Infinite loop in BN_mod_sqrt() reachable when parsing certificates

Summary

The BN_mod_sqrt() function, which computes a modular square root, contains a bug that can cause it to loop forever for non-prime moduli. Internally this function is used when parsing certificates that contain elliptic curve public keys in compressed form or explicit elliptic curve parameters with a base point encoded in compressed form. It is possible to trigger the infinite loop by crafting a certificate that has invalid explicit curve parameters. Since certificate parsing happens prior to verification of the certificate signature, any process that parses an externally supplied certificate may thus be subject to a denial of service attack. The infinite loop can also be reached when parsing crafted private keys as they can contain explicit elliptic curve parameters. Thus vulnerable situations include: - TLS clients consuming server certificates - TLS servers consuming client certificates - Hosting providers taking certificates or private keys from customers - Certificate authorities parsing certification requests from subscribers - Anything else which parses ASN.1 elliptic curve parameters Also any other applications that use the BN_mod_sqrt() where the attacker can control the parameter values are vulnerable to this DoS issue. In the OpenSSL 1.0.2 version the public key is not parsed during initial parsing of the certificate which makes it slightly harder to trigger the infinite loop. However any operation which requires the public key from the certificate will trigger the infinite loop. In particular the attacker can use a self-signed certificate to trigger the loop during verification of the certificate signature. This issue affects OpenSSL versions 1.0.2, 1.1.1 and 3.0. It was addressed in the releases of 1.1.1n and 3.0.2 on the 15th March 2022. Fixed in OpenSSL 3.0.2 (Affected 3.0.0,3.0.1). Fixed in OpenSSL 1.1.1n (Affected 1.1.1-1.1.1m). Fixed in OpenSSL 1.0.2zd (Affected 1.0.2-1.0.2zc).

Timeline

1. Mar 15, 2022, 5:05 PM UTCCVE published
2. May 22, 2026, 1:27 PM UTCCISA SSVC assessment

   Exploitation: none · Automatable: yes · Technical impact: partial

3. Oct 14, 2026, 12:12 PM UTCRecord last updated
4. Oct 22, 2026EPSS reached 10%

   FIRST estimates at least a 10% chance of exploitation in the next 30 days

Affected versions

• OpenSSL OpenSSL

  Fixed in OpenSSL 3.0.2 (Affected 3.0.0,3.0.1), Fixed in OpenSSL 1.1.1n (Affected 1.1.1-1.1.1m), Fixed in OpenSSL 1.0.2zd (Affected 1.0.2-1.0.2zc)

• mariadbBitnami

  From 10.2.0 · fixed in 10.2.42; From 10.3.0 · fixed in 10.3.33; From 10.4.0 · fixed in 10.4.23; From 10.5.0 · fixed in 10.5.14; From 10.6.0 · fixed in 10.6.6; From 10.7.0 · fixed in 10.7.2

• mariadb-minBitnami

  From 10.2.0 · fixed in 10.2.42; From 10.3.0 · fixed in 10.3.33; From 10.4.0 · fixed in 10.4.23; From 10.5.0 · fixed in 10.5.14; From 10.6.0 · fixed in 10.6.6; From 10.7.0 · fixed in 10.7.2

• mysql-clientBitnami

  From 10.2.0 · fixed in 10.2.42; From 10.3.0 · fixed in 10.3.33; From 10.4.0 · fixed in 10.4.23; From 10.5.0 · fixed in 10.5.14; From 10.6.0 · fixed in 10.6.6; From 10.7.0 · fixed in 10.7.2

• nodeBitnami

  From 12.0.0 · fixed in 12.12.1; From 12.13.0 · fixed in 12.22.11; From 14.0.0 · fixed in 14.14.1; From 14.15.0 · fixed in 14.19.1; From 16.0.0 · fixed in 16.12.1; From 16.13.0 · fixed in 16.14.2; From 17.0.0 · fixed in 17.7.2

• node-minBitnami

  From 12.0.0 · fixed in 12.12.1; From 12.13.0 · fixed in 12.22.11; From 14.0.0 · fixed in 14.14.1; From 14.15.0 · fixed in 14.19.1; From 16.0.0 · fixed in 16.12.1; From 16.13.0 · fixed in 16.14.2; From 17.0.0 · fixed in 17.7.2

• openssl-srccrates.io

  From 300.0.0 · fixed in 300.0.5

• openssl-srccrates.io

  fixed in 111.18.0

• openssl-srccrates.io

  From 0.0.0-0 · fixed in 111.18.0; From 300.0.0 · fixed in 300.0.5

References 25