openssl_encrypt CVE-2026-81721

The application must invoke openssl_encrypt to process an attacker-supplied encrypted file or keystore - for example, a file upload endpoint, a decryption API, or a keystore import feature that accepts user-controlled encrypted content. The vulnerability triggers during KDF parameter parsing from encrypted file metadata or keystore headers, before any key derivation or authentication occurs, so no account or session token is needed if that processing path is exposed to unauthenticated callers. Exploitation is limited by: (1) the target application must use jahlives/openssl_encrypt at a version prior to 1.4.9; (2) the attacker must be able to supply a crafted encrypted file as direct input to the library's parsing code. Applications that exclusively process encrypted files originating from trusted, internal sources are not practically exposed. Non-default or unusual deployment configurations are not required - any default use of the library's file or keystore parsing functions is vulnerable.

The CVSS 4.0 score of 8.7 (AV:N/AC:L/AT:N/PR:N/UI:N/VA:H) accurately characterizes the risk profile: the attack is network-reachable, requires no authentication or user interaction, and reliably produces a process crash. However, real-world impact is substantially bounded by the niche deployment footprint of jahlives/openssl_encrypt - this is not a widely deployed enterprise library like OpenSSL or BouncyCastle, significantly limiting the exposed attack surface. EPSS data was not provided and cannot be quantified from available intelligence. No KEV listing exists and no POC has been confirmed, so exploitation remains theoretical at time of analysis. The purely availability-only impact (C:N/I:N/A:H) means successful exploitation achieves service disruption only - no data exfiltration or integrity compromise is possible. Applications with memory limits enforced at the OS or container level (ulimit, cgroup) would cap blast radius but would still crash when the limit is reached.

An attacker submits a crafted encrypted file to a public-facing file import or decryption endpoint of an application built on openssl_encrypt. The crafted file's metadata declares an Argon2 memory parameter of, say, 64 GB. When the library parses the keystore header to begin decryption, it attempts to allocate 64 GB of RAM, rapidly exhausting system memory and crashing the process - taking the service offline. No authentication is required if the upload or decryption endpoint is publicly accessible.