From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-74495][LOW] igbvf: Fix leak in TX DMA error cleanup Date: Sat, 15 Aug 2026 15:35:23 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-74495 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: 31089f4eab42e0fc248ec80c26f9b0bad59ba4cc List-Id: CVE: CVE-2026-74495 Priority: LOW AL-KERNEL base severity: LOW KPANIC flag: NO Patch: igbvf: Fix leak in TX DMA error cleanup Commit: 31089f4eab42e0fc248ec80c26f9b0bad59ba4cc Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=31089f4eab42e0fc248ec80c26f9b0bad59ba4cc Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74495 Analysis date: Sat, 15 Aug 2026 15:35:23 -0400 ActionableScore: 2 ActionableScore lower bound: 1 Actionable bucket: Ordinary Moderate / Low-like Manual review required: NO Summary: An off by one error in igbvf TX DMA error cleanup can leak one DMA mapping after a partial TX mapping failure, potentially causing resource exhaustion DoS under repeated failure conditions, but no memory corruption or privilege escalation primitive is evident. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-74495 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74495 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-2026-74495 LOW 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-772;*CWE-401;CWE-459;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '4.7';DESCR 'An off by one error in the igbvf TX DMA error cleanup path can leave one DMA mapping unreleased when mapping TX buffers fails after at least one mapping succeeded. This is a resource leak in the transmit path rather than a direct memory corruption primitive. For the CVSS the PR:L is used because a local unprivileged process may be able to generate traffic through the affected interface, but reliable triggering also requires DMA mapping failures or resource pressure. The issue is not directly network reachable because the vulnerable cleanup is exercised by local TX processing and error handling, not by parsing inbound packets. Impact is denial of service through possible DMA or IOMMU resource exhaustion after repeated failures, with no supported confidentiality or integrity impact.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like (with actual score 2) SKIP CVE-2026-74495 UNKNOWN SKIP The Fixes patch not applied yet, so unlikely that actual: c1fa347f20f17f14a4a1575727fa24340e8a9117 YES NO NO unknown MAYBE REMOTE LEAK NETWORK DMAorINTERRUPT TEST MEMORY PACKET DECREASED_TO_MODERATE_REGULAR_FROM_MODERATE7_BASED_ON_GUESSCVSS_AND_CIANNH DECREASED_TO_LOW_FROM_MODERATE_BASED_ON_ACTIONABLESCORELESSTHAN3 - - 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. A local process may generate TX traffic through the affected igbvf interface. * Hard or unreliable trigger: -1. The leak only occurs if TX DMA mapping fails after at least one successful mapping, which usually requires resource pressure or unusual DMA/IOMMU conditions. * Availability impact realistic: +1. Repeated leaks could theoretically exhaust DMA/IOMMU mappings, but this is cumulative and not an immediate reliable crash. Paranoid additional interpretation: * Reliable kernel crash / strong DoS: +1. Counted only in the paranoid score if repeated TX mapping failures can realistically accumulate leaked DMA mappings until device or host networking availability is affected. Not awarded: * No generic memory corruption. The patch fixes a DMA mapping leak, not UAF, double free, OOB write, type confusion, or arbitrary write. * No privilege escalation plausible. There is no reclaim, overwrite, stale callback, refcount takeover, or attacker-controlled object replacement. * No confidentiality or integrity impact. The described primitive is resource leakage only. * No remote reachable signal. The vulnerable path is TX DMA error cleanup, not parsing inbound network packets. ## 3. Reachability analysis A local user may be able to exercise the TX path by sending traffic through an affected igbvf virtual function. However, reliable triggering also requires DMA mapping failure after partial successful mapping, which is not normally under direct attacker control. Namespaces or containers may allow traffic generation through the interface, but they do not remove the need for the unusual DMA failure condition. The issue is device and configuration dependent because it requires the Intel igbvf driver and affected virtual function deployment. Call-site confidence: medium. The function and error path are visible, but broader runtime behavior depends on DMA mapping failure conditions outside the provided diff. ## 4. Severity interpretation This behaves like an ordinary Moderate or Low-like resource leak, not an Important-class vulnerability. The theoretical worst case is denial of service through accumulated DMA or IOMMU resource exhaustion. Realistic exploitation evidence is weak because the attacker must repeatedly hit a partial TX DMA mapping failure window. There is no supported memory corruption or privilege escalation primitive. ## 5. One-sentence report phrase An off by one error in igbvf TX DMA error cleanup can leak one DMA mapping after a partial TX mapping failure, potentially causing resource exhaustion DoS under repeated failure conditions, but no memory corruption or privilege escalation primitive is evident. ## 6. Manual review recommendation NO MANUAL CHECK NEEDED This can be auto-closed or handled as low-priority Moderate unless the product has evidence that untrusted users can reliably force TX DMA mapping failures on affected igbvf devices. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: igbvf: Fix leak in TX DMA error cleanup Commit: 31089f4eab42e0fc248ec80c26f9b0bad59ba4cc Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=31089f4eab42e0fc248ec80c26f9b0bad59ba4cc Commit description: If an error is encountered while mapping TX buffers, the driver should unmap any buffers already mapped for that skb. Because count is incremented before each frag mapping, it will always match the correct number of unmappings needed when dma_error is reached. Decrementing count before the while loop in dma_error causes an off-by-one error. If any mapping was successful before an unsuccessful mapping, exactly one DMA mapping (the head) would leak. This bug was introduced by a 2010 fix for an endless loop in dma_error. All other affected drivers have already been fixed. Fixes: c1fa347 ("e1000/e1000e/igb/igbvf/ixgb/ixgbe: Fix tests of unsigned in *_tx_map()") Cc: stable@vger.kernel.org Assisted-by: Claude:claude-4-7-opus Signed-off-by: Matt Vollrath Signed-off-by: Tony Nguyen Signed-off-by: Greg Kroah-Hartman Changed files: drivers/net/ethernet/intel/igbvf/netdev.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=31089f4eab42e0fc248ec80c26f9b0bad59ba4cc ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-74495 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-74495 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:N/I:N/A:L 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: 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).