From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-68119][MODERATE REGULAR] tcp: initialize standalone TCP-AO response padding Date: Mon, 10 Aug 2026 18:10:21 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-68119 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: 4 X-AL-KERNEL-ActionableScore-Lower: unknown X-AL-KERNEL-Commit: bbb7db8c74b0b5d17a695136f0f0806ecd0118f6 List-Id: CVE: CVE-2026-68119 Priority: MODERATE REGULAR AL-KERNEL base severity: MODERATE KPANIC flag: NO Patch: tcp: initialize standalone TCP-AO response padding Commit: bbb7db8c74b0b5d17a695136f0f0806ecd0118f6 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=bbb7db8c74b0b5d17a695136f0f0806ecd0118f6 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68119 Analysis date: Mon, 10 Aug 2026 18:10:21 -0400 ActionableScore: 4 ActionableScore lower bound: unknown Actionable bucket: Borderline manual review recommended / below Important Manual review required: YES Summary: TCP-AO standalone TCP responses may transmit 1 to 3 bytes of uninitialized padding after the AO MAC to a reachable remote peer, causing a small kernel memory disclosure without evidence of integrity impact, availability impact, or privilege escalation. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-68119 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68119 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-2026-68119 MODERATE CHECK WITH IMPACT FROM ORIG NN IMPORTANT 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:N';CWE-908;*CWE-457;*CWE-200;Other CVSS 'AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N';BEST CVSS score: '5.9';DESCR 'TCP-AO standalone TCP responses can include uninitialized alignment padding after the AO MAC when the MAC length is not 4 byte aligned. These 1 to 3 padding bytes are part of the transmitted TCP header and may disclose small pieces of kernel memory from the response construction path to a remote peer. For the CVSS the PR:N is used because a remote attacker does not need a local account on the target, but reliable triggering requires access to a reachable TCP-AO protected endpoint and a configuration with an affected MAC length. The issue is network reachable in TCP-AO deployments, although TCP-AO is typically used in controlled routing or infrastructure networks rather than general public services. Impact is primarily confidentiality. No reliable integrity impact, availability impact, or privilege escalation primitive is visible from the patch context.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline manual review recommended / below Important (with actual score 4) SKIP CVE-2026-68119 UNKNOWN SKIP The Fixes patch not applied yet, so unlikely that actual: decde2586b34b99684faff1eab41e5c496c27fb6 YES NO NO unknown MAYBE REMOTE SIMPLEFIX NETWORK LINUS IPV6 LOWERED_FROM_HIGH_BASED_ON_GUESSCVSS DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5 - - checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=4 ## 1. ActionableScore * Conservative score: 4 * Paranoid score: 4 * Final recommended bucket: **Borderline manual review recommended / below Important** ## 2. Signal breakdown * Remote reachable / network-triggerable: +2 A remote peer that can reach a TCP-AO protected endpoint may receive standalone TCP responses containing the uninitialized padding bytes. * Confidentiality impact plausible: +1 The bug can disclose 1 to 3 bytes of uninitialized kernel stack or response-construction memory in transmitted TCP headers. * Common networking core path or packet-processing path: +1 The affected code is in TCP IPv4 and IPv6 response generation, though the vulnerable branch is limited to TCP-AO. * No generic memory corruption: +0 The patch only initializes padding before hashing and transmission. It does not show UAF, OOB write, double free, type confusion, arbitrary write, or lifetime corruption. * No integrity or availability signal: +0 No write primitive, privilege escalation path, crash, or persistent DoS is indicated. * No rare subsystem penalty applied: 0 TCP-AO is not commonly exposed like ordinary TCP services, but this is still a TCP networking path. The limited deployment is handled in reachability interpretation rather than subtracting score. ## 3. Reachability analysis The bug can be triggered only when TCP-AO is configured and a remote peer can interact with the protected TCP endpoint. No local account is required on the target, so the practical PR interpretation is PR:N for CVSS-style reasoning. However, TCP-AO is usually deployed in controlled routing, infrastructure, or private network environments rather than exposed broadly to the public Internet. Namespaces and containers do not materially improve attacker reachability unless they can access or influence a TCP-AO protected connection. Call-site confidence: high. The patch directly shows tcp_v4_send_ack() and tcp_v6_send_response() transmitting standalone TCP responses with TCP-AO options. ## 4. Severity interpretation This behaves like a network-reachable information disclosure, not memory corruption and not privilege escalation. The leak size is very small, only 1 to 3 padding bytes per affected response, and exploitation depends on TCP-AO configuration and MAC length alignment. Realistic impact is confidentiality-only and likely Moderate, but it should not be blindly auto-closed because the disclosure is remote and occurs in kernel networking code. ## 5. One-sentence report phrase TCP-AO standalone TCP responses may transmit 1 to 3 bytes of uninitialized padding after the AO MAC to a reachable remote peer, causing a small kernel memory disclosure without evidence of integrity impact, availability impact, or privilege escalation. ## 6. Manual review recommendation MANUAL CHECK REQUIRED Reason: this is a network-reachable kernel information disclosure, even though the leak is small and configuration-dependent. Manual review should confirm TCP-AO exposure, affected MAC lengths, and whether repeated responses can disclose security-relevant data in the evaluated product. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: tcp: initialize standalone TCP-AO response padding Commit: bbb7db8c74b0b5d17a695136f0f0806ecd0118f6 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=bbb7db8c74b0b5d17a695136f0f0806ecd0118f6 Commit description: tcp_v4_send_ack() and tcp_v6_send_response() construct standalone TCP responses with TCP-AO options. The option length carries the actual MAC length, but the TCP header length includes the option rounded up to a four-byte boundary. tcp_ao_hash_hdr() writes the MAC only. Thus, when the MAC length is not four-byte aligned, the one to three bytes after the MAC are left uninitialized and may be transmitted. For the normal TCP-AO hashing mode, those bytes also have to be initialized before computing the MAC. Initialize only the alignment padding in the TCP-AO branches, before hashing the header. Use TCPOPT_NOP, as in the normal TCP-AO output path. This avoids adding work to non-AO TCP responses while preserving a valid authenticated header. Fixes: decde25 ("net/tcp: Add TCP-AO sign to twsk") Fixes: da7dfaa ("net/tcp: Consistently align TCP-AO option in the header") Cc: stable@vger.kernel.org Reported-by: Yizhou Zhao Reported-by: Yuxiang Yang Reported-by: Ao Wang Reported-by: Xuewei Feng Reported-by: Qi Li Reported-by: Ke Xu Suggested-by: Eric Dumazet Signed-off-by: Yizhou Zhao Reviewed-by: Eric Dumazet Link: https://patch.msgid.link/20260713105631.8616-1-zhaoyz24@mails.tsinghua.edu.cn Signed-off-by: Jakub Kicinski Signed-off-by: Greg Kroah-Hartman Changed files: net/ipv4/tcp_ipv4.c net/ipv6/tcp_ipv6.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=bbb7db8c74b0b5d17a695136f0f0806ecd0118f6 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-68119 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-68119 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:N The Best / paranoid CVSS vector: AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N The Best / paranoid CVSS score: 5.9 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: 4 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).