Bug 2552119

Summary: CVE-2026-88829 busybox: busybox: HTTP request smuggling via pipelined requests in httpd reverse proxy [fedora-all]
Product: [Fedora] Fedora Reporter: lcelant
Component: busyboxAssignee: Tom "spot" Callaway <spotrh>
Status: NEW --- QA Contact: Fedora Extras Quality Assurance <extras-qa>
Severity: medium Docs Contact:
Priority: medium    
Version: rawhideCC: admiller, davide, dvlasenk, epel-packagers-sig, spotrh, suraj.ghimire7
Target Milestone: ---Keywords: Security, SecurityTracking
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Hardware: Unspecified   
OS: Unspecified   
Whiteboard: {"flaws": ["159fff16-71ba-4189-a080-3aa9f3282681"]}
Fixed In Version: Doc Type: ---
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oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
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Bug Depends On:    
Bug Blocks: 2531343    

Description lcelant 2026-10-14 08:44:25 UTC 
Disclaimer: Community trackers are created by Red Hat Product Security team on a best effort basis. Package maintainers are required to ascertain if the flaw indeed affects their package, before starting the update process.

BusyBox httpd reverse proxy (CONFIG_FEATURE_HTTPD_PROXY, default enabled). When a P: rule matches, handle_incoming_and_exit() in networking/httpd.c rewrites only the first request line to the backend path (lines 2458-2462), sets G.POST_len = INT_MAX (line 2467), and enters cgi_io_loop_and_exit() (line 2468), which relays further client bytes to the backend without HTTP parsing. A pipelined second request on the same TCP connection therefore reaches the backend at an attacker-chosen path and method, bypassing the P: prefix boundary. This is distinct from Basic auth on proxied URLs: upstream documents that proxying is done without password checks (comment near line 76); maintainer Denys Vlasenko (22 Sep 2026) confirmed that framing as an auth bypass is intended. The pipelining/path-boundary issue was not addressed upstream. Introduced with verbatim proxy relay (commit c69f64845, 2019); affects 1.31.0 through master. No fix. Fedora enables the proxy feature; Debian does not. Independent verification: Kaiden Opus 2026-10-14 (reject-dispute run) confirms smuggling; withdraws auth-bypass as CVE scope. Reported by Shubham Raj, Causal Security (https://causalsecurity.com).