CVE-2026-81687: openssl_encrypt before 1.4.9 Denial of Service via KDF
opensslencrypt versions before 1.4.9 fail to enforce a time ceiling on key derivation function iteration counts specified in file metadata. Attackers can craft files with extremely high KDF iteration counts to consume CPU resources for unbounded periods before password verification occurs.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
openssl_encryptto a version that resolves this vulnerability.Fixed in 1.4.9 - Compensating control
Mitigate the CPU-DoS by limiting or throttling decryption/password-verification workload (e.g., rate-limit requests that trigger openssl_encrypt, and/or constrain CPU resources) until all affected openssl_encrypt instances are upgraded to 1.4.9 or later.
Event History
Frequently Asked Questions
Who is exposed to this denial-of-service issue?
Systems using openssl_encrypt before 1.4.9 are exposed when they process attacker-crafted encrypted files. The attacker can cause CPU consumption before password verification occurs.
Does exploitation require authentication or user interaction?
No authentication is required, but user interaction is required according to the supplied CVSS vector. Exploitation depends on a crafted file being processed by the affected software.
How can I tell whether a file may trigger the issue?
Affected files specify extremely high key derivation function iteration counts in their metadata. Processing such a file can consume CPU resources for an unbounded period before the password is checked.