# CVE-2026-68386: bpf, sockmap: Reject unhashed UDP sockets on sockmap update

Status: published. Published: 2026-08-10. Updated: 2026-11-06.

In the Linux kernel, the following vulnerability has been resolved:

bpf, sockmap: Reject unhashed UDP sockets on sockmap update

UDP sockets get SOCK_RCU_FREE set when (auto-)bound. This means
sk_is_refcounted(unbound) = true, while sk_is_refcounted(bound) = false.

Because sockmap accepts unbound UDP sockets, a BPF program can increment a
socket's refcount via lookup. If the socket is subsequently bound, the
transition from unbound to bound causes bpf_sk_release() to skip the
decrement of the refcount, causing a memory leak.

unreferenced object 0xffff88810bc2eb40 (size 1984):
  comm "test_progs", pid 2451, jiffies 4295320596
  hex dump (first 32 bytes):
    7f 00 00 01 7f 00 00 01 d2 04 1b b7 04 d2 00 00  ................
    02 00 01 40 00 00 00 00 00 00 00 00 00 00 00 00  ...@............
  backtrace (crc bdee079d):
    kmem_cache_alloc_noprof+0x557/0x660
    sk_prot_alloc+0x69/0x240
    sk_alloc+0x30/0x460
    inet_create+0x2ce/0xf80
    __sock_create+0x25b/0x5c0
    __sys_socket+0x119/0x1d0
    __x64_sys_socket+0x72/0xd0
    do_syscall_64+0xa1/0x5f0
    entry_SYSCALL_64_after_hwframe+0x76/0x7e

Instead of special-casing for refcounted sockets, reject unhashed UDP
sockets during sockmap updates, as there is no benefit to supporting those.
This effectively reverts the commit under Fixes, with two exceptions:

1. sock_map_sk_state_allowed() maintains a fall-through `return true`.
2. In the spirit of commit b8b8315e39ff ("bpf, sockmap: Remove unhash
   handler for BPF sockmap usage"), the proto::unhash BPF handler is not
   reintroduced.

Historical note: this issue is related to commit 67312adc96b5 ("bpf: reject
unhashed sockets in bpf_sk_assign").

## Remediation

No remediation reported in collected sources

## Affected products and versions

- Linux / Linux: ≥ 0c48eefae712c2fd91480346a07a1a9cd0f9470b; < 2271276ac5279d2d204be7739a1a28d4ef6cf608 (affected, git); ≥ 0c48eefae712c2fd91480346a07a1a9cd0f9470b; < 7ffe529e7127411806c8692fb1490f552c629dc2 (affected, git); ≥ 0c48eefae712c2fd91480346a07a1a9cd0f9470b; < 17b7ef6b86112a4e61cee1e9009a4b318e3225c5 (affected, git); ≥ 0c48eefae712c2fd91480346a07a1a9cd0f9470b; < 250474c69bc3fc48a5fc21d7c349f279caad947a (affected, git); ≥ 0c48eefae712c2fd91480346a07a1a9cd0f9470b; < 8692655da369961128658cf8539334b6a960ecb0 (affected, git); ≥ 0c48eefae712c2fd91480346a07a1a9cd0f9470b; < 66efd3368ae10d05e08fbe6425b50fdec7186ac7 (affected, git). Source: CNA: Linux
- Linux / Linux: 5.15 (affected); ≥ 0; < 5.15 (unaffected, semver); ≥ 6.1.183; ≤ 6.1.* (unaffected, semver); ≥ 6.6.148; ≤ 6.6.* (unaffected, semver); ≥ 6.12.101; ≤ 6.12.* (unaffected, semver); ≥ 6.18.42; ≤ 6.18.* (unaffected, semver); ≥ 7.1.6; ≤ 7.1.* (unaffected, semver); ≥ 7.2; ≤ * (unaffected, original_commit_for_fix). Source: CNA: Linux

## Severity and prioritization

- CISA KEV: No listing in collected sources

- EPSS: 0.21% as of 2026-11-06; percentile 11.44%

- SSVC: exploitation none; automatable no; technical impact partial; source ADP: CISA-ADP

- Weaknesses: Not reported

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://git.kernel.org/stable/c/2271276ac5279d2d204be7739a1a28d4ef6cf608 (CNA: Linux)

- https://git.kernel.org/stable/c/7ffe529e7127411806c8692fb1490f552c629dc2 (CNA: Linux)

- https://git.kernel.org/stable/c/17b7ef6b86112a4e61cee1e9009a4b318e3225c5 (CNA: Linux)

- https://git.kernel.org/stable/c/250474c69bc3fc48a5fc21d7c349f279caad947a (CNA: Linux)

- https://git.kernel.org/stable/c/8692655da369961128658cf8539334b6a960ecb0 (CNA: Linux)

- https://git.kernel.org/stable/c/66efd3368ae10d05e08fbe6425b50fdec7186ac7 (CNA: Linux)

- https://git.kernel.org/stable/c/17b7ef6b86112a4e61cee1e9009a4b318e3225c5 (416baaa9-dc9f-4396-8d5f-8c081fb06d67)

- https://git.kernel.org/stable/c/2271276ac5279d2d204be7739a1a28d4ef6cf608 (416baaa9-dc9f-4396-8d5f-8c081fb06d67)

- https://git.kernel.org/stable/c/250474c69bc3fc48a5fc21d7c349f279caad947a (416baaa9-dc9f-4396-8d5f-8c081fb06d67)

- https://git.kernel.org/stable/c/66efd3368ae10d05e08fbe6425b50fdec7186ac7 (416baaa9-dc9f-4396-8d5f-8c081fb06d67)

- https://git.kernel.org/stable/c/7ffe529e7127411806c8692fb1490f552c629dc2 (416baaa9-dc9f-4396-8d5f-8c081fb06d67)

- https://git.kernel.org/stable/c/8692655da369961128658cf8539334b6a960ecb0 (416baaa9-dc9f-4396-8d5f-8c081fb06d67)

## Provenance

- CNA: Linux: https://www.cve.org/CVERecord?id=CVE-2026-68386; retrieved 2026-11-06; source updated 2026-11-06

- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-68386; retrieved 2026-11-06; source updated 2026-11-06

- FIRST EPSS: https://api.first.org/data/v1/epss?cve=CVE-2026-68386; retrieved 2026-11-06; source updated Not reported

Revision: 4436a18b711329defcf97b89c8fbb060cb9e623343c0935bb8a187be6b3852e5

Canonical: https://y2.dev/cve/CVE-2026-68386

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