CVE-2026-66338: Gnome Libsoup

High severity, CVSS 7.2. EPSS: 0.3% chance of exploitation in the next 30 days.

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.

Affected products

• Gnome Libsoup: affected versions not specified
• Red Hat Enterprise Linux: version 6.0 only; version 7.0 only; version 8.0 only; version 9.0 only; version 10.0 only

Published 2026-07-24. Last modified 2026-08-24.