CVE-2021-44224

CRITICALNVD 8.29.0▲
EchelonGraph scoreHIGH confidence

Score elevated to 9.0 because EPSS predicts 82% probability of exploitation within the next 30 days (top 0.4% of all CVEs). NVD baseline CVSS 8.2 retained for reference. Confidence: see factors.

Triggered by: EPSS exploit prediction ≥85%
Sources: epss, ghsa, nvd
Elevated
9.0EG
EchelonGraph verdictPatch this weekExploitation is likely or a public exploit exists.
  • 2,575 internet-exposed hosts are running an affected version right now
  • High exploitation likelihood — EPSS 82%
CISA-KEV: Not listedEPSS PROB: 82%CVSS: 8.2Exploit: Elevated riskExposed: 2,575

A fix is available — apply it.

A crafted URI sent to httpd configured as a forward proxy (ProxyRequests on) can cause a crash (NULL pointer dereference) or, for configurations mixing forward and reverse proxy declarations, can allow for requests to be directed to a declared Unix Domain Socket endpoint (Server Side Request Forgery). This issue affects Apache HTTP Server 2.4.7 up to 2.4.51 (included).

Live · internet exposure

2,575 internet-exposed hosts are running an affected version of CVE-2021-44224 right now.

across 91 countries (United States, Germany, Japan, France, United Kingdom)top: http_server
See the live KEV-Exposure radar →Found passively from public internet-scan data — aggregate, host-redacted.

EchelonGraph is the only CVE feed that fuses live vulnerability intelligence with its own live internet-exposure radar — so you see not just that a CVE is exploited, but how much of the internet is exposed to it right now.

CVSS v3
8.2
EG Score
9.0(high)
EG Risk
78(Track)
EG Risk 78/100SSVC: 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
Severity90% × 45%
Exploitation82% × 40%
Automatability30% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
82%
EPSS %ILE
100%
KEV
Not listed

Published

December 20, 2021

Last Modified

November 21, 2024

Advisory Details (10)

Auto-updated Sep 9, 2026
⚠️ Active exploitation confirmed. Patch available.
generic

Apache HTTPD: Multiple Vulnerabilities (GLSA 202208-20) — Gentoo security

https://security.gentoo.org/glsa/202208-20
generic

[SECURITY] Fedora 34 Update: httpd-2.4.53-1.fc34 - package-announce - Fedora mailing-lists

https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/Z7H26WJ6TPKNWV3QKY4BHKUKQVUTZJTD/
generic

[SECURITY] Fedora 36 Update: httpd-2.4.53-1.fc36 - package-announce - Fedora mailing-lists

https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/X73C35MMMZGBVPQQCH7LQZUMYZNQA5FO/
generic

[SECURITY] Fedora 35 Update: httpd-2.4.53-1.fc35 - package-announce - Fedora mailing-lists

https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/RGWILBORT67SHMSLYSQZG2NMXGCMPUZO/
generic

[SECURITY] Fedora 35 Update: httpd-2.4.52-1.fc35 - package-announce - Fedora mailing-lists

https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/BFSWOH4X77CV7AH7C4RMHUBDWKQDL4YH/
generic

oss-security - CVE-2021-44224: Apache HTTP Server: Possible NULL dereference or SSRF in forward proxy configurations in Apache HTTP Server 2.4.51 and earlier

http://www.openwall.com/lists/oss-security/2021/12/20/3
generic

Full Disclosure: APPLE-SA-2022-05-16-2 macOS Monterey 12.4

http://seclists.org/fulldisclosure/2022/May/38
generic🔴 Active Exploitation

Full Disclosure: APPLE-SA-2022-05-16-3 macOS Big Sur 11.6.6

http://seclists.org/fulldisclosure/2022/May/35
generic

Full Disclosure: APPLE-SA-2022-05-16-4 Security Update 2022-004 Catalina

http://seclists.org/fulldisclosure/2022/May/33
generic Patch Available🔴 Active Exploitation

Apache HTTP Server 2.4 vulnerabilities - The Apache HTTP Server Project

http://httpd.apache.org/security/vulnerabilities_24.html

Vendor Advisories for CVE-2021-44224(2)

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

Patch Availability(6)

Vendor / EcosystemFixed in / PatchReleasedSource
ubuntuapache2-bin (2.4.48-3.1ubuntu3.2) @ impish2026-05-26ubuntu
ubuntuapache2-utils (2.4.18-2ubuntu3.17+esm4) @ xenial2026-05-26ubuntu
redhatjbcs-httpd24-httpd2022-10-26redhat
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.

