CVE-2026-103399
Red Hat Enterprise Linux 10: Libsoup: soupserver: http/1 request smuggling via undrained expect: 100-continue body
Red Hat Red Hat Enterprise Linux 10Operating systems
CVSS
5.3MediumExploitationNo known exploitationNot in CISA KEV, which does not prove it is unexploitedCISA KEV
Exploit odds (EPSS)0.24%Chance of exploitation activity in the next 30 days, higher than 14% of CVEs. Scored 23 Oct 2026FIRST EPSS
Fixed inNone listedNo source names a fixed version. Check the vendor advisory below
What fixes it
No source in this snapshot names a fixed version. The vendor advisories under References are the place to check.
Description
A flaw was found in SoupServer (libsoup). When an HTTP/1.x client sends a request with Expect: 100-continue and a request body, and SoupServer returns an early final (non-1xx) response before the body is read, the server neither drains the declared body bytes nor closes the connection. On a keep-alive connection, those leftover bytes are interpreted as a subsequent HTTP request. A remote, unauthenticated attacker can place a complete HTTP request in the body and cause SoupServer to process that smuggled request, leading to unintended request handling.
Text from CVE List