CVE-2021-33913

CRITICALNVD 9.89.8—
EchelonGraph scoreMEDIUM confidence

Score 9.8 from GitHub Security Advisory (severity: CRITICAL) published 2022-01-20. NVD baseline CVSS 9.8; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, nvd
Elevated
9.8EG
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS PROB: 10%CVSS: 9.8Exploit: Elevated riskExposed: 0

A fix is available — apply it.

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 v3
9.8
EG Score
9.8(medium)
EG Risk
52(Track)
EG Risk 52/100SSVC: Track

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity98% × 45%
Exploitation10% × 40%
Automatability30% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
10%
EPSS %ILE
95%
KEV
Not listed

Published

January 19, 2022

Last Modified

November 21, 2024

Advisory Details (3)

Auto-updated Sep 5, 2026
Patch available.
generic

libspf2: Multiple vulnerabilities (GLSA 202401-22) — Gentoo security

https://security.gentoo.org/glsa/202401-22
generic Patch Available

[SECURITY] [DLA 2890-1] libspf2 security update

https://lists.debian.org/debian-lts-announce/2022/01/msg00015.html
generic

GitHub - shevek/libspf2 at 8131fe140704eaae695e76b5cd09e39bd1dd220b · GitHub

https://github.com/shevek/libspf2/tree/8131fe140704eaae695e76b5cd09e39bd1dd220b

Patch Availability(2)

Vendor / EcosystemFixed in / PatchReleasedSource
ubuntuspfquery (1.2.10-6ubuntu0.1~esm2) @ xenial2026-05-26ubuntu
ubuntuspfquery (1.2.10-7ubuntu0.18.04.1~esm1) @ bionic2026-05-26ubuntu

Patches are aggregated from vendor advisories (Red Hat, Microsoft, Cisco, GitHub) and package ecosystems (OSV, GHSA). Multiple rows for the same upstream release have been deduplicated.

Affected Packages

(16 across 16 ecosystems)
Alpine:v3.14(1)
PackageVulnerable rangeFixed inDependents
libspf2—1.2.11-r0—
Alpine:v3.15(1)
PackageVulnerable rangeFixed inDependents
libspf2—1.2.11-r0—
Alpine:v3.16(1)
PackageVulnerable rangeFixed inDependents
libspf2—1.2.11-r0—
Alpine:v3.17(1)
PackageVulnerable rangeFixed inDependents
libspf2—1.2.11-r0—
Alpine:v3.18(1)
PackageVulnerable rangeFixed inDependents
libspf2—1.2.11-r0—
Alpine:v3.19(1)
PackageVulnerable rangeFixed inDependents
libspf2—1.2.11-r0—
Alpine:v3.20(1)
PackageVulnerable rangeFixed inDependents
libspf2—1.2.11-r0—
Alpine:v3.21(1)
PackageVulnerable rangeFixed inDependents
libspf2—1.2.11-r0—
Alpine:v3.22(1)
PackageVulnerable rangeFixed inDependents
libspf2—1.2.11-r0—
Alpine:v3.23(1)
PackageVulnerable rangeFixed inDependents
libspf2—1.2.11-r0—
Alpine:v3.24(1)
PackageVulnerable rangeFixed inDependents
libspf2—1.2.11-r0—
Debian:11(1)
PackageVulnerable rangeFixed inDependents
libspf21.2.10-7, 1.2.10-7.1~deb10u11.2.10-7.1~deb11u1—
Debian:12(1)
PackageVulnerable rangeFixed inDependents
libspf2—1.2.10-7.1—
Debian:13(1)
PackageVulnerable rangeFixed inDependents
libspf2—1.2.10-7.1—
Debian:14(1)
PackageVulnerable rangeFixed inDependents
libspf2—1.2.10-7.1—
Debian:9(1)
PackageVulnerable rangeFixed inDependents
libspf21.2.10-7, 1.2.10-7+deb9u11.2.10-7+deb9u2—

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

All Vendor Advisories

(2)

Every vendor that published an advisory referencing this CVE — pulled from our cve_vendor_advisories aggregation. Click any row for the vendor's original advisory page.

