VULNERABILITY INTELLIGENCE

CVE-2026-66338

CVSS score5.4 MEDIUM
EPSS probability0.29%
CISA KEVNot currently listed
Published2026-07-24
Last modified2026-08-24
CVSS vectorCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:L/I:L/A:N

Description

A flaw was found in libsoup. The chunked transfer encoding parser uses a permissive parsing function for chunk sizes that silently accepts inputs violating RFC 9112, including leading whitespace, plus sign prefixes, and trailing invalid characters. When libsoup operates behind a strict frontend proxy, this parsing differential can be exploited to smuggle HTTP requests.

Weakness classification

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

Primary references