Red Hat Enterprise Linux up to 10 SoupServer request smuggling

Summaryinfo

A vulnerability, which was classified as problematic, has been found in Red Hat Enterprise Linux 6/7/8/9/10. Impacted is an unknown function of the component SoupServer. Performing a manipulation results in request smuggling. This vulnerability is cataloged as CVE-2026-103399. It is possible to initiate the attack remotely. There is no exploit available.

Detailsinfo

A vulnerability, which was classified as problematic, was found in Red Hat Enterprise Linux 6/7/8/9/10. This affects an unknown functionality of the component SoupServer. The manipulation with an unknown input leads to a request smuggling vulnerability. CWE is classifying the issue as CWE-444. The product acts as an intermediary HTTP agent (such as a proxy or firewall) in the data flow between two entities such as a client and server, but it does not interpret malformed HTTP requests or responses in ways that are consistent with how the messages will be processed by those entities that are at the ultimate destination. This is going to have an impact on integrity. The summary by CVE is:

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.

The advisory is shared at access.redhat.com. This vulnerability is uniquely identified as CVE-2026-103399 since 09/30/2026. The exploitability is told to be easy. It is possible to initiate the attack remotely. No form of authentication is needed for exploitation. Neither technical details nor an exploit are publicly available. The price for an exploit might be around USD $5k-$25k at the moment (estimation calculated on 09/30/2026).

There is no information about possible countermeasures known. It may be suggested to replace the affected object with an alternative product.

Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

Productinfo

Type

• Operating System

Vendor

• Red Hat

Name

• Enterprise Linux

Version

• 6
• 7
• 8
• 9
• 10

License

• commercial

Website

• Vendor: https://www.redhat.com/

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Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

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