CVE-2026-124739: BusyBox httpd stack buffer overflow in subdirectory config

CVE-2026-124739 · Severity: high · CVSS 7.5 · Published 2026-11-11

BusyBox is a lightweight utility suite often embedded in network devices and IoT systems, including its built-in httpd web server. When processing configuration files in subdirectories, an attacker with write access can craft an overly long index page name to cause a stack overflow, leading to arbitrary code execution with root privileges or a crash of the web server. This vulnerability allows local escalation of privilege if the service runs with elevated permissions.

Technologies: Busybox. Vendors: Busybox.

Quick answers

Is CVE-2026-124739 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-124739 being exploited in the wild.
How severe is CVE-2026-124739?
High severity, with a CVSS score of 7.5, published 11 November 2026.
Which products and versions are affected?
BusyBox BusyBox.
Is there a fix for CVE-2026-124739?
No fixed version is recorded yet. Restrict write permissions on web root and subdirectory paths to administrative accounts only (chmod -R o-w /path/to/webroot). Ensure BusyBox httpd runs as an unprivileged user by using the `-u` flag (e.g., `busybox httpd -u nobody`) and restart the service for the change to take effect. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.
How is CVE-2026-124739 attacked?
It is attacked over the network or with local access, in a network appliance.
Am I affected by CVE-2026-124739?
Check whether you run Busybox. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

How to fix

Restrict write permissions on web root and subdirectory paths to administrative accounts only (chmod -R o-w /path/to/webroot). Ensure BusyBox httpd runs as an unprivileged user by using the `-u` flag (e.g., `busybox httpd -u nobody`) and restart the service for the change to take effect.

Technical details

A stack-based buffer overflow (CWE-787) exists in BusyBox httpd when parsing the "I:" rule in subdirectory httpd.conf configuration files with an overly long index page name. The vulnerability requires network access to a running httpd service and low privileges (local write access to a web-accessible directory or its configuration files), with no user interaction needed. Exploitation allows arbitrary code execution with the service's privilege level or denial of service via process crash.

Affected products

  • BusyBox BusyBox

Timeline

  • 2026-11-11: disclosed

References

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