CVE-2026-74689: net/atm: fix slab-out-of-bounds read in vcc_setsockopt()

Severity: high (CVSS 7.1 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.1% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-08-22 · updated 2026-10-16

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.

Affected products

Linux kernel: 2.6.12 — fixed in 7.2

How to fix

Upgrade to a fixed version: Linux kernel 7.2. Check the vendor advisory for mitigations.

References

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