CVE-2023-6237: Excessive time spent checking invalid RSA public keys

Vulnerability summary

CVE-2023-6237 is a medium (CVSS 5.9) Unchecked Input for Loop Condition vulnerability in openssl. EPSS estimates a 2.30% chance of exploitation in the next 30 days, higher than 83.3% of scored vulnerabilities.

Timeline

1. 25-04-2024
   PublishedVulnerability first disclosed.
2. 14-10-2026
   Last modifiedVulnerability information updated.

Description

Issue summary: Checking excessively long invalid RSA public keys may take a long time. Impact summary: Applications that use the function EVP_PKEY_public_check() to check RSA public keys may experience long delays. Where the key that is being checked has been obtained from an untrusted source this may lead to a Denial of Service. When function EVP_PKEY_public_check() is called on RSA public keys, a computation is done to confirm that the RSA modulus, n, is composite. For valid RSA keys, n is a product of two or more large primes and this computation completes quickly. However, if n is an overly large prime, then this computation would take a long time. An application that calls EVP_PKEY_public_check() and supplies an RSA key obtained from an untrusted source could be vulnerable to a Denial of Service attack. The function EVP_PKEY_public_check() is not called from other OpenSSL functions however it is called from the OpenSSL pkey command line application. For that reason that application is also vulnerable if used with the '-pubin' and '-check' options on untrusted data. The OpenSSL SSL/TLS implementation is not affected by this issue. The OpenSSL 3.0 and 3.1 FIPS providers are affected by this issue.

• CWE-606Unchecked Input for Loop ConditionThe product does not properly check inputs that are used for loop conditions, potentially leading to a denial of service or other consequences because of excessive looping.