Data Freshness Timeline

(refreshed 8× in last 7d / 32× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

Showing the most recent 100 of 154 total refreshes for this CVE.

  1. 2026-09-07 15:58 UTCEPSS rescore
  2. 2026-09-06 13:45 UTCEPSS rescore
  3. 2026-09-06 13:45 UTCEPSS rescore
  4. 2026-09-05 23:21 UTCOSV refresh
  5. 2026-09-05 15:25 UTCEPSS rescore
  6. 2026-09-04 13:57 UTCEPSS rescore
  7. 2026-09-04 05:03 UTCEPSS rescore
  8. 2026-09-02 14:08 UTCEPSS rescore
  9. 2026-09-01 13:50 UTCEPSS rescore
  10. 2026-09-01 03:32 UTCEPSS rescore
  11. 2026-08-30 19:14 UTCEPSS rescore
  12. 2026-08-30 01:19 UTCEPSS rescore
  13. 2026-08-30 01:19 UTCEPSS rescore
  14. 2026-08-28 21:37 UTCEPSS rescore
  15. 2026-08-27 14:22 UTCEPSS rescore
  16. 2026-08-26 14:42 UTCEPSS rescore
  17. 2026-08-25 13:46 UTCEPSS rescore
  18. 2026-08-24 14:13 UTCEPSS rescore
  19. 2026-08-23 00:16 UTCEPSS rescore
  20. 2026-08-21 23:46 UTCEPSS rescore
  21. 2026-08-20 22:52 UTCEPSS rescore
  22. 2026-08-19 17:01 UTCEPSS rescore
  23. 2026-08-19 10:29 UTCOSV refresh
  24. 2026-08-18 13:45 UTCEPSS rescore
  25. 2026-08-17 13:44 UTCEPSS rescore
Show 75 more
  1. 2026-08-16 14:53 UTCEPSS rescore
  2. 2026-08-16 02:11 UTCEPSS rescore
  3. 2026-08-16 02:11 UTCEPSS rescore
  4. 2026-08-15 01:27 UTCEPSS rescore
  5. 2026-08-13 21:57 UTCEPSS rescore
  6. 2026-08-12 13:48 UTCEPSS rescore
  7. 2026-08-11 13:38 UTCEPSS rescore
  8. 2026-08-09 13:44 UTCEPSS rescore
  9. 2026-08-08 16:33 UTCEPSS rescore
  10. 2026-08-07 16:24 UTCEPSS rescore
  11. 2026-08-06 13:43 UTCEPSS rescore
  12. 2026-08-05 19:14 UTCEPSS rescore
  13. 2026-08-04 15:06 UTCEPSS rescore
  14. 2026-08-04 10:34 UTCEPSS rescore
  15. 2026-08-04 06:27 UTCOSV refresh
  16. 2026-08-03 10:33 UTCEPSS rescore
  17. 2026-08-02 02:24 UTCEPSS rescore
  18. 2026-08-02 02:24 UTCEPSS rescore
  19. 2026-08-01 04:13 UTCEPSS rescore
  20. 2026-07-30 16:25 UTCEPSS rescore
  21. 2026-07-30 01:28 UTCEPSS rescore
  22. 2026-07-28 15:33 UTCEPSS rescore
  23. 2026-07-25 14:15 UTCEPSS rescore
  24. 2026-07-24 14:15 UTCEPSS rescore
  25. 2026-07-23 14:16 UTCEPSS rescore
  26. 2026-07-23 14:16 UTCEPSS rescore
  27. 2026-07-23 02:01 UTCEG score recompute
  28. 2026-07-22 22:48 UTCEG score recompute
  29. 2026-07-22 14:06 UTCEPSS rescore
  30. 2026-07-22 14:06 UTCEPSS rescore
  31. 2026-07-21 15:22 UTCEPSS rescore
  32. 2026-07-21 15:22 UTCEPSS rescore
  33. 2026-07-20 17:05 UTCEPSS rescore
  34. 2026-07-19 14:29 UTCEPSS rescore
  35. 2026-07-19 14:29 UTCEPSS rescore
  36. 2026-07-19 02:27 UTCEPSS rescore
  37. 2026-07-18 10:02 UTCEPSS rescore
  38. 2026-07-18 10:02 UTCEPSS rescore
  39. 2026-07-18 03:29 UTCOSV refresh
