CVE-2021-33193

HIGHNVD 7.57.9▲
EchelonGraph scoreHIGH confidence

Score elevated to 7.9 because EPSS predicts 46% probability of exploitation within the next 30 days (top 1.3% of all CVEs). NVD baseline CVSS 7.5 retained for reference. Confidence: see factors.

Triggered by: EPSS exploit prediction ≥85%
Sources: epss, ghsa, nvd
Trending — 3 sources updated this weekElevated
7.5
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS: 46%CVSS: 7.5Exploit: NoneExposed: 0

A fix is available — apply it.

A crafted method sent through HTTP/2 will bypass validation and be forwarded by mod_proxy, which can lead to request splitting or cache poisoning. This issue affects Apache HTTP Server 2.4.17 to 2.4.48.

CVSS v3
7.5
EG Score
7.9(high)
EG Risk
59(Track)
EG Risk 59/100SSVC: 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
Severity79% × 45%
Exploitation46% × 40%
Automatability30% × 15%
Action: Routine — remediate on your standard cadence.
EPSS
98.7%
KEV
Not listed

Published

August 16, 2021

Last Modified

May 1, 2025

References (26)

Vendor Advisories for CVE-2021-33193(1)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Patch Availability(5)

Vendor / EcosystemFixed in / PatchReleasedSource
ubuntuapache2-bin (2.4.46-4ubuntu1.2) @ hirsute2026-05-26ubuntu
redhathttpd2022-10-26redhat
redhatjbcs-httpd24-httpd-0:2.4.51-28.el7jbcs2022-10-26redhat
redhathttpd24-httpd-0:2.4.34-23.el7.52022-09-29redhat
redhathttpd:2.4-8060020220321163517.d63f516d2022-05-10redhat

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.

Additional Vendor Advisories

(5)

Vendors that published advisories for this CVE beyond the curated set above. Broader coverage but minimal per-row detail — click through for the original advisory.

