From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-72072][MODERATE 7.0] net/mlx5e: macsec: fix use-after-free of metadata_dst on RX SC delete commit de74d8fd10291763d97b218f09adcc7513c975e4 upstream. Date: Sun, 16 Aug 2026 02:38:10 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-72072 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: b1a4d0c568bbb52c7c04f4fce3c097dae89ed6cb List-Id: CVE: CVE-2026-72072 Priority: MODERATE 7.0 AL-KERNEL base severity: MODERATE KPANIC flag: YES Patch: net/mlx5e: macsec: fix use-after-free of metadata_dst on RX SC delete commit de74d8fd10291763d97b218f09adcc7513c975e4 upstream. Commit: b1a4d0c568bbb52c7c04f4fce3c097dae89ed6cb Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=b1a4d0c568bbb52c7c04f4fce3c097dae89ed6cb Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72072 Analysis date: Sun, 16 Aug 2026 02:38:10 -0400 ActionableScore: 5 ActionableScore lower bound: 4 Actionable bucket: Strong Important candidate / Actionable Moderate at minimum Manual review required: YES Summary: A race in mlx5e MACsec RX offload can free metadata_dst while the RX datapath still loads and attaches it to an skb, creating a UAF that can crash the kernel and may warrant Important level manual review in deployments with delegated network administration. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-72072 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72072 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-2026-72072 MODERATE CHECK WITH IMPACT FROM ORIG NN LOW Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:A/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H';*CWE-416;CWE-362;*CWE-664;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:L/I:L/A:H';BEST CVSS score: '7.1';DESCR 'A use-after-free can occur in the mlx5e MACsec RX offload path when RX SC deletion races with packet processing. The delete path used metadata_dst_free and could free the per SC metadata_dst without respecting dst references, while mlx5e_macsec_offload_handle_rx_skb() could already have loaded the SC through xa_load() under rcu_read_lock() and then attach the dst to an skb. This can lead to a kernel crash and in the worst case may create a memory corruption condition in the networking datapath. For the CVSS the PR:L is used for the paranoid score because delegated CAP_NET_ADMIN, container root, or a network management service account may be enough to delete or reconfigure MACsec RX SC state in some deployments. The issue is not Internet routed AV:N and is better treated as adjacent network plus local control plane exposure because MACsec operates at L2 and requires mlx5e MACsec offload to be configured. Impact is at least denial of service via kernel crash and in worst case may allow confidentiality or integrity impact due to UAF based memory corruption.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Strong Important candidate / Actionable Moderate at minimum (with actual score 5) SKIP CVE-2026-72072 UNKNOWN SKIP No affected files built, so skip this CVE NO - - unknown MAYBE REMOTE LOCK INIT RACE ERRORPATH UAF NETWORK SKB HARDWARE KPANIC - - checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=5 ActionableScoreLower=4 ## 1. ActionableScore * Conservative score: 4 * Paranoid score: 5 * Final recommended bucket: **Strong Important candidate / Actionable Moderate at minimum**:: ## 2. Signal breakdown Conservative scoring: * Memory corruption, weak or race dependent UAF primitive: +1. The patch fixes a real use after free of metadata_dst, but no attacker controlled reclaim, type confusion, overwrite, or callback control is demonstrated. * Real lifetime corruption: +1. metadata_dst_free ignored dst refcount while RX code could still hold or acquire the object. * Reliable kernel crash / strong DoS: +1. A freed dst can be attached to skb and later used by the RX path, making kernel crash realistic. * Privileged kernel/device management memory corruption path: +1. The bug is in mlx5e MACsec offload driver state and skb metadata ownership handling. * Hard or unreliable race / special timing required: -1. Trigger depends on RX SC deletion racing RX packet processing. * Requires CAP_NET_ADMIN or equivalent in typical deployments: -1 in practical scoring. Full -2 is possible for strict host admin only, but delegated network management, container root with network capabilities, or service accounts make the effective privilege boundary weaker. Conservative subtotal: 4. Paranoid scoring: * Same as above, plus adjacent network datapath influence: +1. Packet processing on the RX datapath can participate in the race once MACsec offload is configured. * Race UAF downgrade cap applies. No concrete reclaim or write primitive is shown, so paranoid score is capped at 5. Paranoid subtotal: 5. ## 3. Reachability analysis The vulnerable path requires mlx5e MACsec RX offload to be configured and an RX Secure Channel to be deleted while MACsec RX traffic is being handled. In typical deployments, RX SC deletion requires