CVE 2026 88829

A flaw was found in BusyBox httpd's reverse proxy feature. When the proxy is configured to forward requests matching a URL prefix to a backend server, only the first HTTP request on a TCP connection has its path rewritten. An attacker can send a pipelined second request that is relayed verbatim to the backend, bypassing the configured path restrictions. This allows accessing arbitrary paths on the backend server that were not intended to be exposed through the proxy.

Red Hat product impact analysis is pending. Fedora ships busybox with CONFIG_FEATURE_HTTPD_PROXY enabled and is affected when P: reverse proxy rules are used. RHEL does not ship busybox as a standard package. The flaw applies only where httpd.conf defines P: directives that are meant to limit which backend URL paths are reachable through the proxy. It does not apply to static/CGI-only httpd without proxy rules. BusyBox does not enforce httpd Basic authentication on proxied URLs by design; that behavior is not part of this CVE.

Do not use BusyBox httpd P: rules as the sole path-based access control in front of sensitive backends. Remove P: lines if proxying is not required, or place a full reverse proxy (for example nginx or HAProxy) in front of the backend. Recompile with FEATURE_HTTPD_PROXY disabled if the applet is not needed.

Bugzilla 2531343 : busybox: busybox: HTTP request smuggling via pipelined requests in httpd reverse proxy

CWE-444 : Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')

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: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:N

cve.org: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:N

Red Hat CVSS v3 Score Explanation

Re-scoped 2026-10-14 (Kaiden dispute run): CWE-444 pipelined smuggling past P: prefix only; auth-before-proxy withdrawn as documented intent. S:C for backend as separate authority; C:L/I:L depends on backend exposure.

Understanding the Weakness (CWE)

Integrity,Non-Repudiation,Access Control

Technical Impact: Unexpected State; Hide Activities; Bypass Protection Mechanism

An attacker could create HTTP messages to exploit a number of weaknesses including 1) the message can trick the web server to associate a URL with another URL's webpage and caching the contents of the webpage (web cache poisoning attack), 2) the message can be structured to bypass the firewall protection mechanisms and gain unauthorized access to a web application, and 3) the message can invoke a script or a page that returns client credentials (similar to a Cross Site Scripting attack).

Red Hat would like to thank Shubham Raj (Causal Security) for reporting this issue.

Frequently Asked Questions

"Under investigation" doesn't necessarily mean that the product is affected by this vulnerability. It only means that our Analysis Team is still working on determining whether the product is affected and how it is affected.

The term 'Affected' means that our Analysis team has determined that this product, such as Red Hat Enterprise Linux 8 or OpenShift Container Platform 4, is affected by this vulnerability and a fix may be released to address this issue in the near future. This includes all minor releases of this product unless noted otherwise in the Statement text.

Upgrade to a supported product version that includes a fix for this vulnerability (recommended).

Apply a mitigation (if one exists).

Customers with the Technical Account Manager (TAM) RHEL Security Select Add-on can review this CVE directly with their TAM.

Apply a mitigation (if one exists).

Red Hat Engineering focuses on addressing high-priority issues based on the impact and product lifecycle expectations. Therefore, lower-priority issues will not receive immediate fixes.

Customers with the technical account manager (TAM) RHEL Security Select Add-on can review this CVE directly with their TAM.

Not sure what something means? Check out our Security Glossary .

For clarification or corrections, please Red Hat Product Security .