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CVE-2026-74485

binfmt_misc: reject a flag character as the field delimiter

Published
Last modified
published
Not listed in CISA KEV
Fix
Fixed in 5.10.265, 5.15.216, 6.1.183, 6.6.151, 6.12.103, and 2 more
None on Exploit-DB, Metasploit or GitHub
  • Exploitation: none
  • Automatable: no
  • Technical impact: partial

Summary

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.

Timeline

  1. CVE published
  2. CISA SSVC assessment

    Exploitation: none · Automatable: no · Technical impact: partial

  3. Record last updated

Affected versions

  • Linux Linux

    From 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 · fixed in 96bd5d4fea2970b9b08265293ca7a10b9b27c0fd; From 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 · fixed in 9970e094e5d60f0d66914bf9a97d1ef19107ebf5; From 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 · fixed in b29e3c1f375c1296362d219ff38bceddf2d2a88a; From 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 · fixed in 1819f82dee766c58295ecaacdac02cdf6837d7a4; From 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 · fixed in 1853e95c9bfe69ef1dd862b3f551e68f4a1b76cc; From 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 · fixed in 840bb9c49c3e75fb32b593d67ab32f6b77122262; From 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 · fixed in 9a2d87db3898b5993b64fd258d0334e0eba9ee0d; From 1da177e4c3f41524e886b7f1b8a0c1fc7321cac2 · fixed in 8e85d50ba1117fd446bf9a250bd8a97d48384bdc

  • Linux Linux

    2.6.12

  • KernelLinux

    From 2.6.12 · fixed in 5.10.265; From 5.11.0 · fixed in 5.15.216; From 5.16.0 · fixed in 6.1.183; From 6.2.0 · fixed in 6.6.151; From 6.7.0 · fixed in 6.12.103; From 6.13.0 · fixed in 6.18.44; From 6.19.0 · fixed in 7.1.8

References 8

git.kernel.org