CAP_NET_ADMIN or a privileged network control plane, so this is not a normal unprivileged local trigger. However, the practical privilege model may be weaker in environments using delegated CAP_NET_ADMIN, containerized network management, orchestration agents, or reduced capability service accounts. The bug is not Internet routable AV:N. MACsec is L2 adjacent and hardware or driver specific. An adjacent peer can help exercise the RX datapath with traffic, but the key state transition is local control plane deletion of the RX SC. The affected configuration is not universal, but mlx5e is a high value datacenter NIC driver and the bug affects packet handling plus object lifetime semantics. Call-site confidence: high. The patch includes both the delete path and the RX datapath call site. ## 4. Severity interpretation This is more than an ordinary Moderate cleanup bug because the patch fixes a concrete UAF and refcount lifetime error in a network RX datapath. Realistic exploitation evidence supports kernel crash or DoS most strongly. Privilege escalation is not demonstrated because there is no shown attacker controlled reclaim, object replacement, function pointer control, write after free, or type confusion. The best practical interpretation is Actionable Moderate with manual review required. A Strong Important candidate label is defensible for triage sensitivity because the bug is a real UAF in networking driver packet handling and the commit also notes a separate remaining RCU lifetime issue. ## 5. One-sentence report phrase A race in mlx5e MACsec RX offload can free metadata_dst while the RX datapath still loads and attaches it to an skb, creating a UAF that can crash the kernel and may warrant Important level manual review in deployments with delegated network administration. ## 6. Manual review recommendation MANUAL CHECK REQUIRED This should not be auto-closed because it is a concrete network datapath UAF involving dst refcount lifetime, RCU lookup, skb metadata attachment, and a remaining related RCU lifetime issue noted by the commit. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: net/mlx5e: macsec: fix use-after-free of metadata_dst on RX SC delete commit de74d8fd10291763d97b218f09adcc7513c975e4 upstream. Commit: b1a4d0c568bbb52c7c04f4fce3c097dae89ed6cb Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=b1a4d0c568bbb52c7c04f4fce3c097dae89ed6cb Commit description: When an offloaded MACsec RX SC is deleted, macsec_del_rxsc_ctx() freed the per-SC metadata_dst with metadata_dst_free(), which kfree()s the object unconditionally and ignores the dst reference count. The RX datapath in mlx5e_macsec_offload_handle_rx_skb() looks up the SC under rcu_read_lock() via xa_load(), takes a reference with dst_hold() and attaches the dst to the skb with skb_dst_set(). A reader that already obtained the rx_sc pointer can race with the delete path and operate on freed memory. Fix the owner side by dropping the reference with dst_release() instead of freeing unconditionally, and convert the RX datapath to dst_hold_safe() so a reader racing the SC delete cannot attach a dst whose last reference was just dropped; only attach it when a reference was actually taken. mlx5e_macsec_add_rxsc() also published sc_xarray_element via xa_alloc() before rx_sc->md_dst was allocated and initialised, so a datapath reader that looked the SC up by fs_id could observe rx_sc with md_dst still NULL or, on weakly-ordered architectures, a non-NULL md_dst pointer whose contents were not yet visible. NULL-check the xa_load() result and md_dst on the datapath, and reorder add_rxsc() so the xa_alloc() publish happens only after md_dst is fully initialised; the xarray RCU publish then pairs with the rcu_read_lock()/xa_load() in the datapath. Note: macsec_del_rxsc_ctx() also kfree()s rx_sc->sc_xarray_element without an RCU grace period while the same datapath reads it under rcu_read_lock(); that is a separate pre-existing issue left to a follow-up patch. Found by 0sec automated security-research tooling (https://0sec.ai). Fixes: b7c9400cbc48 ("net/mlx5e: Implement MACsec Rx data path using MACsec skb_metadata_dst") Cc: stable@vger.kernel.org Signed-off-by: Doruk Tan Ozturk Reviewed-by: Tariq Toukan Link: https://patch.msgid.link/20260627223059.29917-1-doruk@0sec.ai Signed-off-by: Jakub Kicinski Signed-off-by: Greg Kroah-Hartman Diffstat -rw-r--r-- drivers/net/ethernet/mellanox/mlx5/core/en_accel/macsec.c 47 Changed files: drivers/net/ethernet/mellanox/mlx5/core/en_accel/macsec.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=b1a4d0c568bbb52c7c04f4fce3c097dae89ed6cb ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-72072 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-72072 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:H/UI:N/S:U/C:L/I:L/A:H The Best / paranoid CVSS vector: AV:A/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H 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: 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).