Affected Packages

(19 across 19 ecosystems)
Alpine:v3.12(1)
PackageVulnerable rangeFixed inDependents
apache2—2.4.52-r0—
Alpine:v3.13(1)
PackageVulnerable rangeFixed inDependents
apache2—2.4.52-r0—
Alpine:v3.14(1)
PackageVulnerable rangeFixed inDependents
apache2—2.4.52-r0—
Alpine:v3.15(1)
PackageVulnerable rangeFixed inDependents
apache2—2.4.52-r0—
Alpine:v3.16(1)
PackageVulnerable rangeFixed inDependents
apache2—2.4.52-r0—
Alpine:v3.17(1)
PackageVulnerable rangeFixed inDependents
apache2—2.4.52-r0—
Alpine:v3.18(1)
PackageVulnerable rangeFixed inDependents
apache2—2.4.52-r0—
Alpine:v3.19(1)
PackageVulnerable rangeFixed inDependents
apache2—2.4.52-r0—
Alpine:v3.20(1)
PackageVulnerable rangeFixed inDependents
apache2—2.4.52-r0—
Alpine:v3.21(1)
PackageVulnerable rangeFixed inDependents
apache2—2.4.52-r0—
Alpine:v3.22(1)
PackageVulnerable rangeFixed inDependents
apache2—2.4.52-r0—
Alpine:v3.23(1)
PackageVulnerable rangeFixed inDependents
apache2—2.4.52-r0—
Alpine:v3.24(1)
PackageVulnerable rangeFixed inDependents
apache2—2.4.52-r0—
Debian:10(1)
PackageVulnerable rangeFixed inDependents
apache22.4.38-3 ... 2.4.38-3+deb10u6 (7 versions)2.4.38-3+deb10u7—
Debian:11(1)
PackageVulnerable rangeFixed inDependents
apache22.4.48-3.1 ... 2.4.52-1~deb11u1 (20 versions)2.4.52-1~deb11u2—
Debian:12(1)
PackageVulnerable rangeFixed inDependents
apache2—2.4.52-1—
Debian:13(1)
PackageVulnerable rangeFixed inDependents
apache2—2.4.52-1—
Debian:14(1)
PackageVulnerable rangeFixed inDependents
apache2—2.4.52-1—
Debian:9(1)
PackageVulnerable rangeFixed inDependents
apache22.4.25-3 ... 2.4.25-3+deb9u9 (12 versions)2.4.25-3+deb9u12—

Weakness Classification(1)

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

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 3× in last 7d / 15× 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 101 total refreshes for this CVE.

