From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-64122][MODERATE 7.0] net/mlx5e: Fix use-after-free in mlx5e_tx_reporter_timeout_recover Date: Sun, 19 Jul 2026 21:32:43 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-64122 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: 5 X-AL-KERNEL-ActionableScore-Lower: 4 X-AL-KERNEL-Commit: 1604a2d68414aa4cc34faac0b7faa9c14455e8d3 List-Id: CVE: CVE-2026-64122 Priority: MODERATE 7.0 AL-KERNEL base severity: MODERATE KPANIC flag: YES Patch: net/mlx5e: Fix use-after-free in mlx5e_tx_reporter_timeout_recover Commit: 1604a2d68414aa4cc34faac0b7faa9c14455e8d3 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=1604a2d68414aa4cc34faac0b7faa9c14455e8d3 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64122 Analysis date: Sun, 19 Jul 2026 21:32:43 -0400 ActionableScore: 5 ActionableScore lower bound: 4 Actionable bucket: Actionable Moderate at minimum Manual review required: YES Summary: A use-after-free in mlx5e TX timeout recovery can occur when recovery code dereferences `sq->netdev` after channel teardown frees the SQ, leading to a kernel crash and requiring manual review due to confirmed lifetime corruption. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-64122 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64122 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-2026-64122 MODERATE CHECK WITH IMPACT FROM ORIG NN MODERATE Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:H';*CWE-416;CWE-362;CWE-825;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '5.8';DESCR 'A use after free can occur in the mlx5e TX timeout recovery path because mlx5e_tx_reporter_timeout_recover accesses sq netdev after mlx5e_safe_reopen_channels may have torn down and freed the channel containing that SQ. The observed failure is a KASAN UAF read in a workqueue recovery path and the most realistic impact is a kernel crash or driver recovery failure. For the CVSS the PR:L is used for the paranoid score because a local user or process may be able to create TX activity and help reach the timeout recovery path, although reliable triggering still depends on device state and a race window. The issue is not directly network reachable as a packet processing bug and is not expected to be triggered simply by remote inbound traffic. Impact is at least local denial of service via kernel crash and in worst case may allow limited confidentiality or integrity impact due to UAF memory reuse, so it should be reviewed manually.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate at minimum (with actual score 5) SKIP CVE-2026-64122 UNKNOWN SKIP No affected files built, so skip this CVE NO - - unknown MAYBE REMOTE READ DEADLOCK DANGER UAF NETWORK KPANIC - - checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=5 ActionableScoreLower=4 ## 1. ActionableScore * Conservative score: 4 * Paranoid score: 5 * Final recommended bucket: **Actionable Moderate at minimum**:: ## 2. Signal breakdown Conservative signals: * Memory corruption, weak primitive: +1 Confirmed KASAN use-after-free read of `sq->netdev`, but no shown attacker-controlled reclaim, write-after-free, callback control, type confusion, or arbitrary write. * Real lifetime corruption: +1 `sq` belongs to a channel that may be torn down and freed by `mlx5e_safe_reopen_channels()`, while recovery code still dereferences it. * Reliable kernel crash / strong DoS: +1 The commit includes a KASAN UAF splat in a workqueue recovery path. * Local unprivileged trigger plausible: +1 A local process may be able to generate TX activity and contribute to TX timeout conditions, although reliable triggering depends on NIC and recovery state. * Broad deployed driver exposure: +1 mlx5e is common in server and data-center environments. * Hard race / special timing required: -1 The bug depends on TX timeout recovery racing with channel teardown/reopen. Paranoid additional signal: * Privileged kernel/device-management lifetime path: +1 The stale object is used inside NIC health recovery and channel management code, so the bug deserves manual review even though attacker control appears weak. Race-UAF cap applied: * Conservative score capped at 4. * Paranoid score capped at 5. ## 3. Reachability analysis This is not directly