From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-52971][MODERATE 7.0] net: ena: PHC: Fix potential use-after-free in get_timestamp Date: Thu, 25 Jun 2026 17:04:17 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-52971 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: 6 X-AL-KERNEL-ActionableScore-Lower: 4 X-AL-KERNEL-Commit: 95e8ae9af2a61b4e72f5c585bf4c7d8aaf2a2c98 List-Id: CVE: CVE-2026-52971 Priority: MODERATE 7.0 AL-KERNEL base severity: MODERATE KPANIC flag: YES Patch: net: ena: PHC: Fix potential use-after-free in get_timestamp Commit: 95e8ae9af2a61b4e72f5c585bf4c7d8aaf2a2c98 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=95e8ae9af2a61b4e72f5c585bf4c7d8aaf2a2c98 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-52971 Analysis date: Thu, 25 Jun 2026 17:04:17 -0400 ActionableScore: 6 ActionableScore lower bound: 4 Actionable bucket: Actionable Moderate at minimum Manual review required: YES Summary: A race in ENA PHC timestamp handling can let `get_timestamp()` use a stale DMA-backed response pointer after PHC destruction, causing a local kernel crash and presenting a weak UAF-based privilege-escalation concern that requires manual review. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-52971 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-52971 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-2026-52971 MODERATE CHECK Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H';CWE-362;*CWE-416;**CWE-476;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '7';DESCR 'ENA PHC timestamp handling has a race where phc active is checked and the response pointer is read without holding the PHC spinlock. If ena_com_phc_destroy runs in the same window, it can mark PHC inactive and free the DMA backed response buffer while get_timestamp still uses a stale or NULL pointer. For the CVSS the PR:L is used because triggering requires local code reaching the PHC timestamp path, such as access to the PTP clock or a driver path that calls get_timestamp, while the concurrent destroy or reset condition creates a high complexity race. The issue is not directly network reachable. Base impact is local denial of service via kernel crash. In the paranoid view, stale DMA memory referenced by a cached response pointer is a use after free memory corruption candidate, so C:H/I:H/A:H is defensible for manual review.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate at minimum (with actual score 5) MAYBE REMOTE LOCK UAF NETWORK DMAorINTERRUPT HARDWARE LINUS KPANIC - - checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=6 ActionableScoreLower=4 ## 1. ActionableScore * Conservative score: 4 * Paranoid score: 6 * Final recommended bucket: **Actionable Moderate at minimum**:: ## 2. Signal breakdown Paranoid score signals: * Generic memory corruption: +2. The patch fixes a stale pointer / potential UAF race on `ena_dev->phc.virt_addr`, which points to DMA-backed memory. * Real lifetime corruption: +1. `ena_com_phc_destroy()` can free the PHC DMA memory while `ena_com_phc_get_timestamp()` still uses the cached pointer. * Reliable kernel crash / strong DoS: +1. The described failure can dereference freed or NULL memory in kernel context. * Weak LPE concern: +1. UAF on driver/DMA-backed memory can be more than DoS in theory, but the patch does not show a controlled reclaim or overwrite primitive. * Privileged kernel/device-management memory corruption path: +1. The bug is in an Ethernet driver PHC path involving device state, DMA memory, and teardown/reset. * Hard or unreliable race: -1. Exploitation requires a timing window between timestamp retrieval and PHC destroy/reset. Conservative score additionally treats reliable triggering as likely requiring privileged reset/remove/teardown control in typical deployments, effectively reducing practical exploitability. ## 3. Reachability analysis The bug is not directly network reachable. A local process must reach the ENA PHC timestamp path, for example through PTP clock access or a driver path that calls `get_timestamp()`. The dangerous race also requires concurrent PHC destruction, device teardown, reset, or similar lifecycle transition. In typical deployments, forcing device teardown or reset is privileged. However, PTP access may be delegated to service accounts, containers, or time-sync daemons, and ENA is common in cloud environments. That makes PR:L a defensible paranoid interpretation, while conservative practical triggering may require administrative control over the device lifecycle. ## 4. Severity interpretation This is stronger than an ordinary Moderate because the patch explicitly fixes a lifetime race with a potential use-after-free, not just a warning or simple NULL check. Realistic impact is most clearly local DoS via kernel crash. Privilege escalation is not demonstrated, but the stale DMA-backed pointer makes manual review appropriate because UAF-class driver bugs can be underestimated during initial triage. Overall this is an Actionable Moderate at minimum, with Important-candidate concern only if further analysis shows local unprivileged access to the timestamp path plus a realistic way to trigger reset/destroy and influence memory reuse. ## 5. One-sentence report phrase A race in ENA PHC timestamp handling can let `get_timestamp()` use a stale DMA-backed response pointer after PHC destruction, causing a local kernel crash and presenting a weak UAF-based privilege-escalation concern that requires manual review. ## 6. Manual review recommendation MANUAL CHECK REQUIRED Reason: the patch explicitly fixes a potential UAF/lifetime race in a kernel network driver with DMA-backed memory, and the realistic privilege boundary depends on deployment-specific PTP device permissions and reset/teardown reachability. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: net: ena: PHC: Fix potential use-after-free in get_timestamp Commit: 95e8ae9af2a61b4e72f5c585bf4c7d8aaf2a2c98 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=95e8ae9af2a61b4e72f5c585bf4c7d8aaf2a2c98 Commit description: Move the phc->active check and resp pointer assignment to after acquiring the spinlock. Previously, phc->active was checked without holding the lock, and resp was cached from ena_dev->phc.virt_addr before the lock was acquired. If ena_com_phc_destroy() runs between the lockless active check and the lock acquisition, it sets active=false, releases the lock, frees the DMA memory, and sets virt_addr=NULL. The get_timestamp path would then read a NULL virt_addr and dereference it. With both the active check and the pointer read under the lock, destroy cannot free the memory while get_timestamp is using it. Fixes: e0ea341 ("net: ena: Add PHC support in the ENA driver") Cc: stable@vger.kernel.org Signed-off-by: Arthur Kiyanovski Reviewed-by: Vadim Fedorenko Link: https://patch.msgid.link/20260508062126.7273-1-akiyano@amazon.com Signed-off-by: Jakub Kicinski Signed-off-by: Greg Kroah-Hartman Changed files: drivers/net/ethernet/amazon/ena/ena_com.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=95e8ae9af2a61b4e72f5c585bf4c7d8aaf2a2c98 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-52971 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-52971 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:H/I:H/A:H The Best / paranoid CVSS score: 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: 4 Paranoid ActionableScore: 6 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).