  1. 2026-09-18 19:23 UTCEPSS rescore
  2. 2026-09-16 14:05 UTCEPSS rescore
  3. 2026-09-12 14:57 UTCEPSS rescore
  4. 2026-09-06 13:45 UTCEPSS rescore
  5. 2026-09-06 01:30 UTCOSV refresh
  6. 2026-09-05 15:25 UTCEPSS rescore
  7. 2026-09-04 05:03 UTCEPSS rescore
  8. 2026-08-30 19:14 UTCEPSS rescore
  9. 2026-08-30 19:14 UTCEPSS rescore
  10. 2026-08-30 01:19 UTCEPSS rescore
  11. 2026-08-28 21:37 UTCEPSS rescore
  12. 2026-08-26 14:43 UTCEPSS rescore
  13. 2026-08-24 14:13 UTCEPSS rescore
  14. 2026-08-20 22:52 UTCEPSS rescore
  15. 2026-08-20 22:52 UTCEPSS rescore
  16. 2026-08-19 17:01 UTCEPSS rescore
  17. 2026-08-19 12:59 UTCOSV refresh
  18. 2026-08-16 02:11 UTCEPSS rescore
  19. 2026-08-15 01:27 UTCEPSS rescore
  20. 2026-08-12 13:48 UTCEPSS rescore
  21. 2026-08-06 13:44 UTCEPSS rescore
  22. 2026-08-04 08:27 UTCOSV refresh
  23. 2026-07-28 15:33 UTCEPSS rescore
  24. 2026-07-26 14:52 UTCEPSS rescore
  25. 2026-07-26 14:52 UTCEPSS rescore
Show 75 more
  1. 2026-07-24 14:15 UTCEPSS rescore
  2. 2026-07-23 02:05 UTCEG score recompute▲ 0.80
  3. 2026-07-22 22:51 UTCEG score recompute
  4. 2026-07-22 14:06 UTCEPSS rescore
  5. 2026-07-21 15:22 UTCEPSS rescore
  6. 2026-07-21 15:22 UTCEPSS rescore
  7. 2026-07-20 17:05 UTCEPSS rescore
  8. 2026-07-19 02:27 UTCEPSS rescore
  9. 2026-07-18 05:29 UTCOSV refresh
  10. 2026-07-15 16:55 UTCEPSS rescore
  11. 2026-07-15 16:55 UTCEPSS rescore
  12. 2026-07-13 22:27 UTCEPSS rescore
  13. 2026-07-13 22:27 UTCEPSS rescore
  14. 2026-07-09 19:07 UTCEPSS rescore
  15. 2026-07-06 16:25 UTCEPSS rescore
  16. 2026-07-06 16:25 UTCEPSS rescore
  17. 2026-07-04 06:29 UTCEPSS rescore
  18. 2026-07-04 06:29 UTCEPSS rescore
  19. 2026-07-01 15:04 UTCEPSS rescore
  20. 2026-06-30 01:30 UTCOSV refresh
  21. 2026-06-28 04:54 UTCEPSS rescore
  22. 2026-06-28 04:54 UTCEPSS rescore
  23. 2026-06-25 13:48 UTCEPSS rescore
  24. 2026-06-25 13:48 UTCEPSS rescore
  25. 2026-06-23 21:31 UTCEPSS rescore
  26. 2026-06-23 21:31 UTCEPSS rescore
  27. 2026-06-21 01:58 UTCEPSS rescore
  28. 2026-06-21 01:58 UTCEPSS rescore
  29. 2026-06-17 17:51 UTCEPSS rescore
  30. 2026-06-17 17:51 UTCEPSS rescore
  31. 2026-06-17 17:51 UTCEPSS rescore
  32. 2026-06-15 17:46 UTCEPSS rescore
  33. 2026-06-14 23:15 UTCEPSS rescore
  34. 2026-06-14 23:15 UTCEPSS rescore
  35. 2026-06-13 22:58 UTCEPSS rescore
  36. 2026-06-13 22:58 UTCEPSS rescore
  37. 2026-06-12 23:10 UTCEPSS rescore
  38. 2026-06-12 14:40 UTCOSV refresh
  39. 2026-06-11 13:58 UTCEPSS rescore
  40. 2026-06-11 13:58 UTCEPSS rescore
  41. 2026-06-10 22:16 UTCEPSS rescore
  42. 2026-06-10 22:16 UTCEPSS rescore
  43. 2026-06-10 13:20 UTCEPSS rescore
  44. 2026-06-08 14:15 UTCEPSS rescore
  45. 2026-06-08 14:15 UTCEPSS rescore
  46. 2026-06-07 15:23 UTCEPSS rescore
  47. 2026-06-07 15:23 UTCEPSS rescore
  48. 2026-06-06 13:46 UTCEPSS rescore
  49. 2026-06-06 13:46 UTCEPSS rescore
  50. 2026-06-05 22:45 UTCEPSS rescore
  51. 2026-06-05 06:09 UTCEPSS rescore
  52. 2026-06-05 06:09 UTCEPSS rescore
  53. 2026-06-04 13:10 UTCEPSS rescore
  54. 2026-06-04 13:10 UTCEPSS rescore
  55. 2026-06-02 20:11 UTCEPSS rescore
  56. 2026-06-02 20:11 UTCEPSS rescore
  57. 2026-06-01 13:50 UTCEPSS rescore
  58. 2026-06-01 13:50 UTCEPSS rescore
  59. 2026-05-31 22:29 UTCEPSS rescore
  60. 2026-05-31 22:29 UTCEPSS rescore
  61. 2026-05-31 00:15 UTCEPSS rescore
  62. 2026-05-31 00:15 UTCEPSS rescore
  63. 2026-05-29 13:42 UTCEPSS rescore
  64. 2026-05-28 13:43 UTCEPSS rescore
  65. 2026-05-28 13:43 UTCEPSS rescore
  66. 2026-05-27 13:39 UTCEPSS rescore
  67. 2026-05-27 13:39 UTCEPSS rescore
  68. 2026-05-26 13:42 UTCEPSS rescore
  69. 2026-05-26 13:42 UTCEPSS rescore
  70. 2026-05-26 07:17 UTCEPSS rescore
  71. 2026-05-26 07:17 UTCEPSS rescore
  72. 2026-05-26 07:17 UTCEPSS rescore
  73. 2026-05-26 06:05 UTCEG score recompute
  74. 2026-05-26 06:05 UTCVendor advisory
  75. 2026-05-26 06:05 UTCGHSA enrichment

Frequently asked(5)

What is CVE-2021-44224?
CVE-2021-44224 is a critical vulnerability published on December 20, 2021. A crafted URI sent to httpd configured as a forward proxy (ProxyRequests on) can cause a crash (NULL pointer dereference) or, for configurations mixing forward and reverse proxy declarations, can allow for requests to be directed to a declared Unix Domain Socket endpoint (Server Side Request…
When was CVE-2021-44224 disclosed?
CVE-2021-44224 was first published in the National Vulnerability Database on December 20, 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-2021-44224 actively exploited?
CVE-2021-44224 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 82% probability of exploitation in the next 30 days, which ranks it in the top 0.4% of all scored CVEs.
What is the CVSS score of CVE-2021-44224?
CVE-2021-44224 has a CVSS v3 base score of 8.2 (NVD). EchelonGraph synthesises NVD + CISA KEV + FIRST EPSS + GHSA into a combined EG score of 9.0.
How do I remediate CVE-2021-44224?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2021-44224, 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-2021-44224

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