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.
Affected products
gnome: libsoup; redhat: enterprise linux
References2
- access.redhat.com/security/cve/CVE-2026-66338 Vendor Advisory
- bugzilla.redhat.com/show_bug.cgi?id=2506950 ExploitIssue TrackingVendor Advisory
Metrics
- CVSS 3.1
-
7.2
HIGH
Score source: NVD
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:N - EPSS — exploit probability
- 0% percentile: 22 · as of 14 November 2026
- CWE
- CWE-444
Could this be exploited in your environment?
A patch closes the known hole. A penetration test shows what an attacker can still reach — with proof.