HTTP Request Smuggling Vulnerability in Libsoup by Red Hat
CVE-2026-66338

5.4MEDIUM

Key Information:

Vendor

Red Hat
Status
Red Hat Enterprise Linux 10
Red Hat Enterprise Linux 6
Red Hat Enterprise Linux 7
Red Hat Enterprise Linux 8
Vendor
CVE Published:
24 July 2026

What is CVE-2026-66338?

A vulnerability exists in libsoup's chunked transfer encoding parser, which employs a lenient parsing technique that overlooks inputs that breach RFC 9112 standards. This flaw enables the acceptance of leading whitespace, plus sign prefixes, and trailing invalid characters in chunk sizes. When libsoup is used in conjunction with a strict frontend proxy, this inconsistency can be exploited, allowing attackers to smuggle malicious HTTP requests, potentially compromising the integrity and security of web applications.

References

https://access.redhat.com/security/cve/CVE-2026-66338
vdb-entryx_refsource_REDHAT
https://bugzilla.redhat.com/show_bug.cgi?id=2506950
issue-trackingx_refsource_REDHAT

CVSS V3.1

Score:
5.4
Severity:
MEDIUM
Confidentiality:
Low
Integrity:
Low
Availability:
Low
Attack Vector:
Network
Attack Complexity:
High
Privileges Required:
None
User Interaction:
None
Scope:
Changed

Timeline

  • Vulnerability published

  • Vulnerability Reserved

Credit

Upstream acknowledges cavid as the original reporter.
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