OpenSSL 1.0.2 < 1.0.2x Null Pointer Dereference Vulnerability

medium Nessus Plugin ID 144053
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Synopsis

The remote service is affected by a null pointer dereference vulnerability.

Description

The version of tested product installed on the remote host is prior to tested version. It is, therefore, affected by a vulnerability as referenced in the 1.0.2x advisory.

- 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). (CVE-2020-1971)

Note that Nessus has not tested for this issue but has instead relied only on the application's self-reported version number.

Solution

Upgrade to OpenSSL version 1.0.2x or later.

See Also

http://www.nessus.org/u?101e8ed5

https://www.openssl.org/news/secadv/20201208.txt

Plugin Details

Severity: Medium

ID: 144053

File Name: openssl_1_0_2x.nasl

Version: 1.6

Type: remote

Family: Web Servers

Published: 12/10/2020

Updated: 6/3/2021

Dependencies: openssl_version.nasl

Risk Information

CVSS Score Source: CVE-2020-1971

VPR

Risk Factor: Medium

Score: 6.1

CVSS v2

Risk Factor: Medium

Base Score: 4.3

Temporal Score: 3.2

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

Temporal Vector: E:U/RL:OF/RC:C

CVSS v3

Risk Factor: Medium

Base Score: 5.9

Temporal Score: 5.2

Vector: CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H

Temporal Vector: E:U/RL:O/RC:C

Vulnerability Information

CPE: cpe:/a:openssl:openssl

Required KB Items: openssl/port

Exploit Ease: No known exploits are available

Patch Publication Date: 12/8/2020

Vulnerability Publication Date: 12/8/2020

Reference Information

CVE: CVE-2020-1971

IAVA: 2020-A-0566-S