CVE-2026-34356
Description
A flaw was found in Apache HTTP Server. This heap-based buffer overflow vulnerability can be exploited by a malicious backend server when using ProxyPassReverseCookie* directives. This could lead to a denial of service (DoS) condition, making the server unavailable to legitimate users.
Statement
This flaw in Apache could allow a malicious backend server to crash your web server, making it unavailable to users. Your system is only at risk if you use Apache to forward traffic to untrusted or unverified backend systems.
Mitigation
To prevent this denial-of-service flaw, ensure your Apache proxy rules only connect to highly trusted backend servers. If you must proxy traffic to unverified or external backends, disable the cookie-rewriting features.
Steps to Mitigate:
Open your Apache configuration file (e.g., /etc/httpd/conf/httpd.conf).
Locate and comment out any ProxyPassReverseCookieDomain or ProxyPassReverseCookiePath lines pointing to untrusted backends by adding a # at the start of the line.
Test your syntax: apachectl configtest
Apply changes gracefully: systemctl reload httpd
Note: This may cause a brief service interruption.
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
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