CVE-2026-66338CWE-444

CVE-2026-66338

Medium · published July 25, 2026

CVSS v3.1
5.4
EPSS
0%
Percentile
20.5
In the wild
Unconfirmed
What it is

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.

The record
Technical detail
CVSS v3.1
5.4 · MEDIUM
Vector
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:L/I:L/A:N
CVSS v4.0
Not supplied
EPSS
0.00291 · 20.5th percentile
Weakness
CWE-444 · Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')
Published
2026-07-25T03:16Z
Affected products (6)
ProductVersionsFixed in
gnome/libsoupall versions—
redhat/enterprise_linuxall versions—
redhat/enterprise_linuxall versions—
redhat/enterprise_linuxall versions—
redhat/enterprise_linuxall versions—
redhat/enterprise_linuxall versions—
References (2)
https://access.redhat.com/security/cve/CVE-2026-66338 · [email protected]https://bugzilla.redhat.com/show_bug.cgi?id=2506950 · [email protected]
EPSS history
Timeline
  • 24 JUL 23:01Z
    Libsoup: libsoup: http request smuggling via permissive chunk-size parsing in soup_body_input_stream_read_chunked()
    cvelistv5