From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-64411][MODERATE REGULAR] netfilter: ebtables: terminate table name before find_table_lock() Date: Sat, 25 Jul 2026 11:19:17 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-64411 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: 1 X-AL-KERNEL-Commit: 4c046ca4e35a83ea32f6e748f54139f5fe2a1d01 List-Id: CVE: CVE-2026-64411 Priority: MODERATE REGULAR AL-KERNEL base severity: MODERATE KPANIC flag: NO Patch: netfilter: ebtables: terminate table name before find_table_lock() Commit: 4c046ca4e35a83ea32f6e748f54139f5fe2a1d01 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=4c046ca4e35a83ea32f6e748f54139f5fe2a1d01 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64411 Analysis date: Sat, 25 Jul 2026 11:19:17 -0400 ActionableScore: 3 ActionableScore lower bound: 1 Actionable bucket: Borderline, manual review recommended Manual review required: YES Summary: An unterminated ebtables table name can cause `request_module()` formatting to read past a stack buffer on a lookup miss, creating a local kernel stack out-of-bounds read with possible information disclosure, typically requiring CAP_NET_ADMIN but potentially reachable from delegated network namespaces. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-64411 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64411 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-2026-64411 MODERATE CHECK WITH IMPACT FROM ORIG NN MODERATE 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:L';CWE-170;CWE-126;*CWE-200;Other CVSS 'AV:L/AC:L/PR:H/UI:N/S:U/C:L/I:N/A:L';BEST CVSS score: '6.1';DESCR 'An unterminated ebtables table name can reach find_table_lock() and then request_module formatting on a lookup miss, causing vsnprintf() to read past the 32 byte name field into adjacent stack data. This is a local control plane issue through ebtables setsockopt handling, not a packet based network trigger. For the CVSS the PR:L value is used for the paranoid score because local attackers may reach the path through CAP_NET_ADMIN in a user namespace or delegated container context, even though many base systems require administrative firewall control. Impact is at least a local kernel stack out-of-bounds read. In the worst defensible case it may disclose kernel stack data through the generated module request name and may crash KASAN or hardened kernels. No write primitive is shown, so integrity impact is not assigned.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Borderline, manual review recommended (with actual score 2) YES READ KASAN OOB NETFILTER LINUS INCREASED_TO_MODERATE7_FROM_MODERATE_BASED_ON_GUESSCVSS DECREASED_TO_MODERATEREG_BASED_ON_ACTIONABLESCORELESSTHAN5 NO NO checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=3 ActionableScoreLower=1 ## 1. ActionableScore * Conservative score: 1 * Paranoid score: 3 * Final recommended bucket: **Borderline, manual review recommended**:: ## 2. Signal breakdown Conservative signals: * Confidentiality impact plausible: +1. The bug is a stack out-of-bounds read in `vsnprintf()` and may read adjacent kernel stack bytes into the generated module request string. * Broad/common subsystem exposure: +1. ebtables/netfilter code is widely available, although this is a control-plane path, not a packet-processing path. * Requires CAP_NET_ADMIN in typical deployments: -1. The affected setsockopt path normally requires firewall administration capability, but CAP_NET_ADMIN is not always equivalent to full host root in containerized or delegated environments. Conservative total: 1. Paranoid additional interpretation: * Local unprivileged trigger: +1. In systems with unprivileged user namespaces or delegated network namespaces, a local user may obtain effective CAP_NET_ADMIN for this path. * Confidentiality impact plausible: +1. The unterminated string can over-read stack contents before hitting a NUL byte. * Broad/common subsystem exposure: +1. netfilter/ebtables is common enough to avoid treating this as rare-only exposure. Paranoid total: 3. Not counted: * No generic memory corruption score. This is read-only stack OOB, not UAF, double free, OOB write, type confusion, or arbitrary write. * No privilege escalation score. The patch does not show reclaim, overwrite, callback control, refcount abuse, or a write primitive. * No strong DoS score. The KASAN report demonstrates the bug, but production impact is more likely limited over-read or possible hardened-kernel failure rather than a reliably demonstrated system-wide crash. ## 