From mboxrd@z Thu Jan 1 00:00:00 1970 From: AL-KERNEL To: kernel-cve@kernelcve.org Subject: [CVE-2026-53184][MODERATE 7.0] udp: clear skb->dev before running a sockmap verdict Date: Thu, 25 Jun 2026 17:30:06 -0400 Message-ID: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-AL-KERNEL-CVE: CVE-2026-53184 X-AL-KERNEL-Priority: MODERATE 7.0 X-AL-KERNEL-Severity: MODERATE 7.0 X-AL-KERNEL-Base-Severity: MODERATE X-AL-KERNEL-KPANIC: NO X-AL-KERNEL-ActionableScore: 5 X-AL-KERNEL-ActionableScore-Lower: 2 X-AL-KERNEL-Commit: 263779a6beff03b8b06f6d25566cb0f45af361f2 List-Id: CVE: CVE-2026-53184 Priority: MODERATE 7.0 AL-KERNEL base severity: MODERATE KPANIC flag: NO Patch: udp: clear skb->dev before running a sockmap verdict Commit: 263779a6beff03b8b06f6d25566cb0f45af361f2 Upstream patch: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=263779a6beff03b8b06f6d25566cb0f45af361f2 Original CVE announcement: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53184 Analysis date: Thu, 25 Jun 2026 17:30:06 -0400 ActionableScore: 5 ActionableScore lower bound: 2 Actionable bucket: Actionable Moderate at minimum Manual review required: YES Summary: A stale UDP `skb->dev` alias can be interpreted as a `struct net_device` pointer by BPF socket lookup helpers from a sockmap verdict path, causing a kernel crash, with practical triggering usually requiring local BPF/sockmap control rather than pure remote network access. ====================================================================== ABOUT THIS REPORT ====================================================================== The original Linux kernel CVE announcement for CVE-2026-53184 is available here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53184 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-2026-53184 MODERATE 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:L/I:L/A:H';CWE-704;CWE-843;**CWE-476;Other CVSS 'AV:L/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:H';BEST CVSS score: '5.8';DESCR 'A stale skb dev_scratch value can remain visible through skb dev on the UDP receive path before a sockmap verdict program runs. If the verdict program calls BPF socket lookup helpers, bpf_skc_lookup may treat that non pointer value as a struct net_device pointer and dereference it through dev_net, causing a general protection fault in softirq and a kernel crash. For the CVSS the PR:L paranoid value is used because a reduced capability local user, container root, or service account with BPF and sockmap control may be able to set up the vulnerable path without full host root. The issue is not a pure remote network vulnerability because the vulnerable path normally requires a local BPF sockmap configuration, although a received UDP packet can be the immediate trigger after that setup. Impact is at least local denial of service via kernel crash. Limited confidentiality or integrity impact is kept only in the paranoid score because the bug involves an invalid pointer dereference, but the patch context does not show an arbitrary write primitive.';YES REQUIRES MANUAL CHECK; ,and ActionableScore result is Actionable Moderate at minimum (with actual score 4) MAYBE REMOTE OOB BPF UAF NETWORK SKB HARDWARE LINUS IPV6 - - checked ====================================================================== ACTIONABLESCORE ANALYSIS ====================================================================== ActionableScore=5 ActionableScoreLower=2 ## 1. ActionableScore * Conservative score: **2** * Paranoid score: **5** * Final recommended bucket: **Actionable Moderate at minimum**:: ## 2. Signal breakdown ### Conservative score: 2 * **Weak/indirect corruption candidate: +1** `skb->dev` contains `dev_scratch`, not a valid `struct net_device *`, and is interpreted as an object pointer by `dev_net()`. This is pointer confusion / invalid struct interpretation, but no write primitive is shown. * **Reliable kernel crash / strong DoS: +1** The commit shows a general protection fault in softirq through `bpf_skc_lookup()`. * **Local unprivileged high-control kernel data-plane API: +1** The vulnerable path involves BPF sockmap / SK_SKB verdict programs, which provide high-control kernel data-plane behavior. * **Common networking core path or packet-processing path: +1** The crash happens in UDP receive processing after packet delivery into a sockmap-enabled socket. * **Requires admin/root/CAP_* in typical deployments: -2** Setting up BPF sockmap verdict programs typically requires privileged BPF and networking capabilities in normal host deployments. Total conservative: **2** ### Paranoid score: 5 * **Local unprivileged trigger: +1** In delegated environments, reduced-capability root, container root, or a service account with BPF/sockmap control may be able to set up the vulnerable path without full host-root equivalence. * **Weak/indirect corruption candidate: +1** The bug is not only a NULL dereference. It is an invalid interpretation of a non-pointer `dev_scratch` value as `struct net_device *`. * **Reliable kernel crash / strong DoS: +1** The observed failure is a kernel GPF in softirq, giving a strong local DoS outcome. * **Local high-control kernel data-plane API: +1** BPF sockmap and verdict programs increase attacker control over the call path once access is available. * **Common networking / packet-processing path: +1** A received UDP packet can be the immediate trigger after the sockmap/BPF setup. No strong UAF, arbitrary write, OOB write, refcount takeover, or page-cache corruption primitive is shown, so this should