Executive brief
openssl_encrypt is a file encryption tool that uses key derivation functions to convert user passwords into encryption keys. Before version 1.4.9, the tool fails to limit the computational time required for key derivation, allowing attackers to craft malicious files that force excessive CPU consumption for extended periods—potentially hours or days—before the password is even checked. This creates a denial-of-service vulnerability where legitimate users cannot decrypt files without freezing their systems.
Technical details
The vulnerability is an uncontrolled resource consumption (CWE-400) flaw in the decrypt path. The tool reads key derivation function (KDF) iteration counts from attacker-controlled file metadata and enforced a memory ceiling (8 GiB) but failed to enforce a corresponding time ceiling. An attacker can craft a file declaring extremely high KDF iteration counts (e.g., 2^31 rounds for hash-based KDF or argon2 time_cost = 2^31 with minimal memory) that passes the memory check yet causes CPU-bound computation lasting from 1,600 seconds (hash case) to 10^16 seconds (argon2 case) before password verification occurs. The attack is network-reachable if files are transmitted or shared, and requires no authentication. Version 1.4.9 and later enforce a hard 120-second time ceiling, overridable only via explicit user flag or interactive confirmation.
Affected products
- jahlives openssl_encrypt before 1.4.9
Timeline
- 2026-08-12: disclosed: GitHub Security Advisory GHSA-rv6w-7hq9-pr74 published
- 2026-08-27: advisory: CVE-2026-81687 published on NVD