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MEDIUM

EDIPARTYNAME NULL pointer dereference

Published Dec 8, 2020

Description

The X.509 GeneralName type is a generic type for representing different types of names. One of those name types is known as EDIPartyName. OpenSSL provides a function GENERAL_NAME_cmp which compares different instances of a GENERAL_NAME to see if they are equal or not. This function behaves incorrectly when both GENERAL_NAMEs contain an EDIPARTYNAME. A NULL pointer dereference and a crash may occur leading to a possible denial of service attack. OpenSSL itself uses the GENERAL_NAME_cmp function for two purposes: 1) Comparing CRL distribution point names between an available CRL and a CRL distribution point embedded in an X509 certificate 2) When verifying that a timestamp response token signer matches the timestamp authority name (exposed via the API functions TS_RESP_verify_response and TS_RESP_verify_token) If an attacker can control both items being compared then that attacker could trigger a crash. For example if the attacker can trick a client or server into checking a malicious certificate against a malicious CRL then this may occur. Note that some applications automatically download CRLs based on a URL embedded in a certificate. This checking happens prior to the signatures on the certificate and CRL being verified. OpenSSL's s_server, s_client and verify tools have support for the "-crl_download" option which implements automatic CRL downloading and this attack has been demonstrated to work against those tools. Note that an unrelated bug means that affected versions of OpenSSL cannot parse or construct correct encodings of EDIPARTYNAME. However it is possible to construct a malformed EDIPARTYNAME that OpenSSL's parser will accept and hence trigger this attack. All OpenSSL 1.1.1 and 1.0.2 versions are affected by this issue. Other OpenSSL releases are out of support and have not been checked. Fixed in OpenSSL 1.1.1i (Affected 1.1.1-1.1.1h). Fixed in OpenSSL 1.0.2x (Affected 1.0.2-1.0.2w).

Affected products

Remediation

Red Hat statement

This is a flaw in the GENERAL_NAME_cmp function of openssl which can be triggered when both its arguments are of the same type i.e. EDIPARTYNAME. 1. Red Hat does not ship any applications compiled with openssl, which used the above function in a vulnerable way. 2. OpenSSL itself uses the GENERAL_NAME_cmp function for two purposes, when comparing CRL distribution point names between an available CRL and a CRL distribution point embedded in an X509 certificate and when verifying that a timestamp response token signer matches the timestamp authority name (exposed via the API functions TS_RESP_verify_response and TS_RESP_verify_token). If an attacker can control both items being compared then that attacker could trigger a crash. For example, if the attacker can trick a client or server into checking a malicious certificate against a malicious CRL then a crash may be triggered. Third party applications compiled with openssl using the function GENERAL_NAME_cmp in a vulnerable way are affected by this flaw. GENERAL_NAME_cmp was added in 0.9.8k, therefore older versions of openssl are not affected by this flaw.

Red Hat mitigation

Applications not using the GENERAL_NAME_cmp of openssl are not vulnerable to this flaw. Even when this function is used, if the attacker can control both the arguments of this function, only then the attacker could trigger a crash.

Metrics

Weaknesses (1)

CWE-476

NULL Pointer Dereference

References (30)

Change history (0)

No recorded changes yet.

Sources
CVE.org / MITRE
Status PUBLISHED
Assigner openssl
Published Dec 8, 2020
Updated May 29, 2026
Reserved Dec 3, 2019
Link CVE-2020-1971
CISA Vulnrichment
Updated May 29, 2026
NVD
Status Modified
Modified Jun 17, 2026
Link CVE-2020-1971
Red Hat
Severity Important
Public date Dec 8, 2020
Links CVE-2020-1971 - Bugzilla