CVE-2026-81688: openssl_encrypt before 1.4.9 Plaintext Confirmation Oracle via SHA-256

Severity: high (CVSS 7.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.3% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-08-27 · updated 2026-09-02
Weakness: CWE-311

Description

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.

Affected products

jahlives openssl_encrypt: before 1.4.9 — fixed in 1.4.9

How to fix

Upgrade to a fixed version: jahlives openssl_encrypt 1.4.9. Check the vendor advisory for mitigations.

References

https://github.com/jahlives/openssl_encrypt/security/advisories/GHSA-7c3q-gp4v-q29q
https://www.vulncheck.com/advisories/openssl-encrypt-before-1.4.9-plaintext-confirmation-oracle-via-sha-256

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