Apache HTTP Server up to 2.4.66 Module response splitting

CVSS Meta Temp Score
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Current Exploit Price (≈)
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CTI Interest Score
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7.0$5k-$25k0.00

Summaryinfo

A vulnerability categorized as critical has been discovered in Apache HTTP Server up to 2.4.66. Impacted is an unknown function of the component Module. Executing a manipulation can lead to response splitting. This vulnerability is registered as CVE-2026-33523. It is possible to launch the attack remotely. No exploit is available. It is advisable to upgrade the affected component.

Detailsinfo

A vulnerability was found in Apache HTTP Server up to 2.4.66. It has been declared as critical. This vulnerability affects an unknown functionality of the component Module. The manipulation with an unknown input leads to a response splitting vulnerability. The CWE definition for the vulnerability is CWE-443. This weakness can be found at CWE-113. As an impact it is known to affect confidentiality, integrity, and availability. CVE summarizes:

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.

The weakness was published by Haruki Oyama. The advisory is available at httpd.apache.org. This vulnerability was named CVE-2026-33523 since 03/20/2026. The exploitation appears to be easy. The attack can be initiated remotely. No form of authentication is required for a successful exploitation. The technical details are unknown and an exploit is not available. The structure of the vulnerability defines a possible price range of USD $5k-$25k at the moment (estimation calculated on 05/13/2026).

The vulnerability scanner Nessus provides a plugin with the ID 312249 (FreeBSD : www/apache24 -- Multiple vulnerabilities (1ccc383b-486a-11f1-8b62-8447094a420f)), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 2.4.67 eliminates this vulnerability.

The vulnerability is also documented in the databases at Tenable (312249), EUVD (EUVD-2026-26965) and CERT Bund (WID-SEC-2026-1354). If you want to get best quality of vulnerability data, you may have to visit VulDB.

Affected

  • Debian Linux
  • Red Hat Enterprise Linux
  • Fedora Linux
  • Ubuntu Linux
  • IBM HTTP Server
  • Microsoft Azure Linux
  • Apache HTTP Server

Productinfo

Type

Vendor

Name

Version

License

Website

CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 7.3
VulDB Meta Temp Score: 7.0

VulDB Base Score: 7.3
VulDB Temp Score: 7.0
VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv2info

AVACAuCIA
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💳💳💳💳💳💳
💳💳💳💳💳💳
VectorComplexityAuthenticationConfidentialityIntegrityAvailability
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VulDB Base Score: 🔒
VulDB Temp Score: 🔒
VulDB Reliability: 🔍

Exploitinginfo

Class: Response splitting
CWE: CWE-443 / CWE-436
CAPEC: 🔒
ATT&CK: 🔒

Physical: No
Local: No
Remote: Yes

Availability: 🔒
Status: Not defined

EPSS Score: 🔒
EPSS Percentile: 🔒

Price Prediction: 🔍
Current Price Estimation: 🔒

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Nessus ID: 312249
Nessus Name: FreeBSD : www/apache24 -- Multiple vulnerabilities (1ccc383b-486a-11f1-8b62-8447094a420f)

Threat Intelligenceinfo

Interest: 🔍
Active Actors: 🔍
Active APT Groups: 🔍

Countermeasuresinfo

Recommended: Upgrade
Status: 🔍

0-Day Time: 🔒

Upgrade: HTTP Server 2.4.67

Timelineinfo

03/20/2026 CVE reserved
05/04/2026 +44 days Advisory disclosed
05/04/2026 +0 days VulDB entry created
05/13/2026 +9 days VulDB entry last update

Sourcesinfo

Vendor: apache.org

Advisory: httpd.apache.org
Researcher: Haruki Oyama
Status: Confirmed

CVE: CVE-2026-33523 (🔒)
GCVE (CVE): GCVE-0-2026-33523
GCVE (VulDB): GCVE-100-360970
EUVD: 🔒
CERT Bund: WID-SEC-2026-1354 - Apache HTTP Server: Mehrere Schwachstellen

Entryinfo

Created: 05/04/2026 17:23
Updated: 05/13/2026 12:13
Changes: 05/04/2026 17:23 (56), 05/04/2026 19:52 (1), 05/05/2026 12:16 (7), 05/06/2026 04:31 (2), 05/13/2026 12:13 (1)
Complete: 🔍
Cache ID: 216::103

If you want to get best quality of vulnerability data, you may have to visit VulDB.

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