From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-46033][IMPORTANT] crypto: authencesn - reject short ahash digests during instance creation Date: Wed, 27 May 2026 15:59:43 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-46033 X-AL-KERNEL-Priority: IMPORTANT X-AL-KERNEL-Severity: IMPORTANT X-AL-KERNEL-Base-Severity: IMPORTANT X-AL-KERNEL-KPANIC: YES X-AL-KERNEL-ActionableScore: 8 X-AL-KERNEL-ActionableScore-Lower: 6 X-AL-KERNEL-Commit: b69933e97efea238ebbfcf70c2b1be1cd03f13e3 List-Id: CVE: CVE-2026-46033 Priority: IMPORTANT AL-KERNEL base severity: IMPORTANT KPANIC flag: YES Patch: crypto: authencesn - reject short ahash digests during instance creation Commit: b69933e97efea238ebbfcf70c2b1be1cd03f13e3 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=b69933e97efea238ebbfcf70c2b1be1cd03f13e3 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46033 Analysis date: Wed, 27 May 2026 15:59:43 -0400 ActionableScore: 8 ActionableScore lower bound: 6 Actionable bucket: Strong Important candidate / Actionable Moderate at minimum Manual review required: YES Summary: No one-sentence report phrase was found. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-46033 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46033 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: IMPORTANT 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-2026-46033 IMPORTANT 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:H/I:H/A:H';*CWE-787;CWE-125;*CWE-20;CWE-754;Other CVSS 'AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:H';BEST CVSS score: '7.8';DESCR 'authencesn can inherit an invalid default authsize when the selected ahash has a digest size from 1 to 3 bytes. AF_ALG can then exercise the ESN encrypt or decrypt path with a too short tag, while that path still moves 4 bytes of high order sequence number data at the end of the authenticated data, causing an out of bounds access. For the CVSS the PR:L is used because a local user with access to AF_ALG can select the affected crypto construction and trigger the operation without full administrator privileges. The issue is not network reachable by itself. Impact is at least local denial of service via kernel memory access fault, with confidentiality and integrity impact retained in the paranoid score because the bug is an out of bounds access in a user controlled crypto data path.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Strong Important candidate / Actionable Moderate at minimum (with actual score 8) MAYBE OOB INIT LINUS KPANIC KPANIC INCREASED_TO_HIGH_BASED_ON_GUESSCVSS - - checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=8 ActionableScoreLower=6 1. ActionableScore * Conservative score: 6 * Paranoid score: 8 * Final recommended bucket: **Strong Important candidate / Actionable Moderate at minimum**:: 2. Signal breakdown * Local unprivileged trigger: +1. A local user with AF_ALG access can instantiate the affected authencesn construction and exercise the AEAD operation. * Local unprivileged high-control kernel data-plane API: +1. AF_ALG gives user space fine-grained control over crypto algorithm selection, buffers, tags, and operation parameters. * Generic memory corruption / OOB access: +2. The commit explicitly states that too-short authsize can make the ESN path hit an out-of-bounds access. * Reliable kernel crash / strong DoS: +1. An OOB access in the crypto data path can plausibly fault or crash the kernel. * Availability impact realistic: +1. Local DoS is the minimum realistic impact. * Paranoid confidentiality impact: +1. OOB access in a user-controlled crypto path may expose adjacent kernel data depending on direction and buffer layout. * Paranoid integrity impact: +1. The ESN path moves 4 bytes at the authenticated-data tail, so a too-short tag may create an OOB write or corruption concern, although a controlled overwrite primitive is not proven. 3. Reachability analysis The issue is local, not network reachable by itself. A user needs access to AF_ALG and to the affected crypto template combination such as authencesn with an ahash digest size of 1..3 bytes. This does not normally require full administrator privileges on systems exposing AF_ALG to unprivileged users. Containers may matter if AF_ALG sockets are available inside the container, because the vulnerable code still executes in the host kernel. 4. Severity interpretation This is more serious than ordinary Moderate because it is an OOB access reachable through a high-control local kernel API. The realistic demonstrated impact is local kernel crash or memory access fault. The paranoid interpretation is Strong Important candidate because user-controlled crypto buffer handling plus OOB access may plausibly affect confidentiality or integrity, even though the patch does not prove arbitrary write or a full LPE chain. 5. One-sentence report phrase A local AF_ALG user can create an authencesn instance with an invalid short default authsize and trigger ESN tail handling with a too-short tag, causing an out-of-bounds kernel access and possible DoS or memory corruption. 6. Manual review recommendation MANUAL CHECK REQUIRED. This is a local high-control AF_ALG path with explicit OOB access, so it should not be auto-closed even without a demonstrated privilege escalation exploit. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: crypto: authencesn - reject short ahash digests during instance creation Commit: b69933e97efea238ebbfcf70c2b1be1cd03f13e3 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=b69933e97efea238ebbfcf70c2b1be1cd03f13e3 Commit description: authencesn requires either a zero authsize or an authsize of at least 4 bytes because the ESN encrypt/decrypt paths always move 4 bytes of high-order sequence number data at the end of the authenticated data. While crypto_authenc_esn_setauthsize() already rejects explicit non-zero authsizes in the range 1..3, crypto_authenc_esn_create() still copied auth->digestsize into inst->alg.maxauthsize without validating it. The AEAD core then initialized the tfm's default authsize from that value. As a result, selecting an ahash with digest size 1..3, such as cbcmac(cipher_null), exposed authencesn instances whose default authsize was invalid even though setauthsize() would have rejected the same value. AF_ALG could then trigger the ESN tail handling with a too-short tag and hit an out-of-bounds access. Reject authencesn instances whose ahash digest size is in the invalid non-zero range 1..3 so that no tfm can inherit an unsupported default authsize. Fixes: f15f05b ("crypto: ccm - switch to separate cbcmac driver") Cc: stable@kernel.org Reported-by: Yifan Wu Reported-by: Juefei Pu Co-developed-by: Yuan Tan Signed-off-by: Yuan Tan Suggested-by: Xin Liu Tested-by: Yuhang Zheng Reviewed-by: Eric Biggers Signed-off-by: Yucheng Lu Signed-off-by: Ren Wei Signed-off-by: Herbert Xu Signed-off-by: Greg Kroah-Hartman Changed files: crypto/authencesn.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=b69933e97efea238ebbfcf70c2b1be1cd03f13e3 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-46033 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-46033 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:L/PR:L/UI:N/S:U/C:L/I:L/A:H The Best / paranoid CVSS vector: AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H The Best / paranoid CVSS score: 7.8 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: 6 Paranoid ActionableScore: 8 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: IMPORTANT KPANIC detected for this report: YES Published priority for this report (same as in Subject): IMPORTANT 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).