network-reachable as a normal packet parsing or RX path vulnerability. The affected path is mlx5e TX timeout recovery through devlink health reporting and workqueue execution. A local process can plausibly create TX load, but reaching the vulnerable window likely requires a TX timeout, channel reopen or teardown, and specific device or driver state. Namespaces and containers may affect practical reachability. An unprivileged container that can only send traffic has limited control, while a process with delegated network administration or device-management capability may be better positioned to trigger resets or recovery. The path is enabled only on systems using mlx5e hardware and the affected driver, but this hardware is common in production data-center deployments. Call-site confidence: high. The patch and stack trace show the relevant recovery call path and the exact stale dereference. ## 4. Severity interpretation This behaves more like an actionable Moderate than an ordinary Moderate because it is a confirmed kernel UAF in a widely deployed network driver recovery path. It is not a strong Important candidate based on the provided evidence because the demonstrated primitive is a stale read of `sq->netdev`, with no shown reclaim control, write primitive, object replacement, callback dispatch, or privilege-escalation chain. The realistic impact is kernel crash or driver recovery failure. The theoretical memory-corruption concern is sufficient for manual review, but the patch does not support treating this as a likely LPE or remote compromise. ## 5. One-sentence report phrase A use-after-free in mlx5e TX timeout recovery can occur when recovery code dereferences `sq->netdev` after channel teardown frees the SQ, leading to a kernel crash and requiring manual review due to confirmed lifetime corruption. ## 6. Manual review recommendation MANUAL CHECK REQUIRED Reason: confirmed UAF in kernel driver recovery code, KASAN evidence, and common data-center hardware exposure, even though the currently demonstrated impact is mainly DoS and the exploitability path is timing-dependent. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: net/mlx5e: Fix use-after-free in mlx5e_tx_reporter_timeout_recover Commit: 1604a2d68414aa4cc34faac0b7faa9c14455e8d3 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=1604a2d68414aa4cc34faac0b7faa9c14455e8d3 Commit description: mlx5e_tx_reporter_timeout_recover() accesses sq->netdev after mlx5e_safe_reopen_channels() has torn down and freed the channel (and its embedded SQs). Replace the three sq->netdev references with priv->netdev which is safe because priv outlives channel teardown. The netdev_err() call already used priv->netdev for this reason; make the trylock/unlock and health_channel_eq_recover calls consistent. This fixes the following KASAN splat: BUG: KASAN: use-after-free in mlx5e_tx_reporter_timeout_recover+0x1dd/0x360 [mlx5_core] Read of size 8 at addr ffff889860ed0b28 by task kworker/u113:2/5277 Call Trace: mlx5e_tx_reporter_timeout_recover+0x1dd/0x360 [mlx5_core] devlink_health_reporter_recover+0xa2/0x150 devlink_health_report+0x254/0x7c0 mlx5e_reporter_tx_timeout+0x297/0x380 [mlx5_core] mlx5e_tx_timeout_work+0x109/0x170 [mlx5_core] process_one_work+0x677/0xf20 worker_thread+0x51f/0xd90 kthread+0x3a5/0x810 ret_from_fork+0x208/0x400 ret_from_fork_asm+0x1a/0x30 Fixes: 83ac030 ("net/mlx5e: Fix deadlocks between devlink and netdev instance locks") Cc: stable@vger.kernel.org Reviewed-by: Cosmin Ratiu Reviewed-by: Tariq Toukan Signed-off-by: Matt Fleming Link: https://patch.msgid.link/20260513112226.140512-1-matt@readmodwrite.com Signed-off-by: Jakub Kicinski Signed-off-by: Greg Kroah-Hartman Changed files: drivers/net/ethernet/mellanox/mlx5/core/en/reporter_tx.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=1604a2d68414aa4cc34faac0b7faa9c14455e8d3 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-64122 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64122 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:H The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:H The Best / paranoid CVSS score: 5.8 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: 4 Paranoid ActionableScore: 5 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).