CVE-2025-6442 Ruby WEBrick read_header HTTP Request Smuggling Vulnerability
Remote attackers can smuggle arbitrary HTTP requests in Ruby WEBrick when deployed behind a specific HTTP proxy, bypassing security controls.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2025-6442?
CVE-2025-6442 is a medium-severity vulnerability in Ruby WEBrick, published on 25 Jun 2025. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
Ruby WEBrick read_header HTTP Request Smuggling Vulnerability. This vulnerability allows remote attackers to smuggle arbitrary HTTP requests on affected installations of Ruby WEBrick. This issue is exploitable when the product is deployed behind an HTTP proxy that fulfills specific conditions.
The specific flaw exists within the read_headers method. The issue results from the inconsistent parsing of terminators of HTTP headers. An attacker can leverage this vulnerability to smuggle arbitrary HTTP requests. Was ZDI-CAN-21876.
Weakness: CWE-444
Which versions are affected by CVE-2025-6442?
2 open source packages ship an affected version, including webrick. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
webrick RubyGems | All versions | 1.8.2 |
webrick RubyGems | All versions | 1.8.2 |
Products include Ruby-Lang Webrick.
How do I fix CVE-2025-6442?
Upgrade webrick to 1.8.2 or later.
Is CVE-2025-6442 being exploited?
There is no known exploitation of CVE-2025-6442 in the wild and no public exploit code.
Other vulnerabilities in Ruby WEBrick
Sources
Also known as AZL-64352, AZL-64355, AZL-64364, AZL-64367, DEBIAN-CVE-2025-6442, GHSA-r995-q44h-hr64 and 3 more.