From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-80811][LOW] io_uring/cmd: fix iovec leak when the async cmd is not recycled Date: Fri, 04 Sep 2026 13:33:00 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-80811 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: 1 X-AL-KERNEL-Commit: b6a768aa975b9ca81b92f028bdd975d1f8237894 List-Id: CVE: CVE-2026-80811 Priority: LOW AL-KERNEL base severity: LOW KPANIC flag: NO Patch: io_uring/cmd: fix iovec leak when the async cmd is not recycled Commit: b6a768aa975b9ca81b92f028bdd975d1f8237894 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=b6a768aa975b9ca81b92f028bdd975d1f8237894 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80811 Analysis date: Fri, 04 Sep 2026 13:33:00 -0400 ActionableScore: 2 ActionableScore lower bound: 1 Actionable bucket: Ordinary Moderate Manual review required: NO Summary: No one-sentence report phrase was found. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-80811 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80811 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-2026-80811 LOW https://www.kernelcve.org/list/?q=CVE-2026-80811 CHECK WITH IMPACT FROM ORIG NN LOW 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:H';*CWE-401;*CWE-772;**CWE-400;Other CVSS 'AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '5.5';DESCR 'io_uring command requests can leak the cached iovec array stored in io_async_cmd when async command data is dropped without freeing the inherited vec. A practical trigger is an NVMe passthrough workload where queued commands keep async command objects alive and queue depth above the cmd cache limit makes cache put fail. For the CVSS the PR:L is used because a local user or process must be able to submit io_uring uring_cmd requests to an eligible provider such as NVMe passthrough. The issue is not network reachable and requires local execution plus access to the relevant device or command provider. Impact is denial of service via gradual kernel memory exhaustion. No confidentiality or integrity impact is assigned because the bug is a resource leak and does not show a UAF, OOB access, or arbitrary write primitive.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate (with actual score 2) SKIP CVE-2026-80811 UNKNOWN SKIP The Fixes patch not applied yet, so unlikely that actual: url YES NO NO unknown MAYBE KASAN INIT LEAK IO_URING INCREASED_FROM_LOW_BASED_ON_HIGHCVSSSCORE DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN4 DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3 - - checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=2 ActionableScoreLower=1 PrimitiveClass=NONE RealUAF=NO HostAdminRequired=UNKNOWN NamespaceScopedPrivilege=NO ImportantCandidate=NO ManualReview=NO AutoDowngradeAllowed=YES 1. ActionableScore * Raw conservative score: 1 * Conservative score: 1 * Raw paranoid score: 2 * Paranoid score: 2 * No floor or cap changed the score. * Final recommended bucket: **Ordinary Moderate**:: 2. Signal breakdown Conservative positive signals: * +1 Concrete persistent kernel resource leak. The patch directly shows that ac->vec.iovec can be lost when io_alloc_cache_put() fails or when an inherited cached vec is not marked with REQ_F_NEED_CLEANUP. Paranoid additional signals: * +1 Sustained resource exhaustion plausible. The commit describes an ordinary NVMe passthrough workload where live objects track queue depth and cache puts start failing above IO_ALLOC_CACHE_MAX 128, so repeated workload can accumulate leaked kernel memory. Non-awarded signals: * +0 Real UAF not awarded. The bug is a missing io_vec_free() and missing cleanup flag, not stale post-free object use. * +0 Concrete repeated release/refcount not awarded. There is no second put/free/refcount mutation through a potentially dangling reference. * +0 Strong DoS not awarded conservatively. The evidence supports gradual memory leakage, not an immediate or few-operation host-wide crash. * +0 C/I impact not awarded. No information disclosure, arbitrary write, OOB access, UAF, or ownership/security-boundary bypass is established. * +0 Local unprivileged trigger not awarded. Local execution is needed, but complete below-host-admin access to the required uring_cmd provider such as NVMe passthrough is not established. * +0 Remote reachability not awarded. This is not network-triggerable. * No negative privilege penalty was applied because host-admin-equivalent privilege is not positively established. 