From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-63837][MODERATE REGULAR] net: ena: PHC: Check return code before setting timestamp output Date: Sun, 19 Jul 2026 11:42:36 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-63837 X-AL-KERNEL-Priority: MODERATE REGULAR X-AL-KERNEL-Severity: MODERATE REGULAR X-AL-KERNEL-Base-Severity: MODERATE X-AL-KERNEL-KPANIC: NO X-AL-KERNEL-ActionableScore: 3 X-AL-KERNEL-ActionableScore-Lower: unknown X-AL-KERNEL-Commit: bddf59818ae5102e6d82a4dae5add6df8da38fb0 List-Id: CVE: CVE-2026-63837 Priority: MODERATE REGULAR AL-KERNEL base severity: MODERATE KPANIC flag: NO Patch: net: ena: PHC: Check return code before setting timestamp output Commit: bddf59818ae5102e6d82a4dae5add6df8da38fb0 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=bddf59818ae5102e6d82a4dae5add6df8da38fb0 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-63837 Analysis date: Sun, 19 Jul 2026 11:42:36 -0400 ActionableScore: 3 ActionableScore lower bound: unknown Actionable bucket: Borderline, manual review recommended Manual review required: YES Summary: `ena_phc_gettimex64() could copy an uninitialized or invalid timestamp value to userspace after a failed PHC timestamp read, creating a local information disclosure through the ENA PTP ioctl path.` ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-63837 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-63837 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 REGULAR 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-2026-63837 MODERATE 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:H/I:N/A:N';*CWE-200;*CWE-457;CWE-665;Other CVSS 'AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N';BEST CVSS score: '5.5';DESCR 'ena_phc_gettimex64() could return a timestamp to userspace even when ena_com_phc_get_timestamp() failed. In that error path the timestamp value may contain uninitialized kernel stack data or invalid hardware data, which makes the issue a local information disclosure through the ENA PHC and PTP time query path. For the CVSS the PR:L is used because a local user or process needs access to the PTP clock interface or related device node, even if no administrative capability is necessarily required on systems with permissive device permissions. The issue is not network reachable and does not by itself provide a write primitive or a kernel crash. Impact is confidentiality only, with base C:L and paranoid C:H because repeated exposure of uninitialized kernel stack data may disclose sensitive values useful for later attacks.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline, manual review recommended (with actual score 3) YES REMOTE SIMPLEFIX LEAK NETWORK HARDWARE LINUS DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5 YES NO checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=3 ## 1. ActionableScore * Conservative score: 3 * Paranoid score: 4 * Final recommended bucket: **Borderline, manual review recommended**:: ## 2. Signal breakdown Triggered signals: * Local unprivileged trigger: +1 A local process that can access the ENA PHC/PTP device path can trigger the PTP time query path. This is not remote network traffic. * Confidentiality impact plausible: +1 The commit explicitly states that uninitialized stack memory or invalid hardware-derived values may be copied to userspace. * Broad/cloud-relevant device exposure: +1 ENA is common in AWS-style virtualized/cloud deployments, although PHC/PTP exposure depends on device support and configuration. Paranoid-only signal: * Kernel stack information leak sensitivity: +1 Repeated disclosure of uninitialized stack data can sometimes expose useful kernel values. This does not prove LPE, but it is enough to avoid auto-close without review. Not triggered: * No generic memory corruption. * No UAF, double-free, OOB write, arbitrary write, or refcount/lifetime primitive. * No reliable kernel crash. * No network-triggerable path. * No direct integrity impact. * No demonstrated privilege escalation. ## 3. Reachability analysis The bug is reachable through the local PTP ioctl path for the ENA PHC device. A local user or service needs access to the relevant `/dev/ptpX` device or equivalent PHC interface, so PR:L is the practical model. It is not triggered by ordinary network packets and should not be treated as remotely reachable. Namespaces or containers may matter only if the PTP device is passed through or exposed into the container. In default hardened deployments, access to PHC/PTP device nodes may be restricted by permissions, device cgroups, or container policy. In cloud environments using ENA with PHC enabled, the affected driver is relevant, but exploitation still requires local device-interface access. ## 4. Severity interpretation This behaves like a local information disclosure, not memory corruption and not a standalone privilege-escalation bug. The realistic impact is leakage of a timestamp-sized value that may contain uninitialized kernel stack data when timestamp retrieval fails. Theoretical impact is higher than an ordinary correctness bug because kernel stack disclosure can help defeat mitigations or aid later exploit chains. However, the patch does not show a write primitive, object lifetime issue, crash path, or direct LPE primitive. Therefore this is best treated as borderline/actionable Moderate rather than Important. ## 5. One-sentence report phrase `ena_phc_gettimex64() could copy an uninitialized or invalid timestamp value to userspace after a failed PHC timestamp read, creating a local information disclosure through the ENA PTP ioctl path.` ## 6. Manual review recommendation MANUAL CHECK RECOMMENDED This should not be auto-closed because the commit explicitly describes a kernel information leak involving possibly uninitialized stack memory. The issue is still below Important in the conservative assessment because there is no memory corruption, no crash, no remote reachability, and no demonstrated privilege-escalation primitive. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: net: ena: PHC: Check return code before setting timestamp output Commit: bddf59818ae5102e6d82a4dae5add6df8da38fb0 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=bddf59818ae5102e6d82a4dae5add6df8da38fb0 Commit description: ena_phc_gettimex64() is setting the output parameter regardless of whether ena_com_phc_get_timestamp() succeeded or failed. When ena_com_phc_get_timestamp() returns an error, the timestamp parameter may contain uninitialized stack memory (e.g., when PHC is disabled or in blocked state) or invalid hardware values. Passing these to userspace via the PTP ioctl is both a security issue (information leak) and a correctness bug. Fix by checking the return code after releasing the lock and only setting the output timestamp on success. 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/20260507003518.22554-1-akiyano@amazon.com Signed-off-by: Jakub Kicinski Signed-off-by: Greg Kroah-Hartman Changed files: drivers/net/ethernet/amazon/ena/ena_phc.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=bddf59818ae5102e6d82a4dae5add6df8da38fb0 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-63837 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-63837 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:L/I:N/A:N The Best / paranoid CVSS vector: AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N 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: unknown Paranoid ActionableScore: 3 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: NO Published priority for this report (same as in Subject): MODERATE REGULAR 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).