CVE-2026-81699

openssl_encrypt versions before 1.4.9 fail to validate or bound the key derivation function (KDF) cost parameters embedded in encrypted files (CWE-770), so a crafted file can direct the software to run its KDF with excessively large cost settings. Because this occurs during pre-authentication processing, before the password is ever verified, any code path that feeds an attacker-supplied file to the tool can be triggered without credentials or user interaction, and over the network where the tool runs as a service. The result is unbounded memory and CPU consumption that can crash or wedge the process, giving an attacker a denial-of-service capability; no data compromise or code execution is described. Anyone running openssl_encrypt prior to 1.4.9 is affected, with the greatest exposure for automated jobs or services that decrypt files from untrusted sources. There is no known public proof-of-concept, the issue is not in CISA KEV, and EPSS places the 30-day exploitation probability at about 0.4% (29th percentile), so no active exploitation is currently evident; severity is CVSS 4.0 8.7 (High) with a network attack vector requiring no privileges or user interaction.

What to do: Upgrade to openssl_encrypt 1.4.9 or later. Where an immediate upgrade is not possible, apply resource limits (memory/CPU caps, timeouts) to the process handling encrypted files and avoid decrypting files from untrusted sources, particularly in services that accept uploaded encrypted files. Audit scripts, cron jobs, and applications for any use of openssl_encrypt on externally supplied files to confirm exposure.