EUVD-2026-64526
GHSA-h943-r25q-4c77
Severity by source
AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Race condition requires precise concurrent timing (AC:H); accessing the vulnerable code path requires local socket access to a BPF sockmap-enrolled socket (PR:L, not PR:N as NVD assigned).
Primary rating from Vendor (Linux).
CVSS VectorVendor: Linux
CVSS:3.1/AV:L/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Lifecycle Timeline
5DescriptionCVE.org
In the Linux kernel, the following vulnerability has been resolved:
bpf, sockmap: Fix sk_redir use-after-free in send verdict
sk_psock_msg_verdict() takes a socket reference for psock->sk_redir. tcp_bpf_send_verdict() copies that pointer while holding the source socket lock, but does not take a reference for the local copy before dropping the lock around tcp_bpf_sendmsg_redir().
When apply_bytes keeps the cached verdict active, another sendmsg() on the same source socket can consume the remaining bytes and release the cached reference while the first thread still holds only the raw local pointer:
CPU 0 CPU 1 sk_redir = psock->sk_redir apply_bytes remains nonzero release_sock(sk) lock_sock(sk) apply_bytes reaches zero psock->sk_redir = NULL release_sock(sk) tcp_bpf_sendmsg_redir(sk_redir) sock_put(sk_redir) tcp_bpf_sendmsg_redir(sk_redir)
The final sock_put() can free sk_redir before CPU 0 dereferences it.
KASAN reported:
BUG: KASAN: slab-use-after-free in tcp_bpf_sendmsg_redir+0xf39/0x1020 Read of size 8 at addr ffff888108537090 by task poc/87 Call Trace: tcp_bpf_sendmsg_redir+0xf39/0x1020 tcp_bpf_sendmsg+0x977/0x1a50 __sys_sendto+0x32c/0x3a0 __x64_sys_sendto+0xdb/0x1b0 Allocated by task 85: sk_prot_alloc+0x56/0x210 sk_clone+0x6f/0x14b0 inet_csk_clone_lock+0x24/0x740 tcp_create_openreq_child+0x25/0x2710 tcp_v4_syn_recv_sock+0x10a/0xe00 Freed by task 0: __kasan_slab_free+0x43/0x70 slab_free_after_rcu_debug+0xa6/0x1e0 rcu_core+0x50a/0x1850 Last potentially related work creation: __sk_destruct+0x3da/0x540 sk_psock_destroy+0x81e/0xab0 process_one_work+0x63a/0x1070
Take a temporary socket reference while the source socket lock still protects psock->sk_redir, and drop it after tcp_bpf_sendmsg_redir() returns. This keeps each unlocked use independent of cached-verdict ownership.
AnalysisAI
Use-after-free race condition in the Linux kernel BPF sockmap subsystem allows a local attacker with access to a sockmap-configured TCP socket to corrupt kernel memory, with high impact on confidentiality, integrity, and availability. The flaw exists in tcp_bpf_send_verdict(), where a local pointer copy of psock->sk_redir is made without incrementing the socket reference count before the source socket lock is released, enabling a concurrent sendmsg() thread to free the socket object while the first thread still holds the stale raw pointer. …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | Exploitation requires all of the following: (1) a TCP socket enrolled in a BPF sockmap with an active sk_redir verdict - meaning a BPF program using bpf_msg_redirect_map() or equivalent must already be loaded and attached, which on most distributions requires CAP_BPF or CAP_NET_ADMIN; (2) the psock apply_bytes counter must be nonzero, meaning the verdict was cached across multiple sendmsg() operations rather than evaluated per-message; (3) two concurrent sendmsg() callers on the same source socket must race to consume the apply_bytes budget - a timing-dependent condition. … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | The NVD CVSS score of 8.4 with AV:L/AC:L/PR:N/UI:N and full C:H/I:H/A:H suggests a highly impactful local vulnerability, but several signals moderate the realistic exploitation priority. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | A local process with access to a TCP socket enrolled in a BPF sockmap verdict program (e.g., within a container environment running Cilium) spawns two threads that simultaneously invoke sendmsg() on the same source socket with apply_bytes set to a value that spans multiple send calls. Thread B exhausts apply_bytes first, causing the kernel to set psock->sk_redir to NULL and call sock_put() on the redirect target socket, freeing it. … |
| Remediation | Upgrade to a patched Linux kernel stable release: 5.10.265, 5.15.216, 6.1.183, 6.6.152, 6.12.104, 6.18.45, 7.1.9, or the 7.2 series. … Detailed patch versions, workarounds, and compensating controls in full report. |
Recommended ActionAI
Within 24 hours, inventory all Linux systems in scope, mapping kernel versions and identifying active BPF sockmap configurations, particularly in container orchestration and edge infrastructure layers. …
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