binfmt_misc: reject a flag character as the field delimiter

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-74485
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-08-15 13:17:53 UTC
Updated2026-08-19 17:21:05 UTC
DescriptionIn 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.

Risk And Classification

Primary CVSS: v3.1 7.1 HIGH from 416baaa9-dc9f-4396-8d5f-8c081fb06d67

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H

EPSS: 0.001250000 probability, percentile 0.026400000 (date 2026-08-19)

VersionSourceTypeScoreSeverityVector
3.1416baaa9-dc9f-4396-8d5f-8c081fb06d67Secondary7.1HIGHCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H
3.1CNADECLARED7.1HIGHCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H

CVSS v3.1 Breakdown

Attack Vector
Local
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
None
Availability
High

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:H

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 96bd5d4fea2970b9b08265293ca7a10b9b27c0fd git Not specified
CNA Linux Linux affected 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 9970e094e5d60f0d66914bf9a97d1ef19107ebf5 git Not specified
CNA Linux Linux affected 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 b29e3c1f375c1296362d219ff38bceddf2d2a88a git Not specified
CNA Linux Linux affected 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 1819f82dee766c58295ecaacdac02cdf6837d7a4 git Not specified
CNA Linux Linux affected 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 1853e95c9bfe69ef1dd862b3f551e68f4a1b76cc git Not specified
CNA Linux Linux affected 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 840bb9c49c3e75fb32b593d67ab32f6b77122262 git Not specified
CNA Linux Linux affected 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 9a2d87db3898b5993b64fd258d0334e0eba9ee0d git Not specified
CNA Linux Linux affected 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 8e85d50ba1117fd446bf9a250bd8a97d48384bdc git Not specified
CNA Linux Linux affected 2.6.12 Not specified
CNA Linux Linux unaffected 2.6.12 semver Not specified
CNA Linux Linux unaffected 5.10.265 5.10.* semver Not specified
CNA Linux Linux unaffected 5.15.216 5.15.* semver Not specified
CNA Linux Linux unaffected 6.1.183 6.1.* semver Not specified
CNA Linux Linux unaffected 6.6.151 6.6.* semver Not specified
CNA Linux Linux unaffected 6.12.103 6.12.* semver Not specified
CNA Linux Linux unaffected 6.18.44 6.18.* semver Not specified
CNA Linux Linux unaffected 7.1.8 7.1.* semver Not specified
CNA Linux Linux unaffected 7.2 * original_commit_for_fix Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/840bb9c49c3e75fb32b593d67ab32f6b77122262 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/8e85d50ba1117fd446bf9a250bd8a97d48384bdc 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/9970e094e5d60f0d66914bf9a97d1ef19107ebf5 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/b29e3c1f375c1296362d219ff38bceddf2d2a88a 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/96bd5d4fea2970b9b08265293ca7a10b9b27c0fd 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/1853e95c9bfe69ef1dd862b3f551e68f4a1b76cc 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/9a2d87db3898b5993b64fd258d0334e0eba9ee0d 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
git.kernel.org/stable/c/1819f82dee766c58295ecaacdac02cdf6837d7a4 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org
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