Bug 2506950 (CVE-2026-66338) - CVE-2026-66338 libsoup: libsoup: HTTP Request Smuggling via permissive chunk-size parsing in soup_body_input_stream_read_chunked()
Summary: CVE-2026-66338 libsoup: libsoup: HTTP Request Smuggling via permissive chunk-...
Keywords:
Status: NEW
Alias: CVE-2026-66338
Product: Security Response
Classification: Other
Component: vulnerability
Version: unspecified
Hardware: All
OS: Linux
low
low
Target Milestone: ---
Assignee: Product Security DevOps Team
QA Contact:
URL:
Whiteboard:
Depends On:
Blocks:
TreeView+ depends on / blocked
 
Reported: 2026-07-24 22:29 UTC by OSIDB Bzimport
Modified: 2026-07-24 22:56 UTC (History)
2 users (show)

Fixed In Version:
Clone Of:
Environment:
Last Closed:
Embargoed:

Attachments (Terms of Use)

Description OSIDB Bzimport 2026-07-24 22:29:40 UTC 
The chunked transfer encoding parser in libsoup uses strtoul(metabuf, NULL, 16) to parse chunk sizes without strict validation. This function silently accepts inputs that violate RFC 9112 §7.1, including leading whitespace, + prefixes, and trailing invalid characters (e.g., 0z parses as 0). When libsoup operates behind a strict frontend proxy, this parsing differential enables an attacker to smuggle HTTP requests through the backend connection. Both server-side (SoupServer) and client-side chunked response parsing are affected. This is distinct from CVE-2026-1801 which covers bare LF tolerance.

Upstream report: https://gitlab.gnome.org/GNOME/libsoup/-/work_items/533
PSIRTSUPT: https://redhat.atlassian.net/browse/PSIRTSUPT-17666
Note You need to log in before you can comment on or make changes to this bug.