www.kernelcve.org/list/?q=CVE-2026-80836 CHECK WITH IMPACT FROM ORIG NN MODERATE Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:L';CWE-125;CWE-126;*CWE-200;*CWE-20;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:N/A:N';BEST CVSS score: '7.1';DESCR 'A kernel heap out of bounds read in the virtio crypto akcipher callback occurs because the result length reported by the virtio crypto backend is assigned to akcipher_req dst_len without being bounded by the originally allocated destination buffer size. A malicious or non conforming backend can report a larger result length, causing sg_copy_from_buffer to read past vc_akcipher_req dst_buf and copy adjacent kernel heap bytes into the callers scatterlist. For the CVSS the PR:N is used in the paranoid virtualization threat model because a malicious virtio backend or device does not need privileges inside the guest OS, while the base local requester model can be treated as PR:L when a guest user must initiate the crypto request. The issue is not Internet network reachable and is specific to systems using virtio crypto with akcipher operations. Impact is primarily confidentiality loss through kernel heap information disclosure, with possible limited availability impact if the over read faults or destabilizes the guest kernel.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate / Strong Important candidate requiring manual review (with actual score 6) SKIP CVE-2026-80836 UNKNOWN SKIP The Fixes patch not applied yet, so unlikely that actual: url YES NO NO unknown MAYBE OOB VIRT SIMPLEFIX HARDWARE LINUS KPANIC KPANIC INCREASED_TO_HIGH_BASED_ON_ACTIONABLESCOREHIGHERTHAN5 DECREASED_TO_MODERATE7_BASED_ON_FALSEPOSCHECKOFKP - - checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=6 ActionableScoreLower=5 PrimitiveClass=CLASS_A RealUAF=NO HostAdminRequired=UNKNOWN NamespaceScopedPrivilege=NO ImportantCandidate=YES ManualReview=REQUIRED AutoDowngradeAllowed=NO 1. ActionableScore * Raw conservative score: 5 * Conservative score: 5. No floor or cap applied. * Raw paranoid score: 6 * Paranoid score: 6. No floor or cap applied. * Final recommended bucket: **Actionable Moderate / Strong Important candidate requiring manual review**:: 2. Signal breakdown Conservative signals: * +2: Strong disclosure primitive. The patch directly establishes an out-of-bounds kernel heap read because a device-reported akcipher result length is used as the copy length without being bounded to the originally allocated destination buffer. * +1: Confidentiality plausible. The over-read bytes are copied by sg_copy_from_buffer() from the kernel heap buffer into the caller scatterlist, giving a concrete disclosure path. * +1: Firmware/device-mediated external influence. The malicious or non-conforming virtio crypto backend controls the reported response length. * +1: Practical exploit chain. The vulnerable length flows directly into the copy size and the copied data reaches the caller output buffer. Paranoid additional signal: * +1: In common configurations with a guest-accessible crypto requester path, such as a userspace crypto API or a guest service using akcipher, the requester may be able to observe the leaked output. This is not used as a conservative signal because the exact caller path is not shown in the patch. Non-awarded signals: * +0: RealUAF not awarded. No lifetime violation or stale object use is shown. * +0: Arbitrary write not awarded. The patch shows an out-of-bounds read, not an overwrite. * +0: Controlled reclaim not demonstrated. * +0: Privilege escalation not demonstrated. * +0: Reliable crash / strong DoS not awarded. A fault from the over-read is possible but not directly established as the primary behavior. * +0: Remote network reachability not awarded. The issue is virtio-backend mediated, not Internet or packet reachable. * +0: Extra availability not awarded. Any availability concern would be from the same over-read and is not independently demonstrated. * +0: Memory layout invariant not separately counted because it is the same length-vs-buffer-size fact already counted as the OOB disclosure primitive. 3. Reachability analysis The direct source of attacker-controlled input is the virtio crypto backend or device, which reports a result length larger than the original destination buffer. This is not a normal remote network attacker model. It is a virtualization or device-mediated model. The complete practical scenario likely involves either a malicious or compromised backend, or a non-conforming device, plus a guest-side caller that submits an akcipher request and can observe the returned scatterlist data. The patch does not prove that an ordinary unprivileged local guest user can always reach the full path, so HostAdminRequired is UNKNOWN rather than NO. It also does not prove that host-admin-equivalent privilege is always required, because device-backed or delegated backend models may vary. NamespaceScopedPrivilege is NO because no namespace-scoped capability path is involved. Prior setup requires a system using virtio crypto with akcipher support. No race is involved. No special physical-only hardware requirement is established, but the vulnerable path is feature-specific to virtio crypto. 4. Primitive and severity interpretation The exact primitive is a kernel heap out-of-bounds read from vc_akcipher_req->dst_buf caused by trusting the backend-reported result length. The stale/lifetime rules do not apply because this is not a UAF. This is a fixed buffer over-read with a concrete disclosure sink into the caller scatterlist. It is not a write primitive and does not by itself establish memory corruption, credential modification, callback control, or privilege escalation. The demonstrated consequence is kernel heap information disclosure. A limited availability effect is possible if the over-read faults, but this is secondary and not the main established primitive. PrimitiveClass is CLASS_A because the patch establishes a concrete kernel heap disclosure path, not merely an internal invalid read. ImportantCandidate is YES because kernel heap disclosure from a device-controlled length can be security-relevant and should not be automatically downgraded. AutoDowngradeAllowed is NO because a concrete confidentiality primitive would be lost by automatic closure. Likely operational severity is Actionable Moderate at minimum, with Strong Important review justified depending on whether the affected deployment exposes virtio crypto akcipher operations to an attacker-observable guest caller. 5. One-sentence report phrase A virtio crypto backend can report an oversized akcipher result length, causing sg_copy_from_buffer() to over-read adjacent guest kernel heap memory into the caller scatterlist and potentially disclose sensitive kernel data. 6. Manual review recommendation MANUAL CHECK REQUIRED Reason: the patch establishes a concrete kernel heap OOB read with a plausible disclosure path, and deployment-specific review is needed to determine who can control the backend response and who can observe the caller scatterlist output. 7. Call-site confidence Call-site confidence: medium ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: crypto: virtio - bound the akcipher result length Commit: 5545de5050cbc3594506d74f2c392b0716cf8bca Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=5545de5050cbc3594506d74f2c392b0716cf8bca Commit description: virtio_crypto_dataq_akcipher_callback() sets the result length from the device-reported response length without bounding it to the destination buffer, which was allocated for the original request length. sg_copy_from_buffer() then reads that many bytes from the destination buffer; a backend reporting a larger length over-reads adjacent kernel heap into the caller's scatterlist (an out-of-bounds read). Clamp the reported length to the originally requested destination length. A conforming device reports no more than that, so valid results are unaffected. Fixes: a36bd0a ("virtio-crypto: adjust dst_len at ops callback") Cc: stable@vger.kernel.org Signed-off-by: Bryam Vargas Message-ID: <20260622-b4-disp-3a2c09a8-v2-1-d1a809281db4@proton.me> Signed-off-by: Michael S. Tsirkin Signed-off-by: Greg Kroah-Hartman Changed files: drivers/crypto/virtio/virtio_crypto_akcipher_algs.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=5545de5050cbc3594506d74f2c392b0716cf8bca ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-80836 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80836 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: AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:N/A:N The Best / paranoid CVSS vector: AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:L The Best / paranoid CVSS score: 7.1 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: 5 Paranoid ActionableScore: 6 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: YES Published priority for this report (same as in Subject): MODERATE 7.0 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).