not be scored as an Important-class memory corruption issue by default. ## 3. Reachability analysis The bug is not a pure remote network vulnerability. A remote UDP packet can trigger the faulty path only after a local actor has configured a UDP socket in a sockmap and attached an SK_SKB verdict program that calls BPF socket lookup helpers. In typical deployments, this setup requires CAP_BPF, CAP_NET_ADMIN, or equivalent privileges, so the conservative privilege model is high. In containerized or delegated environments, the practical privilege requirement may be lower if a service account, container root, or reduced-capability user is allowed to manage BPF sockmaps. The affected code is in the networking receive path, but the vulnerable configuration is not default for ordinary UDP sockets. ## 4. Severity interpretation This behaves like an **Actionable Moderate** issue in the paranoid triage model. Realistically demonstrated impact is kernel crash / DoS. The patch supports an invalid pointer dereference caused by stale `skb->dev` aliasing, but it does not show attacker-controlled overwrite, reclaimable UAF, or a clear privilege escalation primitive. Theoretical concern is higher than a trivial NULL dereference because the bug combines networking, BPF sockmap, and bogus object-pointer interpretation in softirq context. That is enough to avoid auto-closing, but not enough to classify as a strong Important candidate without more evidence. ## 5. One-sentence report phrase A stale UDP `skb->dev` alias can be interpreted as a `struct net_device` pointer by BPF socket lookup helpers from a sockmap verdict path, causing a kernel crash, with practical triggering usually requiring local BPF/sockmap control rather than pure remote network access. ## 6. Manual review recommendation **MANUAL CHECK REQUIRED** Manual review is required because this combines BPF, sockmap, UDP receive processing, and invalid kernel object-pointer interpretation. The known impact is DoS, but delegated BPF/sockmap access and possible reduced-capability environments make it unsafe to auto-close as a low-risk crash-only issue. ====================================================================== UPSTREAM PATCH SUMMARY ====================================================================== Patch: udp: clear skb->dev before running a sockmap verdict Commit: 263779a6beff03b8b06f6d25566cb0f45af361f2 Upstream URL: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=263779a6beff03b8b06f6d25566cb0f45af361f2 Commit description: On the UDP receive path skb->dev is repurposed as dev_scratch (the truesize/state cache set by udp_set_dev_scratch()), through the union { struct net_device *dev; unsigned long dev_scratch; } in sk_buff. When a UDP socket is in a sockmap, sk_data_ready is sk_psock_verdict_data_ready(), which calls udp_read_skb() -> recv_actor() (sk_psock_verdict_recv) to run the attached SK_SKB verdict program in softirq. If that program calls a socket-lookup helper (bpf_sk_lookup_tcp/udp, bpf_skc_lookup_tcp), bpf_skc_lookup() does: if (skb->dev) caller_net = dev_net(skb->dev); skb->dev still holds the dev_scratch value (a non-NULL integer), so dev_net() dereferences it as a struct net_device * and the kernel takes a general protection fault on a non-canonical address in softirq: Oops: general protection fault, probably for non-canonical address 0x1010000800004a0 CPU: 1 UID: 0 PID: 1406 Comm: syz.2.19 Not tainted 7.1.0-rc6 #1 PREEMPT(full) RIP: 0010:bpf_skc_lookup net/core/filter.c:7033 [inline] RIP: 0010:bpf_sk_lookup+0x45/0x160 net/core/filter.c:7047 Call Trace: bpf_prog_4675cb904b7071f8+0x12e/0x14e bpf_prog_run_pin_on_cpu+0xc6/0x1f0 sk_psock_verdict_recv+0x1ba/0x350 udp_read_skb+0x31a/0x370 sk_psock_verdict_data_ready+0x2e3/0x600 __udp_enqueue_schedule_skb+0x4c8/0x650 udpv6_queue_rcv_one_skb+0x3ec/0x740 udp6_unicast_rcv_skb+0x11d/0x140 ip6_protocol_deliver_rcu+0x61e/0x950 ip6_input_finish+0xa9/0x150 NF_HOOK+0x286/0x2f0 ip6_input+0x117/0x220 NF_HOOK+0x286/0x2f0 __netif_receive_skb+0x85/0x200 process_backlog+0x374/0x9a0 __napi_poll+0x4f/0x1c0 net_rx_action+0x3b0/0x770 handle_softirqs+0x15a/0x460 do_softirq+0x57/0x80 The rmem charge that dev_scratch accounted for is released by skb_recv_udp() on dequeue, just above, so the scratch is dead by the time recv_actor() runs. Clear skb->dev so bpf_skc_lookup() falls back to sock_net(skb->sk), which skb_set_owner_sk_safe() set just above. Fixes: 965b57b ("net: Introduce a new proto_ops ->read_skb()") Cc: stable@vger.kernel.org Signed-off-by: Sechang Lim Reviewed-by: Jiayuan Chen Reviewed-by: Eric Dumazet Link: https://patch.msgid.link/20260603162737.697215-1-rhkrqnwk98@gmail.com Signed-off-by: Jakub Kicinski Signed-off-by: Greg Kroah-Hartman Changed files: net/core/filter.c net/ipv4/udp.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=263779a6beff03b8b06f6d25566cb0f45af361f2 ====================================================================== DETAILED REPORT METHODOLOGY ====================================================================== The original Linux kernel CVE announcement for CVE-2026-53184 can be found here: https://lore.kernel.org/linux-cve-announce/?q=CVE-2026-53184 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:N/I:N/A:H The Best / paranoid CVSS vector: AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:H The Best / paranoid CVSS score: 5.8 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: 2 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: NO 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).