  40. 2026-07-16 17:00 UTCEPSS rescore
  41. 2026-07-16 17:00 UTCEPSS rescore
  42. 2026-07-15 16:55 UTCEPSS rescore
  43. 2026-07-15 01:58 UTCEPSS rescore
  44. 2026-07-13 22:27 UTCEPSS rescore
  45. 2026-07-13 06:10 UTCEPSS rescore
  46. 2026-07-12 05:44 UTCEPSS rescore
  47. 2026-07-12 05:44 UTCEPSS rescore
  48. 2026-07-11 08:25 UTCEPSS rescore
  49. 2026-07-11 08:25 UTCEPSS rescore
  50. 2026-07-09 19:07 UTCEPSS rescore
  51. 2026-07-08 15:12 UTCEPSS rescore
  52. 2026-07-07 13:43 UTCEPSS rescore
  53. 2026-07-06 16:25 UTCEPSS rescore
  54. 2026-07-06 02:21 UTCEPSS rescore
  55. 2026-07-05 02:28 UTCEPSS rescore
  56. 2026-07-05 02:28 UTCEPSS rescore
  57. 2026-07-04 06:29 UTCEPSS rescore
  58. 2026-07-04 06:29 UTCEPSS rescore
  59. 2026-07-01 15:04 UTCEPSS rescore
  60. 2026-06-30 23:20 UTCEPSS rescore
  61. 2026-06-30 23:20 UTCEPSS rescore
  62. 2026-06-29 22:44 UTCOSV refresh
  63. 2026-06-29 14:04 UTCEPSS rescore
  64. 2026-06-28 14:05 UTCEPSS rescore
  65. 2026-06-28 04:54 UTCEPSS rescore
  66. 2026-06-28 04:54 UTCEPSS rescore
  67. 2026-06-27 03:06 UTCEPSS rescore
  68. 2026-06-25 13:48 UTCEPSS rescore
  69. 2026-06-25 13:48 UTCEPSS rescore
  70. 2026-06-24 14:03 UTCEPSS rescore
  71. 2026-06-24 14:03 UTCEPSS rescore
  72. 2026-06-23 21:31 UTCEPSS rescore
  73. 2026-06-23 21:31 UTCEPSS rescore
  74. 2026-06-22 14:24 UTCEPSS rescore
  75. 2026-06-22 14:24 UTCEPSS rescore

Related CVEs(same vendor + same CWE)

Frequently asked(5)

What is CVE-2021-33913?
CVE-2021-33913 is a critical vulnerability published on January 19, 2022. 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 SPFrecordexpanddata in spfexpand.c. The amount of overflowed data…
When was CVE-2021-33913 disclosed?
CVE-2021-33913 was first published in the National Vulnerability Database on January 19, 2022, with the most recent update on November 21, 2024. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2021-33913 actively exploited?
CVE-2021-33913 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 10% probability of exploitation in the next 30 days, which ranks it in the top 4.8% of all scored CVEs.
What is the CVSS score of CVE-2021-33913?
CVE-2021-33913 has a CVSS v3 base score of 9.8 (NVD).
How do I remediate CVE-2021-33913?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2021-33913, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

Dependency Blast Radius

See which npm, PyPI, Go, and Maven packages are affected by CVE-2021-33913

Explore →

Is Your Infrastructure Affected by CVE-2021-33913?

EchelonGraph automatically scans your cloud infrastructure and maps CVE exposure using blast radius analysis.

Start Free Scan →Browse All CVEs