CVE-2026-74485

Received Received - Intake

Memory Corruption in Linux Kernel binfmt_misc

Publication date: 2026-08-15

Last updated on: 2026-08-19

Assigner: kernel.org

Description

In the Linux kernel, the following vulnerability has been resolved: binfmt_misc: reject a flag character as the field delimiter The registration string starts with a user chosen delimiter that separates the individual fields. So that the field parsers terminate even on a truncated string create_entry() pads the buffer with that same delimiter: memset(buf + count, del, 8); Most fields are scanned for the delimiter with strchr()/scanarg() and happily stop on the padding. The flags field is different: instead of scanning for the delimiter check_special_flags() consumes the flag characters 'P', 'O', 'C' and 'F' and stops at the first byte that is none of them, relying on the trailing delimiter to end the scan. If the delimiter is itself a flag character the padding no longer acts as a terminator. The scan swallows all eight padding bytes and keeps reading past the end of the allocation until it hits a byte that is not a flag character. For example registering PaPEPPxPPiP with 'P' as the delimiter (name "a", type extension, magic "x", interpreter "i", empty flags) leaves the flag scan running off the end of the buffer. The registration is rejected in the end because the parser does not stop exactly at buf + count, but only after the out of bounds read has already happened. With an unlucky allocation layout the scan can walk into an unmapped page; under KASAN it is reported as a slab out of bounds read. binfmt_misc mounts are available to unprivileged users in a user namespace so the read is reachable without privileges. Reject a delimiter that is one of the flag characters up front. Such a registration was always rejected anyway, only after the out of bounds read, so no valid registration string changes meaning.

CVSS Scores

EPSS Scores

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Meta Information

Published

2026-08-15

Last Modified

2026-08-19

Generated

2026-09-04

AI Q&A

2026-08-15

EPSS Evaluated

2026-09-03

NVD

CVE-2026-74485

EUVD

EUVD-2026-59678

Affected Vendors & Products

Vendor	Product	Version / Range
linux	linux_kernel	*

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-UNKNOWN

Attack-Flow Graph

Executive Summary

This vulnerability in the Linux kernel involves a flaw in the binfmt_misc module where a user-chosen delimiter character can cause an out-of-bounds memory read. The issue occurs when the delimiter is one of the flag characters ('P', 'O', 'C', 'F'), causing the parser to read past the allocated buffer into unmapped memory.

Detection Guidance

This vulnerability is specific to the Linux kernel's binfmt_misc module and requires local system access to detect. Check if binfmt_misc is mounted with: mount | grep binfmt_misc. If mounted, inspect the kernel version for affected releases. No direct network detection commands are applicable.

Impact Analysis

An attacker with access to a user namespace could exploit this to cause a denial of service or potentially escalate privileges by triggering a memory read outside the buffer. This could crash the system or lead to further exploitation if combined with other vulnerabilities.

Compliance Impact

This vulnerability does not directly affect compliance with GDPR, HIPAA, or similar standards. It is a low-level Linux kernel issue involving out-of-bounds memory reads during binfmt_misc registration, which could potentially lead to system instability or crashes but does not involve data exposure or processing violations that would impact regulatory compliance.

Mitigation Strategies

Update the Linux kernel to the latest patched version. If binfmt_misc is not required, unmount it with: sudo umount /proc/sys/fs/binfmt_misc/. Disable user namespace support if binfmt_misc is unused by setting kernel.unprivileged_userns_clone=0.

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