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CVE-2021-33913

9.8 · CRITICAL

libspf2 before 1.2.11 has a heap-based buffer overflow that might allow remote attackers to execute arbitrary code (via an unauthenticated e-mail message from anywhere on the Internet) with a craft…

Published Jan 19, 2022CWE-787EPSS 9.64%

Overview

CVE-2021-33913 is a critical-severity vulnerability. It was published on January 19, 2022 and has a CVSS 3.1 base score of 9.8 (CRITICAL).

This vulnerability has a CVSS 3.1 base score of 9.8, rated CRITICAL. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.

Technical description

libspf2 before 1.2.11 has a heap-based buffer overflow that might allow remote attackers to execute arbitrary code (via an unauthenticated e-mail message from anywhere on the Internet) with a crafted SPF DNS record, because of SPF_record_expand_data in spf_expand.c. The amount of overflowed data depends on the relationship between the length of an entire domain name and the length of its leftmost label. The vulnerable code may be part of the supply chain of a site's e-mail infrastructure (e.g., with additional configuration, Exim can use libspf2; the Postfix web site links to unofficial patches for use of libspf2 with Postfix; older versions of spfquery relied on libspf2) but most often is not.

Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

References

GitHubgithub.com/shevek/libspf2/tree/8131fe140704eaae695e76b5cd09e39bd1dd220bReflists.debian.org/debian-lts-announce/2022/01/msg00015.htmlRefnathanielbennett.com/blog/libspf2-cve-jan-2022-disclosureRefsecurity.gentoo.org/glsa/202401-22GitHubgithub.com/shevek/libspf2/tree/8131fe140704eaae695e76b5cd09e39bd1dd220bReflists.debian.org/debian-lts-announce/2022/01/msg00015.htmlRefnathanielbennett.com/blog/libspf2-cve-jan-2022-disclosureRefsecurity.gentoo.org/glsa/202401-22

How CyberStrike helps

Frequently asked questions

What is CVE-2021-33913?

CVE-2021-33913 is a critical-severity vulnerability. It was published on January 19, 2022 and has a CVSS 3.1 base score of 9.8 (CRITICAL).

How severe is CVE-2021-33913?

This vulnerability has a CVSS 3.1 base score of 9.8, rated CRITICAL. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.

How do I fix or remediate CVE-2021-33913?

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

How can CyberStrike help with CVE-2021-33913?

CyberStrike is an open-source, AI-augmented pentesting engine. Rather than flag a version number, it tests whether an issue like CVE-2021-33913 is actually reachable in your own applications and APIs, then verifies each finding before reporting it. That tells you if the weakness is a real, exploitable risk in your environment or a false positive you can safely deprioritize.

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