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OpenSSL: EDIPARTYNAME NULL Pointer De-reference Vulnerability (CVE-2020-1971) (Windows)

Information

Severity

Severity

High

Family

Family

Denial of Service

CVSSv2 Base

CVSSv2 Base

7.1

CVSSv2 Vector

CVSSv2 Vector

AV:N/AC:M/Au:N/C:N/I:N/A:C

Solution Type

Solution Type

Vendor Patch

Created

Created

2 years ago

Modified

Modified

1 year ago

Summary

OpenSSL is prone to a Denial-of-Service (DoS) vulnerability.

Insight

Insight

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.

Affected Software

Affected Software

All OpenSSL 1.1.1 and 1.0.2 versions are affected by this issue. OpenSSL 1.1.0 is out of support and no longer receiving updates of any kind. The impact of this issue on OpenSSL 1.1.0 has not been analysed.

Detection Method

Detection Method

Checks if a vulnerable version is present on the target host.

Solution

Solution

OpenSSL 1.1.1 users should upgrade to 1.1.1i. OpenSSL 1.0.2 is out of support and no longer receiving public updates. Premium support customers of OpenSSL 1.0.2 should upgrade to 1.0.2x. Other users should upgrade to OpenSSL 1.1.1i.

Common Vulnerabilities and Exposures (CVE)