3. Reachability analysis The trigger is local through ebtables/netfilter control-plane setsockopt handling. It is not remotely reachable through packet traffic. In standard host deployments, the caller typically needs CAP_NET_ADMIN or equivalent firewall-management privileges. In containerized systems or systems with unprivileged user namespaces, the effective privilege requirement may be lower if an attacker can create or control a network namespace with ebtables access. The affected path is old and broadly present, but exploitation depends on being able to issue the relevant ebtables update operation and force a lookup miss that reaches `request_module()` formatting. Call-site confidence: high. The commit message provides the direct call trace from `update_counters()` through `find_table_lock()`, `try_then_request_module()`, and `vsnprintf()`. ## 4. Severity interpretation This behaves like a borderline actionable Moderate rather than an Important-class kernel vulnerability. The concrete primitive is a stack out-of-bounds read caused by missing NUL termination of a user-supplied table name. The realistic impact is possible kernel stack information disclosure through the module request formatting path, with possible crash only in KASAN or hardened configurations. There is no demonstrated write primitive, memory lifetime corruption, object replacement, or practical LPE chain. ## 5. One-sentence report phrase An unterminated ebtables table name can cause `request_module()` formatting to read past a stack buffer on a lookup miss, creating a local kernel stack out-of-bounds read with possible information disclosure, typically requiring CAP_NET_ADMIN but potentially reachable from delegated network namespaces. ## 6. Manual review recommendation MANUAL CHECK RECOMMENDED. This should not be auto-closed solely as a low-risk correctness fix because it has a concrete stack OOB read primitive and a plausible information-disclosure path, but it does not currently justify Important-class handling without evidence of reliable disclosure, write corruption, or LPE. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: netfilter: ebtables: terminate table name before find_table_lock() Commit: 4c046ca4e35a83ea32f6e748f54139f5fe2a1d01 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=4c046ca4e35a83ea32f6e748f54139f5fe2a1d01 Commit description: update_counters() and compat_update_counters() forward a user-supplied 32-byte table name to find_table_lock() without NUL-terminating it. On a lookup miss, find_inlist_lock() calls try_then_request_module(..., "%s%s", "ebtable_", name), and vsnprintf() reads past the name field and the stack object until it hits a zero byte. BUG: KASAN: stack-out-of-bounds in string (lib/vsprintf.c:648 lib/vsprintf.c:730) Read of size 1 at addr ffff8880119dfb20 by task exploit/147 Call Trace: ... string (lib/vsprintf.c:648 lib/vsprintf.c:730) vsnprintf (lib/vsprintf.c:2945) __request_module (kernel/module/kmod.c:150) do_update_counters.isra.0 (net/bridge/netfilter/ebtables.c:371 net/bridge/netfilter/ebtables.c:380) update_counters (net/bridge/netfilter/ebtables.c:1440) do_ebt_set_ctl (net/bridge/netfilter/ebtables.c:2573) nf_setsockopt (net/netfilter/nf_sockopt.c:101) ip_setsockopt (net/ipv4/ip_sockglue.c:1424) raw_setsockopt (net/ipv4/raw.c:847) __sys_setsockopt (net/socket.c:2393) ... compat_do_replace() shares the same unterminated name via compat_copy_ebt_replace_from_user(); terminate it there too so all find_table_lock() callers behave alike. The other callers already terminate the name after the copy. Fixes: 1da177e ("Linux-2.6.12-rc2") Fixes: 81e675c ("netfilter: ebtables: add CONFIG_COMPAT support") Cc: stable@vger.kernel.org Reported-by: Weiming Shi Assisted-by: Claude:claude-opus-4-8 Signed-off-by: Xiang Mei Signed-off-by: Florian Westphal Signed-off-by: Greg Kroah-Hartman Changed files: lib/vsprintf.c kernel/module/kmod.c net/bridge/netfilter/ebtables.c net/netfilter/nf_sockopt.c net/ipv4/ip_sockglue.c net/ipv4/raw.c net/socket.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=4c046ca4e35a83ea32f6e748f54139f5fe2a1d01 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-64411 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-64411 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:H/UI:N/S:U/C:L/I:N/A:L The Best / paranoid CVSS vector: AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:L The Best / paranoid CVSS score: 6.1 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: 1 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).