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.

Last checked: 2026-09-30 21:40 UTC

• No exploitation evidence · CISA Coordinator (Assessed 2026-09-30 19:10 UTC)

References

• NVD: CVE-2026-103399
• Upstream Advisory