CVE-2026-33523
Description
A flaw was found in httpd. When processing responses from an untrusted or compromised backend server, multiple modules fail to sanitize Carriage Return and Line Feed (CRLF) sequences in the HTTP status line. This issue leads to an HTTP response splitting attack.
Statement
To exploit this vulnerability, the Apache HTTP Server must be configured to connect to an untrusted or compromised backend server, limiting its exposure. Due to this reason, this flaw has been rated with a moderate severity.
Mitigation
To mitigate this issue, ensure that Apache HTTP Server (httpd) is configured to proxy only to trusted backend services. Implement robust network segmentation and access controls to restrict unauthorized access to backend servers. If proxying to potentially untrusted backends is necessary, consider deploying a Web Application Firewall (WAF) or an additional content inspection layer to filter malicious response headers.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 6.5 | N/A | 6.5 |
| Attack Vector | Network | N/A | Network |
| Attack Complexity | Low | N/A | Low |
| Privileges Required | None | N/A | None |
| User Interaction | None | N/A | None |
| Scope | Unchanged | N/A | Unchanged |
| Confidentiality | Low | N/A | Low |
| Integrity Impact | Low | N/A | Low |
| Availability Impact | None | N/A | None |
Vector
Red Hat: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N
cve.org: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N
Understanding the Weakness (CWE)
Integrity
Technical Impact: Modify Application Data
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