Executive brief
tiny-http is a lightweight library used by developers to build web servers. A security flaw allows attackers to manipulate the technical headers sent between the server and the user. This could be used to trick web browsers into performing unintended actions, such as stealing user sessions, bypassing security settings, or poisoning web caches to serve malicious content to other users.
Technical details
A CRLF injection vulnerability (CWE-113) exists in tiny-http through version 0.12.0 due to insufficient validation of header values during parsing and serialization. An unauthenticated remote attacker can inject 0x0D (CR) and 0x0A (LF) bytes into both request and response headers. This primitive can be leveraged to perform HTTP response splitting, cache poisoning, session fixation via Set-Cookie injection, and request smuggling against backends that are tolerant of line-feed characters. The vulnerability affects both the client-facing and backend-facing sides of the library's header handling.
Affected products
- tiny-http tiny-http through 0.12.0
Timeline
- 2026-07-28: disclosed
- 2026-07-28: advisory