Excessive time spent checking DH q parameter value

Summary

Issue summary: Checking excessively long DH keys or parameters may be very slow. Impact summary: Applications that use the functions DH_check(), DH_check_ex() or EVP_PKEY_param_check() to check a DH key or DH parameters may experience long delays. Where the key or parameters that are being checked have been obtained from an untrusted source this may lead to a Denial of Service. The function DH_check() performs various checks on DH parameters. After fixing CVE-2023-3446 it was discovered that a large q parameter value can also trigger an overly long computation during some of these checks. A correct q value, if present, cannot be larger than the modulus p parameter, thus it is unnecessary to perform these checks if q is larger than p. An application that calls DH_check() and supplies a key or parameters obtained from an untrusted source could be vulnerable to a Denial of Service attack. The function DH_check() is itself called by a number of other OpenSSL functions. An application calling any of those other functions may similarly be affected. The other functions affected by this are DH_check_ex() and EVP_PKEY_param_check(). Also vulnerable are the OpenSSL dhparam and pkeyparam command line applications when using the "-check" option. The OpenSSL SSL/TLS implementation is not affected by this issue. The OpenSSL 3.0 and 3.1 FIPS providers are not affected by this issue.

Timeline

1. Jul 31, 2023, 3:34 PM UTCCVE published
2. Apr 23, 2025, 1:26 PM UTCCISA SSVC assessment

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

3. Oct 14, 2026, 9:13 PM UTCRecord last updated

Affected versions

• OpenSSL OpenSSL

  From 3.1.0 · fixed in 3.1.2; From 3.0.0 · fixed in 3.0.10; From 1.1.1 · fixed in 1.1.1v; From 1.0.2 · fixed in 1.0.2zi

References 5