From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-53249][MODERATE 7.0] ipv4: restrict IPOPT_SSRR and IPOPT_LSRR options [ Upstream Date: Thu, 25 Jun 2026 09:18:21 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-53249 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: 4cd6e9ed49347d3a2fdaaf07e32fb524756dddc2 List-Id: CVE: CVE-2026-53249 Priority: MODERATE 7.0 AL-KERNEL base severity: MODERATE KPANIC flag: YES Patch: ipv4: restrict IPOPT_SSRR and IPOPT_LSRR options [ Upstream Commit: 4cd6e9ed49347d3a2fdaaf07e32fb524756dddc2 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=4cd6e9ed49347d3a2fdaaf07e32fb524756dddc2 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53249 Analysis date: Thu, 25 Jun 2026 09:18:21 -0400 ActionableScore: 5 ActionableScore lower bound: 4 Actionable bucket: Actionable Moderate at minimum Manual review required: NO Summary: Unprivileged IPv4 sockets could set LSRR or SSRR source routing options without CAP_NET_RAW, allowing a local user to route packets through attacker controlled nodes and potentially expose TCP ISN or related protocol metadata when the network path accepts source routed packets. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-53249 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53249 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: NO A detailed explanation of the methodology and priority rules is included at the end of this message. ====================================================================== AL-KERNEL CLASSIFICATION RESULT ====================================================================== CVE-2026-53249 MODERATE CHECK Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N';CWE-862;CWE-284;*CWE-200;Other CVSS 'AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:N/A:N';BEST CVSS score: '4.4';DESCR 'Unprivileged IPv4 sockets could set LSRR or SSRR source routing options without CAP_NET_RAW, allowing a local user to force their own packets through attacker controlled network nodes. This may expose TCP ISN values or other protocol metadata that would normally require stronger network privileges to observe. For the CVSS the PR:L is used because a local unprivileged process is required to set the IP options and trigger the behavior. The issue is not directly network reachable as a remote packet processing bug, but the security impact depends on the network path accepting source routed IPv4 packets. Impact is mainly limited confidentiality exposure and possible limited integrity or routing policy impact, not kernel memory corruption or privilege escalation.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate at minimum (with actual score 5) YES REMOTE SIMPLEFIX LEAK NETWORK KPANIC PACKET KPANIC LOWERED_FROM_HIGH_BASED_ON_GUESSCVSS NO NO 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: * Local unprivileged trigger: +1. An unprivileged local process can set IPv4 LSRR or SSRR options before this patch. * Security-boundary bypass with practical protocol exposure: +2. The patch adds a CAP_NET_RAW check, so the old behavior bypassed an intended capability boundary for source-routed packets. * Confidentiality impact plausible: +1. The commit explicitly mentions leakage of TCP ISN and possibly other protocol information. * Broad/default networking subsystem: +1. The affected code is in the IPv4 socket option handling path. * Network-path filtering and legacy option constraints: -1. LSRR and SSRR are commonly filtered and often unusable across real networks. Paranoid additional signal: * Limited integrity or routing policy impact plausible: +1. If source routing is accepted on the path, an attacker may influence packet routing through attacker-controlled nodes, which can be treated as limited integrity or policy impact. No memory corruption, UAF, OOB access, kernel crash, or privilege escalation primitive is supported by the patch. ## 3. Reachability analysis The bug is triggered locally by a process that can create IPv4 sockets and set IP options. It is not a remote packet-processing vulnerability because the attacker must run code on the affected host to request LSRR or SSRR options. Namespaces matter because the new check uses `ns_capable(net->user_ns, CAP_NET_RAW)`. Before the fix, an unprivileged process in the relevant network namespace could set these options without that capability. The practical impact depends heavily on whether the surrounding network forwards IPv4 source-routed packets. Many networks drop these options, but some paths may still allow them. ## 4. Severity interpretation This behaves like an actionable Moderate issue rather than an Important memory-corruption vulnerability. The main impact is a capability-boundary bypass with possible protocol metadata exposure and limited routing-policy impact. The theoretical impact is bounded by network support for LSRR or SSRR. There is no evidence of kernel memory corruption, local privilege escalation, arbitrary write, kernel crash, or persistent host compromise. ## 5. One-sentence report phrase Unprivileged IPv4 sockets could set LSRR or SSRR source routing options without CAP_NET_RAW, allowing a local user to route packets through attacker controlled nodes and potentially expose TCP ISN or related protocol metadata when the network path accepts source routed packets. ## 6. Manual review recommendation MANUAL CHECK RECOMMENDED Manual review is recommended because this is a capability-boundary bypass in a core networking path and practical severity depends on deployment-specific filtering of IPv4 source-routing options. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: ipv4: restrict IPOPT_SSRR and IPOPT_LSRR options [ Upstream Commit: 4cd6e9ed49347d3a2fdaaf07e32fb524756dddc2 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=4cd6e9ed49347d3a2fdaaf07e32fb524756dddc2 Changed files: net/ipv4/ip_options.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=4cd6e9ed49347d3a2fdaaf07e32fb524756dddc2 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-53249 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53249 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:L/I:N/A:N The Best / paranoid CVSS vector: AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:N The Best / paranoid CVSS score: 4.4 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).