From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-45905][LOW] xfrm: fix ip_rt_bug race in icmp_route_lookup reverse path [ Upstream Date: Wed, 27 May 2026 22:06:49 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-45905 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: 0 X-AL-KERNEL-Commit: 9a95ec9144eeff1fc6fbcc21b677e322c6f1430b List-Id: CVE: CVE-2026-45905 Priority: LOW AL-KERNEL base severity: LOW KPANIC flag: NO Patch: xfrm: fix ip_rt_bug race in icmp_route_lookup reverse path [ Upstream Commit: 9a95ec9144eeff1fc6fbcc21b677e322c6f1430b Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=9a95ec9144eeff1fc6fbcc21b677e322c6f1430b Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-45905 Analysis date: Wed, 27 May 2026 22:06:49 -0400 ActionableScore: 2 ActionableScore lower bound: 0 Actionable bucket: Ordinary Moderate / Low-like Manual review required: NO Summary: An XFRM-aware ICMP route lookup race with local address changes can return an `RTN_LOCAL` route using `ip_rt_bug` as output, causing a WARN and possible `panic_on_warn` DoS. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-45905 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-45905 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-2026-45905 LOW 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:N/I:N/A:H';CWE-362;CWE-617;CWE-703;Other CVSS 'AV:L/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:L';BEST CVSS score: '4.7';DESCR 'An ICMP reverse path lookup bug in the XFRM aware route selection path can race with local address configuration changes. If an address becomes local between the locality check and ip_route_input(), the lookup can return an RTN_LOCAL route whose output handler is ip_rt_bug, and later ICMP output can trigger a WARN. For the CVSS the PR:L is used in the paranoid score because delegated CAP_NET_ADMIN inside a namespace or container can make address changes and route setup reachable below full host root, while typical reliable triggering requires host network administration privileges. The issue is not directly network reachable because packet traffic only helps exercise the ICMP path and the critical race needs local address configuration changes. Impact is denial of service through WARN or panic_on_warn behavior. No supported evidence indicates information disclosure, integrity impact, kernel memory corruption, or privilege escalation.';NO MANUAL CHECK; ,and ActionableScore result is Ordinary Moderate / Low-like (with actual score 1) MAYBE REMOTE OOB DANGER RACE NETWORK HARDWARE SYZBOT 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=0 ## 1. ActionableScore * Conservative score: 0 * Paranoid score: 2 * Final recommended bucket: **Ordinary Moderate / Low-like**:: ## 2. Signal breakdown * Availability impact realistic: +1 The demonstrated impact is a WARN via `ip_rt_bug()` during ICMP output. This can become DoS mainly when `panic_on_warn` is enabled. * Local delegated network administration trigger: +1 in paranoid scoring The race requires local address configuration changes such as `ip addr add`. This is normally `CAP_NET_ADMIN`, but may be delegated inside network namespaces or containers. * Hard race or special timing required: -1 The commit explicitly says the reproducer needs kernel modification to widen the race window, so practical triggering is difficult. * Requires CAP_NET_ADMIN in typical deployments: -2 conservative Reliable triggering requires local control over address configuration and routing state. * No direct remote reachability: +0 Packet traffic can exercise the ICMP path, but the critical race depends on local address configuration changes. * No memory corruption: +0 The patch prevents use of an `RTN_LOCAL` route with `dst.output = ip_rt_bug`. It does not indicate UAF, OOB write, arbitrary write, or object lifetime corruption. ## 3. Reachability analysis A local actor with network administration rights can attempt to trigger the bug by racing ICMP reverse path route lookup with address changes. In normal host deployments this requires `CAP_NET_ADMIN`. In container or namespace setups, delegated network administration could make the trigger reachable to a less privileged tenant or service. The issue is not remotely triggerable by packets alone. The packet path only helps reach `icmp_route_lookup()`, while the actual bug needs local route or address state changes in a narrow timing window. ## 4. Severity interpretation This behaves like Low or ordinary Moderate DoS. The realistic impact is WARN or `panic_on_warn` availability loss. There is no evidence of memory corruption, privilege escalation, information disclosure, or persistent integrity impact. The race is also difficult to reproduce under normal conditions. ## 5. One-sentence report phrase An XFRM-aware ICMP route lookup race with local address changes can return an `RTN_LOCAL` route using `ip_rt_bug` as output, causing a WARN and possible `panic_on_warn` DoS. ## 6. Manual review recommendation NO MANUAL CHECK NEEDED The issue is a local `CAP_NET_ADMIN` timing race with WARN-only impact and no demonstrated memory corruption, privilege escalation, or remote trigger. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: xfrm: fix ip_rt_bug race in icmp_route_lookup reverse path [ Upstream Commit: 9a95ec9144eeff1fc6fbcc21b677e322c6f1430b Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=9a95ec9144eeff1fc6fbcc21b677e322c6f1430b Changed files: net/ipv4/route.c net/ipv4/icmp.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=9a95ec9144eeff1fc6fbcc21b677e322c6f1430b ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-45905 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-45905 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: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: 0 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).