Is there a public exploit for CVE-2026-103399?

No public exploit for CVE-2026-103399 was found in Exploit-DB, Metasploit, Nuclei templates or public proof-of-concept repositories. That is an absence of evidence rather than proof that none exists.

How severe is CVE-2026-103399?

CVE-2026-103399 scores CVSS 5.3 (v3.1), rated medium. EPSS puts the chance of exploitation in the next 30 days at 0.25%.

5.3 Medium

A flaw was found in SoupServer (libsoup).

CVE-2026-103399

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.

Assessment

CVSS: 5.3 (v3.1)
Severity: Medium
EPSS: 0.25% chance of exploitation in the next 30 days
Known exploited: Not listed in CISA KEV
Exploit availability: Nothing found in Exploit-DB, Metasploit, Nuclei or public PoC repositories
Published: 30 September 2026
Last updated: 3 November 2026
Assigner: redhat

CVSS vectorCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N

At the source

EUVD (ENISA)

References

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