CVE-2026-74689

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

Published Aug 22, 2026 CVSS 3.1 · 7.1 High EPSS < 1% KEV · Not listed
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.

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

Source ID Title
Debian DLA Debian DLA DLA-4777-1 linux security update
Debian DLA Debian DLA DLA-4788-1 linux-6.12 security update
Debian DSA Debian DSA DSA-6466-1 linux security update
Ubuntu USN Ubuntu USN USN-9019-1 Linux kernel (Azure) vulnerabilities
Ubuntu USN Ubuntu USN USN-9020-1 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-9022-1 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-9023-1 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-9024-1 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-9025-1 Linux kernel vulnerabilities
Ubuntu USN Ubuntu USN USN-9026-1 Linux kernel (Azure) vulnerabilities
Ubuntu USN Ubuntu USN USN-9039-1 Linux kernel (Azure CVM) vulnerabilities
Ubuntu USN Ubuntu USN USN-9040-1 Linux kernel (Low Latency NVIDIA) vulnerabilities
Ubuntu USN Ubuntu USN USN-9066-1 Linux kernel (HWE) vulnerabilities
History
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Type Values Removed Values Added
Weaknesses CWE-120
CWE-200
Type Values Removed Values Added
Metrics cvssV3_1

{'score': 7.1, 'vector': 'CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H'}

Type Values Removed Values Added
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.
Title net/atm: fix slab-out-of-bounds read in vcc_setsockopt()
First Time appeared Linux
Linux linux Kernel
CPEs cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*
Vendors & Products Linux
Linux linux Kernel
References
Weaknesses

Sources

Status
PUBLISHED
Assigner
Linux
Published
Updated
Oct 16, 2026, 7:16 PM
Reserved
Aug 15, 2026, 5:44 AM
Status
Received
Published
Aug 22, 2026, 4:16 PM
Modified
Oct 16, 2026, 8:17 PM
Severity
Moderate
Public date
Aug 22, 2026, 12:00 AM