CVE
Busybox: httpd stack buffer overflow via an "i:" rule in a subdirectory httpd.conf
Affects BusyBox httpd serving directories where untrusted users can write httpd.conf files, as listed for Red Hat Enterprise Linux 6 and Red Hat Hardened Images. No fixed version is listed yet.
Written by anthropic/claude-haiku-5.5 from the sources below. Verify against them.
- Exploited
- No known exploitation
- Fix
- See vendor advisory
- Who is exposed
- Specific setups only
Do first: Check whether your setup matches what the bug needs. BusyBox httpd is running and serving content from directories where untrusted users can write configuration files. httpd parses subdirectory httpd.conf files and honors an index-page rule in them. The overflow is triggered by an overly long index page name in a subdirectory httpd.conf when that directory is requested.
- Last modified
- Whether it needs action now or is a reference record, by fixed rules, with why. Last checked is when cve.now last re-read it.What do these mean? →
- Reference
- Last checked
- A 0-100 score for how much a CVE matters across the industry: exploitation, exposure, how widely the software is used, severity and whether a fix exists.What do these mean? →
- 31/100 · provisional
- How many real-world setups can hit the bug, from the vendor's advisory and CISA data. It does not know your setup.What do these mean? →
- Specific setups only
- Whether working attack code is public (Exploit-DB, Metasploit, Nuclei or GitHub). Public code makes attacks easier.What do these mean? →
- None on Exploit-DB, Metasploit or GitHub
Summary
BusyBox's httpd web server in Red Hat Enterprise Linux 6 and Red Hat Hardened Images has a stack buffer overflow when it processes subdirectory configuration files that contain an overly long index page name. A remote attacker with low-privilege login and write access to a subdirectory configuration file could run arbitrary code with elevated privileges or crash the server.
Read the original 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.
Who should check
Teams running BusyBox httpd on Red Hat Enterprise Linux 6 or Red Hat Hardened Images, especially where web-served directories are writable by untrusted users.
cve.now Index
- Exploitation?/40Unknown. No CISA SSVC exploitation rating yet
- Exposure8/25Specific setups only, reachable over the network
- Reach10/20Shipped in major Linux distributions
- Severity7.5/10CVSS 7.5
- No patch5/5No fixed version listed; see vendor advisory
What would change the score
- Would score about 81 if added to CISA KEV
- Would score about 76 if CISA's SSVC rates exploitation active
- Would score about 38 if CISA's SSVC rates it automatable
What to do
Check whether your setup matches what the bug needs.
BusyBox httpd is running and serving content from directories where untrusted users can write configuration files. httpd parses subdirectory httpd.conf files and honors an index-page rule in them. The overflow is triggered by an overly long index page name in a subdirectory httpd.conf when that directory is requested.Workaround: Restrict write permissions on web root and subdirectory paths to administrative accounts only, and run busybox httpd with -u to drop privileges to an unprivileged user.
Check your systems with an agent
Paste this into a coding or ops agent. It checks your systems read-only and reports a table per asset.
Check whether my systems are affected by CVE-2026-124739 (Busybox: httpd stack buffer overflow via an "i:" rule in a subdirectory httpd.conf), using the cve.now data below.
Rules: work read-only. Do not run exploit code, proof-of-concept scripts or scanners that send attack payloads, and do not change any configuration, package, image or deployment. Report findings only.
What cve.now has for CVE-2026-124739 (entry last updated 2026-11-11):
Affected:
- Red Hat Red Hat Enterprise Linux 6: version range not reported
- Red Hat Red Hat Hardened Images: version range not reported
Fixed versions: none listed yet.
Conditions (all must be true for the bug to be hit):
- BusyBox httpd is running and serving content from directories where untrusted users can write configuration files. (source: https://access.redhat.com/security/cve/cve-2026-124739)
- httpd parses subdirectory httpd.conf files and honors an index-page rule in them. (source: https://bugzilla.redhat.com/show_bug.cgi?id=2571613)
- The overflow is triggered by an overly long index page name in a subdirectory httpd.conf when that directory is requested. (source: https://bugzilla.redhat.com/show_bug.cgi?id=2571613)
Setup: the bug needs a feature or setting that is off by default or uncommon. Check whether each asset has it on.
Attacker needs: network access, low-privilege login, no user action.
Workaround: Restrict write permissions on web root and subdirectory paths to administrative accounts only, and run busybox httpd with -u to drop privileges to an unprivileged user. (source: https://www.cve.org/CVERecord?id=CVE-2026-124739)
CISA KEV: CVE-2026-124739 is not listed as of cve.now's last read.
This KEV status is for CVE-2026-124739 only. If you also check another CVE, look up its own KEV status; never assume it from this one.
How to check:
- Installed software: check what is actually running, not what a repo declares. Read the version from each host, container image and Kubernetes node (the binary's version output, the OS package database, image layers), and check whether the conditions above hold there. Distribution packages may carry a backported fix under an older version number; confirm against the distribution's own advisory.
Verify against the linked advisories before concluding, and cite the date you read each one:
- https://bugzilla.redhat.com/show_bug.cgi?id=2571613
- https://access.redhat.com/security/cve/CVE-2026-124739
- https://www.cve.org/CVERecord?id=CVE-2026-124739
- https://access.redhat.com/security/cve/cve-2026-124739
Do not conclude an asset is unaffected unless you checked it and the evidence covers both its version and the conditions above. If you could not check something, mark it unknown and say what is missing.
Report a table with one row per asset and these columns: Asset | Version or build | Status (affected, fixed, not applicable, unknown) | Compensating controls | Exposure (internet-facing, internal, none) | Evidence | Next action.
Entry: https://cve.now/CVE-2026-124739
For follow-up questions, use the cve.now MCP server at https://mcp.cve.now/mcp (no authentication), for example execute with name cve.get and arguments {"id": "CVE-2026-124739"}.Timeline
- CVE published
- First seen by cve.now
- Record last updated
Affected versions
- busybox
Version range not reported
- busybox
Version range not reported
Evidence 4
CVE record · 2
Establishes: The identifier and description.
- Record
- Record
Write-ups · 1
Establishes: Technical detail and context.
- Report
Other links · 1
- Link
Corrections
None so far.
Something wrong on this page? Report an error. Every fix is listed here.
Questions about CVE-2026-124739
Is CVE-2026-124739 being exploited?
It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. No public exploit code is tracked.Source: cve.now feed data
What does this mean?
An overly long index page name in a subdirectory httpd.conf overflows a stack buffer in BusyBox httpd when that directory is requested. The overflow can lead to arbitrary code execution with elevated root privileges or a crash of the httpd server process.Source: access.redhat.com, bugzilla.redhat.com, cve.org
Am I affected, and how do I check?
The issue applies when BusyBox httpd is running, serves content from directories where untrusted users can write configuration files, and parses subdirectory httpd.conf files that honor an index-page rule. Check whether httpd is running and who can write to its served directories; no affected version range is given in the facts.Source: access.redhat.com, bugzilla.redhat.com, cve.org
How do I fix CVE-2026-124739?
No fixed version is listed in the facts, so no upgrade target can be named. Check the vendor advisory for a fixed BusyBox build and apply it when available.Source: access.redhat.com, bugzilla.redhat.com, cve.org
What if there's no patch?
Restrict write permissions on the web root and its subdirectories to administrative accounts only. Run busybox httpd with the -u option to drop privileges to an unprivileged user.Source: access.redhat.com, bugzilla.redhat.com, cve.org