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HIGH

Infinite loop in BN_mod_sqrt() reachable when parsing certificates

Published Mar 15, 2022

Description

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).

Affected products

Remediation

Red Hat statement

While Red Hat initially stated not to be directly affected by this flaw, after further investigation we found that the versions of OpenSSL as shipped in Red Hat Enterprise Linux 6, 7, and 8 are vulnerable to a denial of service attack through malicious Elliptic Curve parameters. During processing of the parameters OpenSSL will call BN_mod_sqrt() with invalid arguments, causing the process to enter an infinite loop. The invalid EC parameters can be provided to OpenSSL through X.509 certificates (used in TLS connections), through public and private keys, through certificate signing requests and other places where applications process Elliptic Curve parameters. The flaw has been rated as having a security impact of Important. A future update will address this issue in Red Hat Enterprise Linux 6, 7 and 8.

Red Hat mitigation

Red Hat has investigated whether a possible mitigation exists for this issue, and has not been able to identify a practical example. Please update the affected package as soon as possible.

Weaknesses (1)

CWE-835

References (46)

Change history (0)

No recorded changes yet.

Sources
CVE.org / MITRE
Status PUBLISHED
Assigner openssl
Published Mar 15, 2022
Updated May 22, 2026
Reserved Feb 28, 2022
Link CVE-2022-0778
CISA Vulnrichment
Updated May 22, 2026
NVD
Status Modified
Modified Jun 17, 2026
Link CVE-2022-0778
Red Hat
Severity Important
Public date Mar 15, 2022
Links CVE-2022-0778 - Bugzilla
GHSA-X3MH-JVJW-3XWX