CVE-2026-124739
Description
A flaw was found in BusyBox. When the httpd web server processes subdirectory configuration files, an overly long index page name can trigger a stack-based buffer overflow. An attacker with permissions to write to a subdirectory configuration file could exploit this vulnerability to execute arbitrary code with elevated privileges or cause a denial of service (DoS) by crashing the server process.
Statement
This vulnerability is rated as Important because successful exploitation allows a local user with write access to web-accessible directories to execute arbitrary code with elevated root privileges or trigger a denial of service. Within Red Hat environments, BusyBox is not deployed as a standard web server by default, significantly limiting exposure in standard installations. Exploitation specifically requires the BusyBox httpd service to be actively running and serving content from directories where untrusted users possess write permissions to introduce or modify local configuration files.
Mitigation
Prevent untrusted users from creating or modifying configuration files by restricting write permissions on all web root and subdirectory paths served by BusyBox httpd to administrative accounts only:
chmod -R o-w /path/to/webroot
Additionally, ensure the BusyBox httpd process drops elevated privileges by specifying an unprivileged user with the `-u` flag upon execution:
busybox httpd -u nobody
Restarting the daemon is required for process-level flag changes to take effect, which will temporarily terminate active network connections.
Caveats: Running under a non-privileged user account prevents binding directly to privileged ports (below 1024) without additional system capabilities or port forwarding, and restricting directory permissions may interfere with workflows that require unprivileged file uploads.
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 | High | N/A | High |
| Privileges Required | Low | N/A | Low |
| User Interaction | None | N/A | None |
| Scope | Unchanged | N/A | Unchanged |
| Confidentiality | High | N/A | High |
| Integrity Impact | High | N/A | High |
| Availability Impact | High | N/A | High |
Vector
Red Hat: CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
cve.org: CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
Understanding the Weakness (CWE)
Integrity
Technical Impact: Modify Memory; Execute Unauthorized Code or Commands
Write operations could cause memory corruption. In some cases, an adversary can modify control data such as return addresses in order to execute unexpected code.
Availability
Technical Impact: DoS: Crash, Exit, or Restart
Attempting to access out-of-range, invalid, or unauthorized memory could cause the product to crash.
Other
Technical Impact: Unexpected State
Subsequent write operations can produce undefined or unexpected results.
Acknowledgements
Red Hat would like to thank ducanhluu for reporting this issue.
Frequently Asked Questions
Not sure what something means? Check out our Security Glossary.
Want to get errata notifications? Sign up here.
