From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-52935][MODERATE 7.0] xfrm: espintcp: do not reuse an in-progress partial send Date: Wed, 24 Jun 2026 04:34:23 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-52935 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: 6564e9c7af7e1dc7bfe7f3093b728abe484d7630 List-Id: CVE: CVE-2026-52935 Priority: MODERATE 7.0 AL-KERNEL base severity: MODERATE KPANIC flag: YES Patch: xfrm: espintcp: do not reuse an in-progress partial send Commit: 6564e9c7af7e1dc7bfe7f3093b728abe484d7630 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=6564e9c7af7e1dc7bfe7f3093b728abe484d7630 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-52935 Analysis date: Wed, 24 Jun 2026 04:34:23 -0400 ActionableScore: 5 ActionableScore lower bound: 4 Actionable bucket: Actionable Moderate at minimum Manual review required: YES Summary: An XFRM ESP-in-TCP partial-send state bug can reuse a live ctx partial object with a stale offset, causing an out-of-bounds read in the send path and potentially allowing remote DoS or limited data exposure in configured ESP-in-TCP deployments. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-52935 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-52935 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-2026-52935 MODERATE CHECK Maybe valid. Check manually. Hints by AL-KERNEL: The best (paranoid) CVSS is 'AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:H';CWE-125;CWE-362;*CWE-664;Other CVSS 'AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:H';BEST CVSS score: '7.4';DESCR 'xfrm espintcp can reuse ctx partial while a previous partial send is still in progress. This can attach a stale offset to a new sk_msg and lead to an out of bounds read in the send path. For the CVSS the PR:N is used because a network peer does not need local privileges on the target system, although the target must use ESP in TCP and the attacker must be able to influence a configured transport path. The issue is network reachable in affected IPsec ESP in TCP deployments, but exploitation is high complexity because it depends on an in progress partial send and timing or backpressure conditions. Impact is at least denial of service via kernel crash and may include confidentiality impact if out of bounds data is copied into the transmit path. Integrity impact is not assumed because the patch supports an out of bounds read primitive, not an out of bounds write or arbitrary write primitive.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate at minimum (with actual score 5) YES REMOTE LOCK NETWORK LINUS KPANIC 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: * Remote reachable / network-triggerable: +2 Applies for systems using XFRM ESP-in-TCP where a peer can influence the transport path and partial-send conditions. * Memory corruption, weak or indirect corruption candidate: +1 The commit explicitly describes a memory-safety issue where stale partial-send state can lead to an out-of-bounds read. This is not an OOB write or UAF reclaim primitive. * Reliable kernel crash / strong DoS: +1 An OOB read in the kernel send path can plausibly cause an Oops or crash. * Confidentiality impact plausible: +1 Because the OOB read occurs in a send path, there is a plausible risk that unintended kernel-adjacent data could be copied into transmitted output, but this is not proven. * Hard or timing-dependent condition: -1 The trigger depends on an in-progress partial send, blocking behavior, and backpressure or timing conditions. Conservative total: 4 Paranoid adjustment: * Do not subtract the timing penalty in the paranoid score: +1 relative to conservative If TCP backpressure and repeated sends are naturally reachable in a real ESP-in-TCP deployment, the race-like partial-send condition may be reproducible enough to avoid the -1 reliability penalty. Paranoid total: 5 Not counted: * No privilege escalation bonus. The patch supports OOB read and DoS, not a write primitive, object replacement, callback control, refcount takeover, or type confusion. * No integrity impact. The described primitive is read-only. * No Dirty-Pipe-like bonus. This is not page-cache or COW ownership corruption. ## 3. Reachability analysis A remote peer can plausibly influence this path only when ESP-in-TCP is configured and the attacker can interact with the affected IPsec transport. This is not a default Internet-wide exposure, but XFRM/IPsec should not be treated as an obscure local-only subsystem. The most realistic trigger requires a configured ESP-in-TCP connection plus conditions that leave a previous partial send in progress while a new send is attempted. Local namespaces do not materially reduce the main remote interpretation. Local configuration of XFRM normally requires elevated privileges such as CAP_NET_ADMIN, but the relevant attacker model here is a peer influencing an already configured transport path. ## 4. Severity interpretation This is stronger than an ordinary Moderate because the patch explicitly fixes a memory-safety bug in a network send path and names an out-of-bounds read. It is not a Strong Important candidate by itself because the primitive is read-only, timing-dependent, and does not show attacker-controlled overwrite, UAF reclaim, type confusion, or privilege escalation. The realistic impact is DoS, with plausible confidentiality concern if OOB data can be transmitted. The theoretical worst case justifies manual review, but not an automatic Important classification. ## 5. One-sentence report phrase An XFRM ESP-in-TCP partial-send state bug can reuse a live ctx partial object with a stale offset, causing an out-of-bounds read in the send path and potentially allowing remote DoS or limited data exposure in configured ESP-in-TCP deployments. ## 6. Manual review recommendation MANUAL CHECK REQUIRED Reason: this is a network-reachable memory-safety issue with an explicit out-of-bounds read in the send path. Even though exploitation appears timing-dependent and no write or LPE primitive is shown, the confidentiality and crash implications are sufficient to avoid auto-closure. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: xfrm: espintcp: do not reuse an in-progress partial send Commit: 6564e9c7af7e1dc7bfe7f3093b728abe484d7630 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=6564e9c7af7e1dc7bfe7f3093b728abe484d7630 Commit description: espintcp keeps a single in-flight transmit in ctx->partial. Before building a new sk_msg, espintcp_sendmsg() first tries to flush that state through espintcp_push_msgs(). For blocking callers, espintcp_push_msgs() may return success even when the previous partial send is still pending. espintcp_sendmsg() would then reinitialize emsg->skmsg and reuse ctx->partial while the old transfer still owns that state. Do not rebuild the send message when ctx->partial is still in progress. If espintcp_push_msgs() returns with emsg->len still set, fail the new send instead of overwriting the live partial state. This is a memory-safety fix: reusing the live partial-send state can leave a stale offset attached to a new sk_msg and lead to an out-of- bounds read in the send path. tcp_sendmsg_locked() already handles waiting for send buffer memory, so the fix here is just to preserve espintcp's one-message-at-a-time transmit state. Fixes: e27cca9 ("xfrm: add espintcp (RFC 8229)") Cc: stable@kernel.org Reported-by: Yuan Tan Reported-by: Yifan Wu Reported-by: Juefei Pu Reported-by: Zhengchuan Liang Reported-by: Xin Liu Assisted-by: Codex:GPT-5.4 Signed-off-by: Wyatt Feng Signed-off-by: Ren Wei Signed-off-by: Steffen Klassert Signed-off-by: Greg Kroah-Hartman Changed files: net/xfrm/espintcp.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=6564e9c7af7e1dc7bfe7f3093b728abe484d7630 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-52935 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-52935 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:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:H The Best / paranoid CVSS vector: AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:H The Best / paranoid CVSS score: 7.4 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).