CVE-2021-22881

MEDIUMNVD 6.19.0▲
EchelonGraph scoreHIGH confidence

Score elevated to 9.0 because EPSS predicts 87% probability of exploitation within the next 30 days (top 0.3% of all CVEs). NVD baseline CVSS 6.1 retained for reference. Confidence: see factors.

Triggered by: EPSS exploit prediction ≥85%
Sources: epss, nvd
Trending — 3 sources updated this weekElevated
6.1
EchelonGraph verdictPatch this weekExploitation is likely or a public exploit exists.
  • High exploitation likelihood — EPSS 87%
CISA-KEV: Not listedEPSS: 87%CVSS: 6.1Exploit: NoneExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

The Host Authorization middleware in Action Pack before 6.1.2.1, 6.0.3.5 suffers from an open redirect vulnerability. Specially crafted Host headers in combination with certain "allowed host" formats can cause the Host Authorization middleware in Action Pack to redirect users to a malicious website. Impacted applications will have allowed hosts with a leading dot. When an allowed host contains a leading dot, a specially crafted Host header can be used to redirect to a malicious website.

CVSS v3
6.1
EG Score
9.0(high)
EPSS
99.7%
KEV
Not listed

Published

February 11, 2021

Last Modified

November 21, 2024

References (14)

Affected Packages

(1 across 1 ecosystem)
RubyGems(1)
PackageVulnerable rangeFixed inDependents
actionpack6.1.0, 6.1.1, 6.1.26.1.2.1—

Weakness Classification(1)

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

Data Freshness Timeline

(refreshed 4× in last 7d / 21× 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.

  1. 2026-07-22 21:28 UTCEG score recompute▲ 2.90
  2. 2026-07-22 14:05 UTCEPSS rescore
  3. 2026-07-20 17:04 UTCEPSS rescore
  4. 2026-07-19 01:59 UTCOSV refresh
  5. 2026-07-15 16:55 UTCEPSS rescore
  6. 2026-07-15 16:55 UTCEPSS rescore
  7. 2026-07-13 22:27 UTCEPSS rescore
  8. 2026-07-13 22:27 UTCEPSS rescore
  9. 2026-07-12 05:44 UTCEPSS rescore
  10. 2026-07-12 05:44 UTCEPSS rescore
  11. 2026-07-11 08:25 UTCEPSS rescore
  12. 2026-07-04 06:29 UTCEPSS rescore
  13. 2026-07-04 06:29 UTCEPSS rescore
  14. 2026-07-01 15:03 UTCEPSS rescore
  15. 2026-07-01 08:48 UTCOSV refresh
  16. 2026-06-27 03:06 UTCEPSS rescore
  17. 2026-06-27 03:06 UTCEPSS rescore
  18. 2026-06-24 14:03 UTCEPSS rescore
  19. 2026-06-24 14:03 UTCEPSS rescore
  20. 2026-06-23 21:31 UTCEPSS rescore
  21. 2026-06-23 21:31 UTCEPSS rescore
  22. 2026-06-19 19:24 UTCEPSS rescore
  23. 2026-06-19 19:24 UTCEPSS rescore
  24. 2026-06-16 17:50 UTCEPSS rescore
  25. 2026-06-15 17:46 UTCEPSS rescore
Show 36 more
  1. 2026-06-14 23:15 UTCEPSS rescore
  2. 2026-06-13 22:58 UTCEPSS rescore
  3. 2026-06-13 14:13 UTCOSV refresh
  4. 2026-06-12 23:10 UTCEPSS rescore
  5. 2026-06-12 23:10 UTCEPSS rescore
  6. 2026-06-11 13:58 UTCEPSS rescore
  7. 2026-06-10 22:16 UTCEPSS rescore
  8. 2026-06-10 22:16 UTCEPSS rescore
  9. 2026-06-10 13:20 UTCEPSS rescore
  10. 2026-06-07 15:23 UTCEPSS rescore
  11. 2026-06-07 15:23 UTCEPSS rescore
  12. 2026-06-06 13:46 UTCEPSS rescore
  13. 2026-06-06 13:46 UTCEPSS rescore
  14. 2026-06-06 13:46 UTCEPSS rescore
  15. 2026-06-05 22:45 UTCEPSS rescore
  16. 2026-06-05 22:45 UTCEPSS rescore
  17. 2026-06-05 06:09 UTCEPSS rescore
  18. 2026-06-05 06:09 UTCEPSS rescore
  19. 2026-06-05 06:08 UTCEPSS rescore
  20. 2026-06-04 13:10 UTCEPSS rescore
  21. 2026-06-02 20:11 UTCEPSS rescore
  22. 2026-06-02 20:11 UTCEPSS rescore
  23. 2026-06-01 13:50 UTCEPSS rescore
  24. 2026-06-01 13:50 UTCEPSS rescore
  25. 2026-05-31 22:29 UTCEPSS rescore
  26. 2026-05-31 22:29 UTCEPSS rescore
  27. 2026-05-31 00:15 UTCEPSS rescore
  28. 2026-05-31 00:15 UTCEPSS rescore
  29. 2026-05-29 13:42 UTCEPSS rescore
  30. 2026-05-28 13:43 UTCEPSS rescore
  31. 2026-05-28 13:43 UTCEPSS rescore
  32. 2026-05-27 13:39 UTCEPSS rescore
  33. 2026-05-26 20:55 UTCEG score recompute
  34. 2026-05-26 13:42 UTCEPSS rescore
  35. 2026-05-26 13:42 UTCEPSS rescore
  36. 2026-05-24 16:49 UTCEPSS rescore

Publicly available exploits

(1 reference)

Working exploit code is in the public domain. Defenders should treat patch urgency accordingly — public PoCs typically lead to mass-exploitation within 24-72 hours.

  • Nucleihttp/cves/2021/CVE-2021-22881.yaml
    First seen Jan 1, 2021

    Ruby on Rails - Open Redirect via Host Header Injection

    Open source ↗

Related CVEs(same CWE)

Frequently asked(5)

What is CVE-2021-22881?
CVE-2021-22881 is a medium vulnerability published on February 11, 2021. The Host Authorization middleware in Action Pack before 6.1.2.1, 6.0.3.5 suffers from an open redirect vulnerability. Specially crafted Host headers in combination with certain "allowed host" formats can cause the Host Authorization middleware in Action Pack to redirect users to a malicious…
When was CVE-2021-22881 disclosed?
CVE-2021-22881 was first published in the National Vulnerability Database on February 11, 2021, 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-2021-22881 actively exploited?
CVE-2021-22881 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 99.7% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2021-22881?
CVE-2021-22881 has a CVSS v3 base score of 6.1 (NVD). EchelonGraph synthesises NVD + CISA KEV + FIRST EPSS + GHSA into a combined EG score of 9.0.
How do I remediate CVE-2021-22881?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2021-22881, 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

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