CVE-2026-73637
Description
A flaw was found in httpd's mod_auth_digest module. A use-after-free vulnerability allows an unauthenticated remote attacker to corrupt the server's authentication state by submitting concurrent Digest authentication requests. This issue occurs when specific configuration settings, such as nonce checking (AuthDigestNcCheck) or zero-duration nonce lifetimes (AuthDigestNonceLifetime), are enabled.
Mitigation
To mitigate this issue, apply one of the following configuration options:
1. Disable `mod_auth_digest` if Digest authentication is not required:
In `/etc/httpd/conf.modules.d/00-base.conf` (or the relevant module configuration file), comment out the loading of the module:
# LoadModule auth_digest_module modules/mod_auth_digest.so
2. If Digest authentication is required, ensure vulnerable settings are disabled:
Ensure `AuthDigestNcCheck` is set to `Off` (or removed, as `Off` is the default) and ensure `AuthDigestNonceLifetime` is not set to `0` (the default value is 300 seconds).
After applying configuration adjustments, reload the web server:
systemctl reload httpd
Warning: Reloading or restarting the `httpd` service may briefly disrupt active client connections. Disabling `mod_auth_digest` will cause authentication failures for resources configured with `AuthType Digest`.
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 | 5.6 | N/A | 7.3 |
| Attack Vector | Network | N/A | Network |
| Attack Complexity | High | 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 | Low | N/A | Low |
Vector
Red Hat: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:L
cve.org: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L
Understanding the Weakness (CWE)
Confidentiality
Technical Impact: Read Memory
If the expired pointer is used in a read operation, an attacker might be able to control data read in by the application.
Availability
Technical Impact: DoS: Crash, Exit, or Restart
If the expired pointer references a memory location that is not accessible to the product, or points to a location that is "malformed" (such as NULL) or larger than expected by a read or write operation, then a crash may occur.
Integrity,Confidentiality,Availability
Technical Impact: Execute Unauthorized Code or Commands
If the expired pointer is used in a function call, or points to unexpected data in a write operation, then code execution may be possible.
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