What happened
httpd function check_header/3 rejects duplicate Content-Length (per CVE-2026-23941) but never checks for the TE+CL co-presence that RFC 9112 §6.3 identifies as a probable smuggling attempt. handle_body/3 frames by chunked and silently discards Content-Length. A CL-preferring front-end paired with chunked-preferring inets creates a classic CL.TE front-end/back-end desync. This issue affects OTP from OTP 17.0 before OTP 27.3.4.17, from OTP 28.0 before OTP 28.5.0.6, and from OTP 29.0 before OTP 29.0.6, corresponding to inets from 5.10 before 9.3.2.7, from 9.4 before 9.6.2.3, and from 9.7 before 9.7.2. Whether OTP before OTP 17.0, corresponding to inets before 5.10, is affected is unknown.
Affected versions
OTP: 17.0 through before 27.3.4.17 (otp); 28.0 through before 28.5.0.6 (otp); 29.0 through before 29.0.6 (otp); 5.10 through before 9.3.2.7 (otp); 9.4 through before 9.6.2.3 (otp); 9.7 through before 9.7.2 (otp); 84adefa331c4159d432d22840663c38f155cd4c1 through before 591dc00dc99dc2a426167a3b5257c0c94bd45e91 (git) Fixed: See vendor advisory.
Why it matters
Review the vendor advisory and exposure of the affected product to determine operational impact.
Detection & mitigation
- Apply vendor-provided updates or mitigations.
- Review affected product exposure and access logs.
Public PoC references
No public PoC reference has passed the current publication threshold.