CVE-2026-34355
Description
A vulnerability has been identified in the Apache HTTP Server. If the server is configured to connect to a malicious or compromised backend server, an attacker could exploit this flaw to bypass security controls or run unauthorized code on the system.
Statement
This Important vulnerability in mod_proxy_html within the Apache HTTP Server allows an untrusted backend to trigger a buffer overflow. This could lead to a security bypass or arbitrary code execution, posing a significant risk in environments where httpd is configured with untrusted backend services.
Mitigation
Disable the `mod_proxy_html` module if it is not essential for your Apache HTTP Server configuration. If `mod_proxy_html` is required, restrict its use to trusted backend servers only, employing network segmentation and access controls. After modifying the configuration, reload the httpd service for changes to apply, which may cause a brief service interruption.
Steps to disable:
Open /etc/httpd/conf.modules.d/00-proxy.conf.
Add a # to comment out the line: LoadModule proxy_html_module modules/mod_proxy_html.so
Verify configuration syntax: apachectl configtest
Apply the change gracefully: systemctl reload httpd
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 | 7.5 | N/A | 7.5 |
| 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 | None | N/A | None |
| Integrity Impact | None | N/A | None |
| Availability Impact | High | N/A | High |
Vector
Red Hat: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
cve.org: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Understanding the Weakness (CWE)
Integrity,Confidentiality,Availability
Technical Impact: Modify Memory; Execute Unauthorized Code or Commands
Buffer overflows often can be used to execute arbitrary code, which is usually outside the scope of the product's implicit security policy. This can often be used to subvert any other security service.
Availability
Technical Impact: Modify Memory; DoS: Crash, Exit, or Restart; DoS: Resource Consumption (CPU)
Buffer overflows generally lead to crashes. Other attacks leading to lack of availability are possible, including putting the product into an infinite loop.
Frequently Asked Questions
Not sure what something means? Check out our Security Glossary.
Want to get errata notifications? Sign up here.
