CVE-2021-33913
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…
Does this matter?
High impact if exploited, but EPSS currently rates exploitation as unlikely (9.64%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit.
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
- 9.8 CRITICALCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- EPSS
- 9.64% probability · 95th percentile
- Public exploits
- None in Exploit-DB
- CISA KEV
- Not listed
- Weakness
- CWE-787
- Affected
- libspf2 project/libspf2
- Source
- cve@mitre.org
EPSS 9.6% since 26 October 2026; no change recorded yet. The dashed line is the ten per cent mark our analysts treat as “patch before the next change window”. Points are recorded when the score first appears and whenever it moves by a percentage point or more.
References
- https://github.com/shevek/libspf2/tree/8131fe140704eaae695e76b5cd09e39bd1dd220bThird Party Advisory
- https://lists.debian.org/debian-lts-announce/2022/01/msg00015.htmlMailing List, Third Party Advisory
- https://nathanielbennett.com/blog/libspf2-cve-jan-2022-disclosureExploit, Third Party Advisory
- https://security.gentoo.org/glsa/202401-22
- https://github.com/shevek/libspf2/tree/8131fe140704eaae695e76b5cd09e39bd1dd220bThird Party Advisory
- https://lists.debian.org/debian-lts-announce/2022/01/msg00015.htmlMailing List, Third Party Advisory
- https://nathanielbennett.com/blog/libspf2-cve-jan-2022-disclosureExploit, Third Party Advisory
- https://security.gentoo.org/glsa/202401-22
Source: NVD record, EPSS from FIRST.org, KEV from CISA, exploits from Exploit-DB. Refreshed daily. Download this record as JSON.