Symfony/Http-Kernel is the HTTP kernel component for Symfony, a PHP framework for web and console applications and a set of reusable PHP components. Headers that are not part of the trusted_headers allowed list are ignored and protect users from Cache poisoning attacks. In Symfony 5.2, maintainers added support for the X-Forwarded-Prefix headers, but this header was accessible in SubRequest, even if it was not part of the trusted_headers allowed list. An attacker could leverage this opportunity to forge requests containing a X-Forwarded-Prefix header, leading to a web cache poisoning issue. Versions 5.3.12 and later have a patch to ensure that the X-Forwarded-Prefix header is not forwarded to subrequests when it is not trusted.
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.
| Name | Vendor | Start Version | End Version |
|---|---|---|---|
| Symfony | Sensiolabs | 5.2.0 (including) | 5.3.12 (excluding) |
| Symfony | Ubuntu | devel | * |
| Symfony | Ubuntu | esm-apps/jammy | * |
| Symfony | Ubuntu | esm-apps/noble | * |
| Symfony | Ubuntu | hirsute | * |
| Symfony | Ubuntu | impish | * |
| Symfony | Ubuntu | jammy | * |
| Symfony | Ubuntu | kinetic | * |
| Symfony | Ubuntu | lunar | * |
| Symfony | Ubuntu | mantic | * |
| Symfony | Ubuntu | noble | * |
| Symfony | Ubuntu | oracular | * |
| Symfony | Ubuntu | trusty | * |
| Symfony | Ubuntu | xenial | * |
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.