Data Freshness Timeline

(refreshed 9× in last 7d / 31× 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. 2026-07-23 02:01 UTCEG score recompute▲ 0.40
  2. 2026-07-22 22:48 UTCEG score recompute
  3. 2026-07-22 14:06 UTCEPSS rescore
  4. 2026-07-22 14:06 UTCEPSS rescore
  5. 2026-07-20 17:05 UTCEPSS rescore
  6. 2026-07-19 02:27 UTCEPSS rescore
  7. 2026-07-18 14:29 UTCOSV refresh
  8. 2026-07-18 10:02 UTCEPSS rescore
  9. 2026-07-18 10:02 UTCEPSS rescore
  10. 2026-07-15 16:55 UTCEPSS rescore
  11. 2026-07-13 22:27 UTCEPSS rescore
  12. 2026-07-13 06:10 UTCEPSS rescore
  13. 2026-07-12 05:44 UTCEPSS rescore
  14. 2026-07-12 05:44 UTCEPSS rescore
  15. 2026-07-11 08:25 UTCEPSS rescore
  16. 2026-07-11 08:25 UTCEPSS rescore
  17. 2026-07-09 19:07 UTCEPSS rescore
  18. 2026-07-05 02:28 UTCEPSS rescore
  19. 2026-07-05 02:28 UTCEPSS rescore
  20. 2026-07-01 15:04 UTCEPSS rescore
  21. 2026-06-30 19:00 UTCOSV refresh
  22. 2026-06-29 14:04 UTCEPSS rescore
  23. 2026-06-28 04:54 UTCEPSS rescore
  24. 2026-06-28 04:54 UTCEPSS rescore
  25. 2026-06-27 03:06 UTCEPSS rescore
Show 57 more
  1. 2026-06-25 13:48 UTCEPSS rescore
  2. 2026-06-25 13:48 UTCEPSS rescore
  3. 2026-06-24 14:03 UTCEPSS rescore
  4. 2026-06-24 14:03 UTCEPSS rescore
  5. 2026-06-23 21:31 UTCEPSS rescore
  6. 2026-06-23 21:31 UTCEPSS rescore
  7. 2026-06-21 01:58 UTCEPSS rescore
  8. 2026-06-21 01:58 UTCEPSS rescore
  9. 2026-06-18 17:51 UTCEPSS rescore
  10. 2026-06-18 17:51 UTCEPSS rescore
  11. 2026-06-17 17:51 UTCEPSS rescore
  12. 2026-06-16 17:51 UTCEPSS rescore
  13. 2026-06-16 17:51 UTCEPSS rescore
  14. 2026-06-15 17:46 UTCEPSS rescore
  15. 2026-06-14 23:15 UTCEPSS rescore
  16. 2026-06-13 22:58 UTCEPSS rescore
  17. 2026-06-13 22:58 UTCEPSS rescore
  18. 2026-06-13 00:14 UTCOSV refresh
  19. 2026-06-12 23:10 UTCEPSS rescore
  20. 2026-06-12 23:10 UTCEPSS rescore
  21. 2026-06-11 13:58 UTCEPSS rescore
  22. 2026-06-10 22:16 UTCEPSS rescore
  23. 2026-06-10 13:20 UTCEPSS rescore
  24. 2026-06-08 14:15 UTCEPSS rescore
  25. 2026-06-08 14:15 UTCEPSS rescore
  26. 2026-06-07 15:23 UTCEPSS rescore
  27. 2026-06-07 15:23 UTCEPSS rescore
  28. 2026-06-06 13:46 UTCEPSS rescore
  29. 2026-06-06 13:46 UTCEPSS rescore
  30. 2026-06-06 13:46 UTCEPSS rescore
  31. 2026-06-05 22:45 UTCEPSS rescore
  32. 2026-06-05 06:09 UTCEPSS rescore
  33. 2026-06-05 06:09 UTCEPSS rescore
  34. 2026-06-04 13:10 UTCEPSS rescore
  35. 2026-06-04 13:10 UTCEPSS rescore
  36. 2026-06-02 20:11 UTCEPSS rescore
  37. 2026-06-02 20:11 UTCEPSS rescore
  38. 2026-06-01 13:50 UTCEPSS rescore
  39. 2026-06-01 13:50 UTCEPSS rescore
  40. 2026-05-31 22:29 UTCEPSS rescore
  41. 2026-05-31 22:29 UTCEPSS rescore
  42. 2026-05-31 00:15 UTCEPSS rescore
  43. 2026-05-31 00:15 UTCEPSS rescore
  44. 2026-05-29 13:42 UTCEPSS rescore
  45. 2026-05-29 13:42 UTCEPSS rescore
  46. 2026-05-28 13:43 UTCEPSS rescore
  47. 2026-05-28 13:43 UTCEPSS rescore
  48. 2026-05-27 13:39 UTCEPSS rescore
  49. 2026-05-27 13:39 UTCEPSS rescore
  50. 2026-05-27 13:39 UTCEPSS rescore
  51. 2026-05-26 13:42 UTCEPSS rescore
  52. 2026-05-26 12:01 UTCEG score recompute
  53. 2026-05-26 12:01 UTCVendor advisory
  54. 2026-05-26 12:01 UTCGHSA enrichment
  55. 2026-05-26 07:17 UTCEPSS rescore
  56. 2026-05-26 07:17 UTCEPSS rescore
  57. 2026-05-26 07:17 UTCEPSS rescore

Related CVEs(same vendor)

Frequently asked(5)

What is CVE-2021-33193?
CVE-2021-33193 is a high vulnerability published on August 16, 2021. A crafted method sent through HTTP/2 will bypass validation and be forwarded by mod_proxy, which can lead to request splitting or cache poisoning. This issue affects Apache HTTP Server 2.4.17 to 2.4.48.
When was CVE-2021-33193 disclosed?
CVE-2021-33193 was first published in the National Vulnerability Database on August 16, 2021, with the most recent update on May 1, 2025. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2021-33193 actively exploited?
CVE-2021-33193 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 98.7% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2021-33193?
CVE-2021-33193 has a CVSS v3 base score of 7.5 (NVD). EchelonGraph synthesises NVD + CISA KEV + FIRST EPSS + GHSA into a combined EG score of 7.9.
How do I remediate CVE-2021-33193?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2021-33193, 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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