Medium [CVE-2026-18374] Heap buffer overflow via attacker-controlled fopen mode string
This medium-severity Red Hat Linux advisory covers CVE-2026-18374 affecting Red Hat Enterprise Linux 10, Red Hat Enterprise Linux 6, Red Hat Enterprise Linux 7.
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Summary
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. This vulnerability could allow an attacker with local access to trigger a heap buffer overflow by manipulating how the `fopen` function handles certain input.
This could lead to minor disruptions in system operations or limited access to sensitive information. Exploitation is highly complex as this specific usage pattern is not common in applications within typical Red Hat Enterprise Linux environments, significantly limiting its practical applicability.
Red Hat severity: Moderate — CVSS 4.9 (CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:L). Weakness: CWE-134.
Affected Red Hat products: Red Hat Enterprise Linux 10; Red Hat Enterprise Linux 6; Red Hat Enterprise Linux 7; Red Hat Enterprise Linux 8; Red Hat Enterprise Linux 9; Red Hat Hardened Images. Red Hat lists Red Hat Hardened Images as not affected.
Red Hat does not currently list a fixing RHSA for this CVE.
Affected versions
No affected-version range was extracted from the source record. The vendor advisory is authoritative — check it before change work.
Official advisory · high-confidence parse· fetched 1 hour ago·verify at source
Fixed versions
No fixed release is recorded yet. That does not prove no patch exists — confirm against the vendor advisory.
Official advisory · high-confidence parse· fetched 1 hour ago·verify at source
Mitigation checklist
- Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability.
Official advisory · high-confidence parse· fetched 1 hour ago·verify at source
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