Critical · published November 4, 2025
⚠️ The trailer fields are slipping into the headers! This medium-severity vulnerability in lighttpd 1.4.80 lets attackers perform HTTP Header Smuggling, causing chaos without breaking a sweat. 🔥 Think of it like a restaurant where the waitstaff accidentally mixes special requests into the main dish — the kitchen might not recognize what’s custom and serve something unsafe instead. In the same way, headers that aren’t properly checked can lead to unauthorized actions behind the scenes! If exploited, an attacker could bypass access control rules and inject unsafe input into backend logic, leading to any unwanted outcomes based on trusted request headers. This could result in unauthorized access to sensitive data or even executing harmful actions that affect users. Yikes!
Think of it like a restaurant where the waitstaff accidentally mixes special requests into the main dish — the kitchen might not recognize what’s custom and serve something unsafe instead. In the same way, headers that aren’t properly checked can lead to unauthorized actions behind the scenes! The vulnerability stems from lighttpd 1.4.80 incorrectly merging trailer fields into headers after parsing the HTTP request. This mishandling allows for HTTP Header Smuggling attacks under certain conditions, compromising the expected behavior of the server.
If exploited, an attacker could bypass access control rules and inject unsafe input into backend logic, leading to any unwanted outcomes based on trusted request headers. This could result in unauthorized access to sensitive data or even executing harmful actions that affect users. Yikes! To safeguard against this issue, update lighttpd to a newer version immediately. Ensure that you audit any code that handles HTTP headers to tighten your security and validate all header inputs properly. Don't wait! You've got this! Fixing this vulnerability will keep your server safe and sound. 🛡️
| Product | Versions | Fixed in |
|---|---|---|
| lighttpd/lighttpd | all versions | — |