openssl_encrypt versions before 1.4.9 store an unkeyed SHA-256 hash of the plaintext in the cleartext file header metadata. Attackers can read this hash without the password to confirm guessed plaintexts offline or fingerprint identical plaintexts across separately-encrypted files.
HIGH
Vulnerability intelligence
CVE-2026-81688
CVSS 4.08.7
SeverityHigh
Known exploitedNo
NVD references:
Primary source: NIST National Vulnerability Database