Description
The OpenSSL public API function X509_issuer_and_serial_hash() attempts to create a unique hash value based on the issuer and serial number data contained within an X509 certificate. However it fails to correctly handle any errors that may occur while parsing the issuer field (which might occur if the issuer field is maliciously constructed). This may subsequently result in a NULL pointer deref and a crash leading to a potential denial of service attack. The function X509_issuer_and_serial_hash() is never directly called by OpenSSL itself so applications are only vulnerable if they use this function directly and they use it on certificates that may have been obtained from untrusted sources. OpenSSL versions 1.1.1i and below are affected by this issue. Users of these versions should upgrade to OpenSSL 1.1.1j. OpenSSL versions 1.0.2x and below are affected by this issue. However 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 1.0.2y. Other users should upgrade to 1.1.1j. Fixed in OpenSSL 1.1.1j (Affected 1.1.1-1.1.1i). Fixed in OpenSSL 1.0.2y (Affected 1.0.2-1.0.2x).
Published: 2021-02-16
Score: 5.9 Medium
EPSS: < 1% Very Low
KEV: No
Impact: n/a
Action: n/a
AI Analysis

No analysis available yet.

Remediation

No remediation available yet.

Tracking

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Advisories
Source ID Title
Debian DLA Debian DLA DLA-2563-1 openssl security update
Debian DLA Debian DLA DLA-2565-1 openssl1.0 security update
Debian DSA Debian DSA DSA-4855-1 openssl security update
EUVD EUVD EUVD-2021-1630 The OpenSSL public API function X509_issuer_and_serial_hash() attempts to create a unique hash value based on the issuer and serial number data contained within an X509 certificate. However it fails to correctly handle any errors that may occur while parsing the issuer field (which might occur if the issuer field is maliciously constructed). This may subsequently result in a NULL pointer deref and a crash leading to a potential denial of service attack. The function X509_issuer_and_serial_hash() is never directly called by OpenSSL itself so applications are only vulnerable if they use this function directly and they use it on certificates that may have been obtained from untrusted sources. OpenSSL versions 1.1.1i and below are affected by this issue. Users of these versions should upgrade to OpenSSL 1.1.1j. OpenSSL versions 1.0.2x and below are affected by this issue. However 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 1.0.2y. Other users should upgrade to 1.1.1j. Fixed in OpenSSL 1.1.1j (Affected 1.1.1-1.1.1i). Fixed in OpenSSL 1.0.2y (Affected 1.0.2-1.0.2x).
Github GHSA Github GHSA GHSA-84rm-qf37-fgc2 Integer Overflow in openssl-src
Ubuntu USN Ubuntu USN USN-4738-1 OpenSSL vulnerabilities
Ubuntu USN Ubuntu USN USN-4745-1 OpenSSL vulnerabilities
History

Tue, 24 Feb 2026 16:15:00 +0000

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}


Sun, 08 Sep 2024 18:30:00 +0000

Type Values Removed Values Added
CPEs cpe:/a:redhat:acm:2.2::el7

Mon, 19 Aug 2024 22:15:00 +0000

Type Values Removed Values Added
CPEs cpe:/a:redhat:acm:2.2::el7
cpe:/a:redhat:acm:2.2::el8

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cve-icon MITRE

Status: PUBLISHED

Assigner: openssl

Published:

Updated: 2024-09-16T22:39:57.576Z

Reserved: 2021-01-12T00:00:00.000Z

Link: CVE-2021-23841

cve-icon Vulnrichment

Updated: 2024-08-03T19:14:09.152Z

cve-icon NVD

Status : Modified

Published: 2021-02-16T17:15:13.377

Modified: 2024-11-21T05:51:55.460

Link: CVE-2021-23841

cve-icon Redhat

Severity : Moderate

Publid Date: 2021-02-16T00:00:00Z

Links: CVE-2021-23841 - Bugzilla

cve-icon OpenCVE Enrichment

No data.

Weaknesses