Reference page — cumulative record through Sunday, October 4, 2026 UTC. Reference pages update as the archive grows; only dated daily editions are immutable pages of record.

CVE-2026-66338

CVE-2026-66338HIGH

Red Hat Red Hat Enterprise Linux 10 — Libsoup: libsoup: http request smuggling via permissive chunk-size parsing in soup_body_input_stream_read_chunked()

  AV  AC  PR  UI  S  C  I  A   CVSS    EPSS   %ile   KEV
   N   L   N   N  C  L  L  N    7.2   .0028   18.3     —

AFFECTED
  Product                      Versions     Fixed
  Red Hat Enterprise Linux 10  unspecified  —
  Red Hat Enterprise Linux 6   unspecified  —
  Red Hat Enterprise Linux 7   unspecified  —
  Red Hat Enterprise Linux 8   unspecified  —
  Red Hat Enterprise Linux 9   unspecified  —

TIMELINE
  Jul 24  Reserved by redhat
  Jul 24  Published (CNA: redhat)
  Aug 24  EXPLOIT PUBLISHED — CVE-2026-66338 (Red Hat Enterprise Linux 10). Public exploit reference added.
  Aug 24  RESCORED — CVE-2026-66338 (Red Hat Enterprise Linux 10). CVSS 5.4 → 7.2 (NVD).

CWE-444 · CNA: redhat · CVSS v3.1 · 2 references · NVD status: Analyzed

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.

Lifecycle

Complete event history — 4 events, chronological
Date	Event	Detail
July 24, 2026	Reserved	Reserved by redhat
July 24, 2026	Published	Published (CNA: redhat)
August 24, 2026	EXPLOIT PUBLISHED	EXPLOIT PUBLISHED — CVE-2026-66338 (Red Hat Enterprise Linux 10). Public exploit reference added.
August 24, 2026	RESCORED	RESCORED — CVE-2026-66338 (Red Hat Enterprise Linux 10). CVSS 5.4 → 7.2 (NVD).

Affected

Affected products and packages — 5 rows
Vendor	Product / Package	Ecosystem	Version introduced	Fixed
Red Hat	Red Hat Enterprise Linux 10	—	—	—
Red Hat	Red Hat Enterprise Linux 6	—	—	—
Red Hat	Red Hat Enterprise Linux 7	—	—	—
Red Hat	Red Hat Enterprise Linux 8	—	—	—
Red Hat	Red Hat Enterprise Linux 9	—	—	—

Weaknesses

CWE-444

References (2)

https://access.redhat.com/security/cve/CVE-2026-66338 [Vendor Advisory]
https://bugzilla.redhat.com/show_bug.cgi?id=2506950 [Exploit, Issue Tracking, Vendor Advisory]

Authoritative record: CVE-2026-66338 at cve.org

Vendors: red hat

Weaknesses: CWE-444

About this page

This is a reference page, not a dated page of record. It assembles the complete lifecycle of CVE-2026-66338 from the CVE Program record, NVD enrichment, the CISA KEV catalog, EPSS, and OSV advisories. The box score's numbers (CVSS, EPSS, KEV status) are current as of Sunday, October 4, 2026 UTC and are re-derived as the archive grows; only dated daily editions are immutable pages of record. The authoritative source for this identifier is cve.org.