CVE-2026-81721 openssl_encrypt before 1.4.9 Denial of Service via KDF

High 8.7 Published 27 Aug 2026 Updated 1 Oct 2026

Attackers can cause denial of service by crafting malicious encrypted files with excessive KDF parameters, exhausting memory in the openssl_encrypt library.

Exploited in the wild: Not known
Login needed: Not needed
Attackable: Over the internet
Victim action needed: Not needed
Fix: Available

What is CVE-2026-81721?

CVE-2026-81721 is a high-severity denial of service vulnerability in Jahlives Openssl Encrypt, published on 27 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

Official description

openssl_encrypt before 1.4.9 fails to validate KDF cost parameters in encrypted file metadata and keystore headers, allowing attackers to trigger unbounded memory allocation. Attackers can craft malicious encrypted files declaring arbitrarily large Argon2, scrypt, or balloon KDF parameters to exhaust system memory and crash the process without authentication.

Weakness: CWE-400

Which versions are affected by CVE-2026-81721?

1 open source package ship an affected version, including openssl-encrypt. It affects 1 product.

Package	Affected	Fixed in
`openssl-encrypt` PyPI	All versions	`1.4.9`

Products include Jahlives Openssl Encrypt.

How do I fix CVE-2026-81721?

Upgrade openssl-encrypt to 1.4.9 or later.

Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.

Is CVE-2026-81721 being exploited?

There is no known exploitation of CVE-2026-81721 in the wild and no public exploit code.

All Jahlives Openssl Encrypt vulnerabilities

Sources

Also known as GHSA-7894-5gw8-69hr, GHSA-9pph-4h37-568j, PYSEC-2026-3803.