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CVE-2026-18374

• Severity: medium (CVSS 4.9 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.1% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-08-27 · updated 2026-09-03
• Weakness: CWE-787

Description

Passing an effectively empty string to the `,ccs=` syntax extension of the mode argument in the `fopen` function in the GNU C Library version 2.45 or earlier may result in a heap buffer overflow when the mode string input to the function is attacker controlled. This usage pattern is not seen in applications in common GNU/Linux distributions and applications that process user-supplied values for `ccs` should not pass them through without validation.

Affected products

• GNU C Library (glibc): before 2.45 — fixed in 2.45

How to fix

Upgrade to a fixed version: GNU C Library (glibc) 2.45. Check the vendor advisory for mitigations.

References

• https://sourceware.org/bugzilla/show_bug.cgi?id=34574
• https://sourceware.org/git/?p=glibc.git;a=blob_plain;f=advisories/GLIBC-SA-2026-0015
• http://www.openwall.com/lists/oss-security/2026/08/27/6

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