CVE-2025-15281: 
NixOS vulnerability analysis and mitigation

CVE-2025-15281 is a use of uninitialized resource vulnerability (CWE-908) in the GNU C Library (glibc) wordexp function, tracked under advisory GLIBC-SA-2026-0003. When wordexp is called with both WRDE_REUSE and WRDE_APPEND flags simultaneously, the function may return uninitialized memory in the we_wordv member; subsequent calls to wordfree may then abort the process. The vulnerability affects glibc versions 2.0 through 2.42 and was publicly disclosed on January 20, 2026. It carries a CVSS v3.1 base score of 7.5 (High) (oss-security, Feedly).

The root cause is classified as CWE-908 (Use of Uninitialized Resource). The WRDE_REUSE combined with WRDE_APPEND implementation fails to clear the we_wordc member of the wordexp_t structure before adding new words; as a result, a leading we_wordc count of entries are skipped under the assumption they are already initialized, but they are not — they contain raw contents of a realloc-expanded pointer array. An attacker or application that triggers this code path via a network-accessible service calling wordexp with these flags can cause the process to dereference invalid pointers or trigger a malloc abort when wordfree is called. The vulnerable commit dates back to glibc 1.93-260 (commit 8f2ece695d8822e9ecc63ecd157e90bf17a6fe65), and the fix was introduced in commit 80cc58ea2de214f85b0a1d902a3b668ad2ecb302 for version 2.43 (oss-security, glibc Bugzilla).

Successful exploitation results in a denial of service (DoS) through process abort, impacting the availability of any application or service that uses the vulnerable wordexp call pattern. There is no confidentiality or integrity impact — the CVSS vector reflects high availability impact only. Because glibc is a foundational library present across virtually all Linux-based systems, the affected asset scope is broad, spanning servers, appliances, and embedded systems running glibc 2.0–2.42, including IBM Netezza Appliance, IBM API Connect, IBM CICS Transaction Gateway for Multiplatforms, and Microsoft Azure Linux 3 (AZL3) (Feedly, IBM Netezza Advisory).

The primary remediation is to upgrade GNU C Library (glibc) to version 2.43 or later, which contains the fix commit 80cc58ea2de214f85b0a1d902a3b668ad2ecb302 (oss-security, glibc Bugzilla). Major Linux distributions have released patched packages: Red Hat (RHSA-2026:2786, RHSA-2026:3228, RHSA-2026:4501, RHSA-2026:4772, RHSA-2026:4943, RHSA-2026:18139), Ubuntu (USN-8005-1), Debian (DLA-4621-1), Fedora, Mageia, openSUSE, AlmaLinux, Rocky Linux, and Oracle Linux have all issued updates (Red Hat Errata, Ubuntu Advisory). IBM has also released patches for affected products including Netezza Appliance, API Connect, and CICS Transaction Gateway for Multiplatforms (IBM Netezza Advisory, IBM API Connect Advisory, IBM CICS Advisory). As a workaround where patching is not immediately possible, avoid using wordexp with the combined WRDE_REUSE | WRDE_APPEND flags in application code.

The vulnerability was reported by Vitaly Simonovich and disclosed by Carlos O'Donell of Red Hat via the oss-security mailing list on January 20, 2026 (oss-security). The glibc maintainers noted in the advisory that the affected flag combination has never worked correctly, suggesting real-world impact is limited. Community discussion was observed on the GNU Tools Weekly Mastodon account and the Solus Linux project update thread, reflecting routine awareness rather than alarm (Feedly).