CVE-2026-54789
Description
A flaw was found in mod_auth_openidc, an OpenID Connect Relying Party module for Apache HTTP servers. A remote attacker can exploit this vulnerability by sending a specially crafted HTTP request with a malformed state cookie. This can lead to an out-of-bounds read and a one-byte out-of-bounds write during state cookie parsing, primarily resulting in a Denial of Service (DoS) for the affected server.
Statement
This is an Important denial of service flaw in mod_auth_openidc. The vulnerability arises from an out-of-bounds read and write in the state-cookie parser when processing specially crafted Cookie headers. Exploitation could lead to service unavailability for systems configured with mod_auth_openidc for OpenID Connect Relying Party functionality.
Mitigation
Inspect incoming HTTP requests using a Web Application Firewall (WAF), reverse proxy, or Apache’s mod_rewrite module prior to evaluation by mod_auth_openidc. Configure security rules to reject or drop any requests containing malformed Cookie headers—specifically OpenID Connect state cookie tokens that lack an equals sign (=).
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).
The following CVSS metrics and score provided are preliminary and subject to review.
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)
Confidentiality
Technical Impact: Read Memory
An attacker could get secret values such as cryptographic keys, PII, memory addresses, or other information that could be used in additional attacks.
Confidentiality
Technical Impact: Bypass Protection Mechanism
Out-of-bounds memory could contain memory addresses or other information that can be used to bypass ASLR and other protection mechanisms in order to improve the reliability of exploiting a separate weakness for code execution.
Availability
Technical Impact: DoS: Crash, Exit, or Restart
An attacker could cause a segmentation fault or crash by causing memory to be read outside of the bounds of the buffer. This is especially likely when the code reads a variable amount of data and assumes that a sentinel exists to stop the read operation, such as a NUL in a string.
Other
Technical Impact: Varies by Context
The read operation could produce other undefined or unexpected results.
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