CVE-2025-15469: 
OpenSSL vulnerability analysis and mitigation

CVE-2025-15469 is a data integrity bypass vulnerability in the OpenSSL openssl dgst command-line tool that silently truncates input data to 16MB when using one-shot signing algorithms and reports success instead of an error. It affects OpenSSL versions 3.5.0–3.5.4 and 3.6.0, while OpenSSL 3.4, 3.3, 3.0, 1.1.1, and 1.0.2 are not affected. The vulnerability was disclosed on January 27, 2026, with patches released the same day. It carries a CVSS v3.1 base score of 5.5 (Medium) (Red Hat Advisory, OpenSSL Advisory).

The root cause is improper validation of specified input quantity (CWE-1284) combined with improper verification of cryptographic signatures (CWE-347). The bio_to_mem() helper function in apps/lib/apps.c used a signed int for the buffer length and max length, capping reads at 16MB (16 × 1024 × 1024 bytes); when input exceeded this limit, the function silently stopped reading and returned the truncated buffer without signaling an error to the caller in do_fp_oneshot_sign(). This affects only the openssl dgst command-line tool when used with one-shot signing algorithms (Ed25519, Ed448, ML-DSA-44, ML-DSA-65, ML-DSA-87); streaming digest algorithms and library API users are unaffected. The fix changes bio_to_mem() to return an error (0) when input exceeds the 16MB limit rather than silently truncating (GitHub Commit 310f305, GitHub Commit a7936fa).

The primary impact is an integrity gap: users signing or verifying files larger than 16MB with affected one-shot algorithms may believe the entire file is authenticated, while any data beyond the first 16MB remains unauthenticated and can be modified without detection. This risk is confined to workflows where both signing and verification are performed using the affected openssl dgst command-line tool — verifiers using library APIs will reject such signatures, limiting the attack surface. There is no confidentiality or availability impact; the vulnerability is local and requires low privileges to exploit (Red Hat Advisory, OpenSSL Advisory).

1. Identify a vulnerable workflow: Confirm the target environment uses OpenSSL 3.5.0–3.5.4 or 3.6.0 and relies on openssl dgst with Ed25519, Ed448, ML-DSA-44, ML-DSA-65, or ML-DSA-87 for signing and verifying files larger than 16MB.
2. Prepare a crafted file: Create or obtain a legitimate file larger than 16MB that has been signed using the affected openssl dgst -sign command. The signature covers only the first 16MB.
3. Modify trailing data: Alter any content in the file beyond the 16MB boundary (e.g., append or replace bytes after offset 16,777,216). This data is not covered by the signature.
4. Submit for verification: Present the modified file to a verifier that also uses the affected openssl dgst -verify command. The verifier will only check the first 16MB and report the signature as valid, despite the modified trailing content.
5. Achieve integrity bypass: The attacker's modifications beyond 16MB pass signature verification undetected, enabling injection of malicious content, altered configuration, or tampered data in the unauthenticated portion of the file (Red Hat Advisory, OpenSSL Advisory).

Upgrade OpenSSL to version 3.5.5 or later (for 3.5.x users) or 3.6.1 or later (for 3.6.x users); earlier branches (3.4, 3.3, 3.0, 1.1.1, 1.0.2) are not affected and do not require updates. As a workaround, replace openssl dgst CLI usage with OpenSSL library API calls for signing and verifying files, or switch to streaming digest algorithms which are unaffected by this issue. Red Hat has addressed this via RHSA-2026:1472 (RHEL 10) and RHSA-2026:1473 (RHEL 9); IBM has issued advisories for affected products including API Connect and Netezza Appliance (OpenSSL Advisory, Red Hat Bugzilla, IBM API Connect).

The vulnerability was part of a batch of 12 OpenSSL CVEs disclosed in January 2026, several of which were discovered by an AI-assisted security research team (Aisle), generating notable media coverage about AI's role in vulnerability discovery (Tom's Hardware, TechRadar). The OpenSSL project and community discussed the release on the openssl-users and openssl-project mailing lists, and the fix was praised for its clean resolution (OpenSSL Users List). Security news outlets including SecurityOnline and CyberSecurityNews covered the broader batch of OpenSSL vulnerabilities, though CVE-2025-15469 itself received less attention than the higher-severity issues in the same release.