CVE-2026-88831 Busybox: busybox: httpd silently fails open when ip deny rules contain invalid cidr prefix lengths
Medium 5.3
Published
Updated
Check this codebase for CVE-2026-88831 and fix it if it is affected.
What it is: CVE-2026-88831 is a medium-severity vulnerability in Red Hat Hardened Images, published on 23 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-88831 in the wild and no public exploit code.
Affected product: Red Hat Hardened Images. No package-level version data is available, so check the vendor advisory linked from the reference page.
Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.
Reference: https://insights.sbomify.com/CVE-2026-88831/ (Markdown: https://insights.sbomify.com/CVE-2026-88831/index.md)
BusyBox httpd fails open on invalid CIDR rules, allowing attackers to bypass IP-based access controls.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-88831?
CVE-2026-88831 is a medium-severity vulnerability in Red Hat Hardened Images, published on 23 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
BusyBox httpd IP deny rules with invalid CIDR prefix lengths fail open, leaving a parsed IP with a zeroed mask so the rule matches no clients.
Weakness: CWE-636
Which versions are affected by CVE-2026-88831?
How do I fix CVE-2026-88831?
Apply the vendor's patch.
Is CVE-2026-88831 being exploited?
There is no known exploitation of CVE-2026-88831 in the wild and no public exploit code.
Sources
Also known as AZL-105131, BELL-CVE-2026-88831, DEBIAN-CVE-2026-88831, ECHO-00bb-2927-406e, GHSA-w27x-jw4w-69xf, UBUNTU-CVE-2026-88831.