CVE-2026-33523: apache software foundation apache http server DEPRECATED: HTTP response splitting
CVSS: 6.5v3.1MediumAnalyzed
AliasesALPINE-CVE-2026-33523UBUNTU-CVE-2026-33523DEBIAN-CVE-2026-33523
Published 04-05-2026Last modified 04-05-2026
Vulnerability summary
CVE-2026-33523 is a medium (CVSS 6.5) DEPRECATED: HTTP response splitting vulnerability in apache software foundation apache http server. EPSS estimates a 0.44% chance of exploitation in the next 30 days, higher than 36.4% of scored vulnerabilities.
CVSS score
6.5/10
010
Medium · v3.1 (CVE.org)EPSS score
0.44%
0%100%
Low · 0.00 pp in 30 daysKEVNot listedIn no KEV catalog
RansomwareNone recordedNo known use recorded
Public exploits0No public exploits recorded
Advisory lineage
Upstream 0 · Downstream 10 · Related 8Timeline
- 04-05-2026PublishedVulnerability first disclosed.
- 04-05-2026Last modifiedVulnerability information updated.
Description
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 metrics
5 scores · 5 sources · 1 versionMedium 6.5Preferred score · CVE.org (CNA)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:NSourcesAll 5 agree
- OSV · AlpineEcosystem advisory · calculated6.5MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N
- OSV · UbuntuEcosystem advisory · calculated6.5MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N
- OSV · DebianEcosystem advisory · calculated6.5MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N
- NVDNIST6.5MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N
EPSS trend
Probability
0.44%
Chance of exploitation in the next 30 days
Percentile
36%
Versus all other CVEs
30-day change
0.00 pp
From 0.44% on 18-09-2026
18-09-202618-10-2026
EPSS score0.44%
Known exploited
Compare KEV catalogsNot in any of the 3 tracked catalogs.
Public exploits
0 foundNo public exploits indexed.
Weaknesses
CWE · root causeAffected systems
Alpine1 product
- apache2< 2.4.67-r0
Apache1 product
- http_server≥ 2.4.0, < 2.4.67
Apache software foundation1 product
- apache http server≥ 2.4.0, ≤ 2.4.66
Debian1 product
- apache2< 2.4.67-1~deb12u2 | < 2.4.67-1~deb13u2 | < 2.4.67-1
Ubuntu1 product
- apache2< 2.4.7-1ubuntu4.22+esm14 | < 2.4.18-2ubuntu3.17+esm19 | < 2.4.29-1ubuntu4.27+esm10 | < 2.4.41-4ubuntu3.23+esm5 | < 2.4.52-1ubuntu4.20 | < 2.4.58-1ubuntu8.12 | < 2.4.64-1ubuntu3.4 | < 2.4.66-2ubuntu2.1
5 vendors · 5 products
References
9 links- httpd.apache.org/security/vulnerabilities_24.htmlVendor Advisory
