CVE-2026-33523

MEDIUMNVD 6.56.5—
EchelonGraph scoreMEDIUM confidence

Score 6.5 from GitHub Security Advisory published 2026-05-04. NVD baseline CVSS 6.5; sources differ by 0.0.

Triggered by: GitHub Security Advisory CVSS
Sources: epss, ghsa, nvd
Trending — 4 sources updated this week
6.5EG
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • Lower severity and no public exploit yet
CISA-KEV: Not listedEPSS PROB: 0%CVSS: 6.5Exploit: None knownExposed: 0

A fix is available — apply it.

HTTP response splitting vulnerability in multiple Apache HTTP Server modules with untrusted or compromised backend servers.

This issue affects Apache HTTP Server: from through 2.4.66.

Users are recommended to upgrade to version 2.4.67, which fixes the issue.

CVSS v3
6.5
EG Score
6.5(medium)
EG Risk
44(Track)
EG Risk 44/100SSVC: 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
Severity65% × 45%
Exploitation0% × 40%
Automatability100% × 15%
Action: Routine — remediate on your standard cadence.
EPSS PROB
0%
EPSS %ILE
36%
KEV
Not listed

Published

May 4, 2026

Last Modified

May 4, 2026

Advisory Details (2)

Auto-updated May 4, 2026
⚠️ Active exploitation confirmed. Patch available.
generic

oss-security - CVE-2026-33523: Apache HTTP Server: multiple modules: HTTP response splitting forwarding malicious status line

http://www.openwall.com/lists/oss-security/2026/05/04/23
generic Patch Available🔴 Active Exploitation

Apache HTTP Server 2.4 vulnerabilities - The Apache HTTP Server Project

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

Vendor Advisories for CVE-2026-33523(2)

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

Patch Availability(3)

Vendor / EcosystemFixed in / PatchReleasedSource
ubuntuapache2-utils (2.4.66-2ubuntu2.1) @ resolute2026-08-23ubuntu
ubuntuapache2-utils (2.4.18-2ubuntu3.17+esm19) @ xenial2026-08-23ubuntu
redhathttpd-main-2.4.67-1.hum12026-05-13redhat

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

(9 across 9 ecosystems)
Alpine:v3.20(1)
PackageVulnerable rangeFixed inDependents
apache2—2.4.67-r0—
Alpine:v3.21(1)
PackageVulnerable rangeFixed inDependents
apache2—2.4.67-r0—
Alpine:v3.22(1)
PackageVulnerable rangeFixed inDependents
apache2—2.4.67-r0—
Alpine:v3.23(1)
PackageVulnerable rangeFixed inDependents
apache2—2.4.67-r0—
Alpine:v3.24(1)
PackageVulnerable rangeFixed inDependents
apache2—2.4.67-r0—
Debian:11(1)
PackageVulnerable rangeFixed inDependents
apache22.4.48-3.1 ... 2.4.66-8 (82 versions)2.4.67-1~deb11u1—
Debian:12(1)
PackageVulnerable rangeFixed inDependents
apache22.4.57-2 ... 2.4.67-1~deb12u1 (46 versions)2.4.67-1~deb12u2—
Debian:13(1)
PackageVulnerable rangeFixed inDependents
apache22.4.65-2 ... 2.4.67-1~deb13u1 (22 versions)2.4.67-1~deb13u2—
Debian:14(1)
PackageVulnerable rangeFixed inDependents
apache22.4.65-2 ... 2.4.67-1~deb13u3 (24 versions)2.4.67-1—

Weakness Classification(1)

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

Additional Vendor Advisories

(2)

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 10× in last 7d / 66× 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 197 total refreshes for this CVE.

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

Frequently asked(5)

What is CVE-2026-33523?
CVE-2026-33523 is a medium vulnerability published on May 4, 2026. HTTP response splitting vulnerability in multiple Apache HTTP Server modules with untrusted or compromised backend servers. This issue affects Apache HTTP Server: from through 2.4.66. Users are recommended to upgrade to version 2.4.67, which fixes the issue.
When was CVE-2026-33523 disclosed?
CVE-2026-33523 was first published in the National Vulnerability Database on May 4, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2026-33523 actively exploited?
CVE-2026-33523 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 0% probability of exploitation in the next 30 days, which ranks it in the top 63.8% of all scored CVEs.
What is the CVSS score of CVE-2026-33523?
CVE-2026-33523 has a CVSS v3 base score of 6.5 (NVD).
How do I remediate CVE-2026-33523?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-33523, 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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