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CVE-2026-18374VulnerabilityPublished Updated

Eglibc: Passing an effectively empty string to the ,ccs= syntax extension of the mode argument in the fopen function

Affects eglibcSource GCVE Database

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Authoritative record:CVE-2026-18374· Medium 4.9

Not known to be exploited · CVSS 4.9 Medium.

Data as of 9 Nov 2026, 14:21 UTC

CVSS 3.1 base score
4.9Medium
How severe the flaw is on the 0–10 CVSS scale.
CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:L

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 27 Aug 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 9 Nov 2026.

What to do

Affected software

ProductAffectedFixed in
Ubuntu Pro 20.04 LTSglibcpkg:deb/ubuntu/glibc?arch=source&distro=esm-infra/focalOther threatsAffected
  • 2.30-0ubuntu2 – 2.31-0ubuntu9.18+esm1
18 affected builds
Fixed in–
Ubuntu Pro 18.04 LTSglibcpkg:deb/ubuntu/glibc?arch=source&distro=esm-infra/bionicOther threatsAffected
  • 2.26-0ubuntu2 – 2.27-3ubuntu1.6+esm6
16 affected builds
Fixed in–
Ubuntu Pro 16.04 LTSglibcpkg:deb/ubuntu/glibc?arch=source&distro=esm-infra/xenialOther threatsAffected
  • 2.21-0ubuntu4 – 2.23-0ubuntu11.3+esm9
23 affected builds
Fixed in–
Ubuntu Pro 14.04 LTSeglibcpkg:deb/ubuntu/eglibc?arch=source&distro=esm-infra-legacy/trustyOther threatsAffected
  • 2.17-93ubuntu4 – 2.19-0ubuntu6.15+esm4
29 affected builds
Fixed in–

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

Users and administrators should validate and sanitize any user-supplied values passed to the ,ccs= syntax extension in fopen mode strings to prevent exploitation. Avoid passing effectively empty strings to this syntax extension.

Description

A heap buffer overflow vulnerability exists in the GNU C Library (eglibc) version 2.45 or earlier when an effectively empty string is passed to the ,ccs= syntax extension of the mode argument in the fopen function. This flaw arises if the mode string input is attacker-controlled. This usage pattern is uncommon in typical GNU/Linux applications, and user-supplied ccs values should be validated before use.

References

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