CVE-2017-2666

It was discovered in Undertow that the code that parsed the HTTP request line permitted invalid characters. This could be exploited, in conjunction with a proxy that also permitted the invalid characters but with a different interpretation, to inject data into the HTTP response. By manipulating the HTTP response the attacker could poison a web-cache, perform an XSS attack, or obtain sensitive information from requests other than their own.

Weakness

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.

Affected Software

Extended Description

HTTP requests or responses (“messages”) can be malformed or unexpected in ways that cause web servers or clients to interpret the messages in different ways than intermediary HTTP agents such as load balancers, reverse proxies, web caching proxies, application firewalls, etc. For example, an adversary may be able to add duplicate or different header fields that a client or server might interpret as one set of messages, whereas the intermediary might interpret the same sequence of bytes as a different set of messages. For example, discrepancies can arise in how to handle duplicate headers like two Transfer-encoding (TE) or two Content-length (CL), or the malicious HTTP message will have different headers for TE and CL. The inconsistent parsing and interpretation of messages can allow the adversary to “smuggle” a message to the client/server without the intermediary being aware of it. This weakness is usually the result of the usage of outdated or incompatible HTTP protocol versions in the HTTP agents.

Potential Mitigations

Related Attack Patterns

• https://cwe.mitre.org/data/definitions/273.html
• https://cwe.mitre.org/data/definitions/33.html

References

• http://rhn.redhat.com/errata/RHSA-2017-1409.html
• http://www.securityfocus.com/bid/98966
• https://access.redhat.com/errata/RHSA-2017:1410
• https://access.redhat.com/errata/RHSA-2017:1411
• https://access.redhat.com/errata/RHSA-2017:1412
• https://access.redhat.com/errata/RHSA-2017:3454
• https://access.redhat.com/errata/RHSA-2017:3455
• https://access.redhat.com/errata/RHSA-2017:3456
• https://access.redhat.com/errata/RHSA-2017:3458
• https://bugzilla.redhat.com/show_bug.cgi?id=CVE-2017-2666
• https://www.debian.org/security/2017/dsa-3906