3. Reachability analysis The vulnerable path is local io_uring uring_cmd use with a command provider that allocates or reuses io_async_cmd vector storage. The commit gives NVMe passthrough as the practical workload, where queued commands can keep async command objects alive and exceed the command cache capacity. The complete privilege boundary is not fully established from the supplied patch. A local process must be able to submit io_uring uring_cmd requests to an eligible device or provider. This may be restricted by device-node permissions or deployment policy, but host-admin-equivalent privilege is not proven. Therefore HostAdminRequired is UNKNOWN. No namespace-scoped capability path is shown. No network trigger is shown. No special rare hardware requirement is scored, because NVMe passthrough is a realistic subsystem path, but access to the relevant device may be permission-gated. There is no race requirement. The issue follows deterministic cleanup and cache-capacity behavior. 4. Primitive and severity interpretation The exact primitive is a persistent kernel memory/resource leak of the iovec array stored in io_async_cmd vec.iovec. It is not memory corruption, not a UAF, not a double free, and not a repeated lifetime/refcount mutation. The demonstrated consequence is gradual kernel memory consumption under repeated or sufficiently deep uring_cmd workloads. The paranoid interpretation allows host availability impact through sustained memory exhaustion, but this remains resource-exhaustion behavior rather than an Important-grade corruption primitive. PrimitiveClass is NONE because no meaningful corruption, stale lifetime use, ownership violation, authorization bypass, or security-boundary primitive is established. ImportantCandidate is NO because the issue is a concrete leak without unresolved memory-corruption or privilege-escalation leverage. AutoDowngradeAllowed is YES because automatic downgrade would not discard a concrete UAF, repeated-release primitive, controlled corruption, or boundary bypass. Likely operational severity is ordinary Moderate or Low-like, depending on whether untrusted local users have access to the relevant uring_cmd provider. 5. One-sentence report phrase io_uring uring_cmd can leak cached iovec arrays when async command data is not recycled or an inherited vec is not marked for cleanup, allowing a local workload such as NVMe passthrough to cause gradual kernel memory exhaustion. 6. Manual review recommendation NO MANUAL CHECK NEEDED Reason: this is a concrete resource leak with possible sustained DoS, but no UAF, repeated refcount mutation, arbitrary read/write, information disclosure, privilege escalation, or security-boundary bypass is established. 7. Call-site confidence Call-site confidence: high ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: io_uring/cmd: fix iovec leak when the async cmd is not recycled Commit: b6a768aa975b9ca81b92f028bdd975d1f8237894 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=b6a768aa975b9ca81b92f028bdd975d1f8237894 Commit description: An io_async_cmd carries an iovec array in ->vec.iovec, allocated when the vec has to grow and kept across recycling through ctx->cmd_cache. On two paths nothing frees it and io_clean_op()'s kfree(req->async_data) drops the io_async_cmd without it. io_req_uring_cleanup() clears the async data flags only when io_alloc_cache_put() succeeds, and the cache holds IO_ALLOC_CACHE_MAX == 128 entries, so once it is full the put fails and the vec is left behind. An NVMe passthrough workload gets there without doing anything unusual: nvme_uring_cmd_io() returns -EIOCBQUEUED, so the io_async_cmd stays attached for the lifetime of the command and the live object count tracks the queue depth. Above 128 the puts start failing. ->cleanup is the last chance to free an inherited vec, since io_req_uring_cleanup() returns early for an io-wq issued command and is not called at all for one completed without ever being issued. But io_clean_op() calls ->cleanup only if REQ_F_NEED_CLEANUP is set, and for uring_cmd that happens only where the vec has to grow, so a command reusing a large enough cached vec never sets it. io_rw_alloc_async() and io_msg_alloc_async() flag an inherited vec for exactly this reason; io_uring_cmd_prep() does not. Flag an inherited vec in io_uring_cmd_prep(), and free the vec when the cache put fails, as io_req_rw_cleanup() does. The leak is invisible under KASAN, where io_alloc_cache_vec_kasan() frees the vec unconditionally. Fixes: 3a4689a ("io_uring/cmd: add iovec cache for commands") Cc: stable@vger.kernel.org Signed-off-by: Woraphat Khiaodaeng Link: https://patch.msgid.link/20260802073518.419-1-worapat.kd2@gmail.com Signed-off-by: Jens Axboe Signed-off-by: Greg Kroah-Hartman Changed files: io_uring/uring_cmd.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=b6a768aa975b9ca81b92f028bdd975d1f8237894 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-80811 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-80811 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:N/I:N/A:L The Best / paranoid CVSS vector: AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H The Best / paranoid CVSS score: 5.5 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: 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).