# CVE-2021-33913: libspf2: libspf2 before 1.2.11 has a heap-based buffer overflow that might allow remote attackers to execute arbitrary code (v...

CVE-2021-33913 is fixed in 4 products on 1 platform, first by libmail-spf-xs-perl 1.2.10-7ubuntu0.18.04.1~esm1, released January 19, 2022. It is not reported as exploited. Patch Radar priority: Urgent.

- Web page: https://patchblox.com/security/cve/CVE-2021-33913
- Priority: Urgent
- CVSS: 9.8 (critical)
- EPSS: 0.0964
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Jan 19, 2022

## 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.

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | libmail-spf-xs-perl Ubuntu 18.04.6 LTS (bionic) | 1.2.10-7ubuntu0.18.04.1~esm1 | [libmail-spf-xs-perl 1.2.10-7ubuntu0.18.04.1~esm1](https://patchblox.com/security/data/fix/linux/ubuntu-bionic-libmail-spf-xs-perl-1.2.10-7ubuntu0.18.04.1-esm1.md) | Jan 19, 2022 |
| Linux | libmail-spf-xs-perl Ubuntu 20.04 LTS (focal) | 1.2.10-7+deb9u2build0.20.04.1 | [libmail-spf-xs-perl 1.2.10-7+deb9u2build0.20.04.1](https://patchblox.com/security/data/fix/linux/ubuntu-focal-libmail-spf-xs-perl-1.2.10-7-deb9u2build0.20.04.1.md) | Jan 19, 2022 |
| Linux | libspf2 Debian 12.15 (bookworm) | 1.2.10-7.1 | [DEBIAN-CVE-2021-33913](https://patchblox.com/security/data/fix/linux/debian-cve-2021-33913.md) | Jan 19, 2022 |
| Linux | libspf2 Debian 13.5 (trixie) | 1.2.10-7.1 | [DEBIAN-CVE-2021-33913](https://patchblox.com/security/data/fix/linux/debian-cve-2021-33913.md) | Jan 19, 2022 |
| Linux | libspf2 Debian 14 | 1.2.10-7.1 | [DEBIAN-CVE-2021-33913](https://patchblox.com/security/data/fix/linux/debian-cve-2021-33913.md) | Jan 19, 2022 |
| Linux | libspf2-2 Ubuntu 18.04.6 LTS (bionic) | 1.2.10-7ubuntu0.18.04.1~esm1 | [libspf2-2 1.2.10-7ubuntu0.18.04.1~esm1](https://patchblox.com/security/data/fix/linux/ubuntu-bionic-libspf2-2-1.2.10-7ubuntu0.18.04.1-esm1.md) | Jan 19, 2022 |
| Linux | libspf2-2 Ubuntu 20.04 LTS (focal) | 1.2.10-7+deb9u2build0.20.04.1 | [libspf2-2 1.2.10-7+deb9u2build0.20.04.1](https://patchblox.com/security/data/fix/linux/ubuntu-focal-libspf2-2-1.2.10-7-deb9u2build0.20.04.1.md) | Jan 19, 2022 |
| Linux | spfquery Ubuntu 18.04.6 LTS (bionic) | 1.2.10-7ubuntu0.18.04.1~esm1 | [spfquery 1.2.10-7ubuntu0.18.04.1~esm1](https://patchblox.com/security/data/fix/linux/ubuntu-bionic-spfquery-1.2.10-7ubuntu0.18.04.1-esm1.md) | Jan 19, 2022 |
| Linux | spfquery Ubuntu 20.04 LTS (focal) | 1.2.10-7+deb9u2build0.20.04.1 | [spfquery 1.2.10-7+deb9u2build0.20.04.1](https://patchblox.com/security/data/fix/linux/ubuntu-focal-spfquery-1.2.10-7-deb9u2build0.20.04.1.md) | Jan 19, 2022 |

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Data as of 2026-11-08T19:12:23Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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