Bug 2526299

Summary: CVE-2026-18374 glibc: glibc: Heap buffer overflow via attacker-controlled fopen mode string [fedora-all]
Product: [Fedora] Fedora Reporter: Ganesh <gnaik>
Component: glibcAssignee: Carlos O'Donell <codonell>
Status: CLOSED ERRATA QA Contact: Fedora Extras Quality Assurance <extras-qa>
Severity: medium Docs Contact:
Priority: medium    
Version: rawhideCC: arjun, codonell, dj, fberat, fweimer, jlaw, josmyers, mcermak, mcoufal, mfabian, pfrankli, sipoyare, skolosov, suraj.ghimire7
Target Milestone: ---Keywords: Security, SecurityTracking
Target Release: ---   
Hardware: Unspecified   
OS: Unspecified   
Whiteboard: {"flaws": ["7dfb1b13-46a5-4d39-933c-75cda64a755a"]}
Fixed In Version: glibc-2.44.9000-3.fc46 glibc-2.44-2.fc45 glibc-2.43-9.fc44 glibc-2.42-17.fc43 Doc Type: ---
Doc Text:
Story Points: ---
Clone Of: Environment:
Last Closed: 2026-10-16 13:05:10 UTC Type: ---
Regression: --- Mount Type: ---
Documentation: --- CRM:
Verified Versions: Category: ---
oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
Embargoed:
Bug Depends On:    
Bug Blocks: 2525256    

Description Ganesh 2026-08-31 14:05:01 UTC
Disclaimer: Community trackers are created by Red Hat Product Security team on a best effort basis. Package maintainers are required to ascertain if the flaw indeed affects their package, before starting the update process.

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.