← Vulnerability feed

Vulnerability record · CVE-2021-33913 · published 19 January 2022

CVE-2021-33913: Libspf2 project libspf2 out-of-bounds write vulnerability

LLibspf2 Project · Libspf2

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.

9.8 CVSS 3.1 Critical EPSS 9.6% · top 4.7% CWE-787 · Out-of-bounds write
9.8CVSS 3.1 base score, v2 9.3
9.6%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
8References, 2 tagged exploit
17 Jun 2026Last modified by NVD

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.

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://github.com/shevek/libspf2/tree/8131fe140704eaae695e76b5cd09e39bd1dd220b Third Party Advisory
https://lists.debian.org/debian-lts-announce/2022/01/msg00015.html Mailing ListThird Party Advisory
https://nathanielbennett.com/blog/libspf2-cve-jan-2022-disclosure ExploitThird Party Advisory
https://security.gentoo.org/glsa/202401-22
https://github.com/shevek/libspf2/tree/8131fe140704eaae695e76b5cd09e39bd1dd220b Third Party Advisory
https://lists.debian.org/debian-lts-announce/2022/01/msg00015.html Mailing ListThird Party Advisory
https://nathanielbennett.com/blog/libspf2-cve-jan-2022-disclosure ExploitThird Party Advisory
https://security.gentoo.org/glsa/202401-22

Track CVE-2021-33913 inside VULONE

Watch it alongside the ransomware crews, C2 infrastructure and forum chatter that reference it, query it through the API and pull it into your SIEM over TAXII.

Start free Open in platform

Related vulnerabilities

Same products first, then exploited flaws of the same weakness class.

9.8CVE-2021-33912Libspf2 project libspf2 out-of-bounds write vulnerabilitylibspf2 before 1.2.11 has a four-byte heap-based buffer overflow that might allow remote attackers to execute arbitrary code (via an unauthenticated …EPSS 9.6%8.8CVE-2023-42118Exim libspf2 SPF macro parsing integer underflow enables remote code executionExim's libspf2 does not properly validate user-supplied data when parsing SPF macros, causing an integer underflow before a memory write. This allows…EPSS 52%analysed8.8CVE-2026-53266Linux kernel ebtables SNAT out-of-bounds write in ARP rewriteThe ebtables SNAT target rewrites the ARP sender hardware address via skb_store_bits() without first making that range writable. When the ARP SHA byt…KEVEPSS 0.65%analysed8.8CVE-2026-87491Google Chrome V8 out-of-bounds write enables sandbox code executionChrome before 153.0.8010.36 contains an out-of-bounds write in the V8 JavaScript engine. A crafted HTML page can trigger the memory corruption, and b…KEVEPSS 3.1%analysed9.8CVE-2025-25249Fortinet FortiOS and FortiSwitchManager heap buffer overflow via crafted packetsA heap-based buffer overflow (CWE-122/CWE-787) in Fortinet FortiOS 6.4 through 7.6.3 and FortiSwitchManager 7.0 through 7.2.6 lets an unauthenticated…KEVEPSS 3.9%analysed7.8CVE-2026-53362Linux kernel IPv6 UDP paged allocation out-of-bounds write__ip6_append_data() in the Linux kernel mis-accounts fraggap on the paged-allocation path, leaving the linear skb area undersized while pagedlen is o…KEVEPSS 0.71%analysed7.8CVE-2022-0995Linux kernel watch_queue out-of-bounds writeThe Linux kernel's watch_queue event notification subsystem contains an out-of-bounds write (CWE-787) that can overwrite kernel state. A local user c…KEVEPSS 8.8%analysed8.8CVE-2026-11645Google Chrome V8 out-of-bounds read and write enables sandbox code executionGoogle Chrome before 149.0.7827.103 contains an out-of-bounds read and write in the V8 JavaScript engine. A crafted HTML page can trigger the memory …KEVEPSS 2.2%analysed

Source: NIST National Vulnerability Database (record CVE-2021-33913), CISA KEV, FIRST EPSS (scores of 2026-09-27). This page is refreshed as NVD updates the record.