CVE-2025-61780 Rack has Possible Information Disclosure Vulnerability
Attackers can bypass proxy access controls to access protected internal endpoints by crafting specific headers in Rack::Sendfile.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2025-61780?
CVE-2025-61780 is a medium-severity vulnerability in rack, published on 10 Oct 2025. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
Rack is a modular Ruby web server interface. Prior to versions 2.2.20, 3.1.18, and 3.2.3, a possible information disclosure vulnerability existed in `Rack::Sendfile` when running behind a proxy that supports `x-sendfile` headers (such as Nginx). Specially crafted headers could cause `Rack::Sendfile` to miscommunicate with the proxy and trigger unintended internal requests, potentially bypassing proxy-level access restrictions. When `Rack::Sendfile` received untrusted `x-sendfile-type` or `x-accel-mapping` headers from a client, it would interpret them as proxy configuration directives. This could cause the middleware to send a "redirect" response to the proxy, prompting it to reissue a new internal request that was not subject to the proxy's access controls. An attacker could exploit this by setting a crafted `x-sendfile-type: x-accel-redirect` header, setting a crafted `x-accel-mapping` header, and requesting a path that qualifies for proxy-based acceleration. Attackers could bypass proxy-enforced restrictions and access internal endpoints intended to be protected (such as administrative pages). The vulnerability did not allow arbitrary file reads but could expose sensitive application routes. This issue only affected systems meeting all of the following conditions: The application used `Rack::Sendfile` with a proxy that supports `x-accel-redirect` (e.g., Nginx); the proxy did **not** always set or remove the `x-sendfile-type` and `x-accel-mapping` headers; and the application exposed an endpoint that returned a body responding to `.to_path`. Users should upgrade to Rack versions 2.2.20, 3.1.18, or 3.2.3, which require explicit configuration to enable `x-accel-redirect`. Alternatively, configure the proxy to always set or strip the header, or in Rails applications, disable sendfile completely.
Which versions are affected by CVE-2025-61780?
6 open source packages ship an affected version, including rack. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
rack RubyGems | All versions | 2.2.20 |
rack RubyGems | All versions | 2.2.20 |
rack RubyGems | From 3.0 | 3.1.18 |
rack RubyGems | From 3.0 | 3.1.18 |
rack RubyGems | From 3.2 | 3.2.3 |
rack RubyGems | From 3.2 | 3.2.3 |
Products include Rack Rack.
How do I fix CVE-2025-61780?
Upgrade rack to a fixed version for your release line: 2.2.20, 3.1.18 or 3.2.3.
Is CVE-2025-61780 being exploited?
There is no known exploitation of CVE-2025-61780 in the wild and no public exploit code.
Other vulnerabilities in rack
- CVE-2026-34785 Rack: Local file inclusion in `Rack::Static` via URL Prefix Matching
- CVE-2026-34827 Rack: Algorithmic-Complexity DoS in Rack::Multipart::Parser
- CVE-2026-34829 Rack: Denial of Service via Unbounded Multipart File Upload Without Content-Length
- CVE-2026-22860 Rack has a Directory Traversal via Rack:Directory
- CVE-2025-61919 Rack is vulnerable to a memory-exhaustion DoS through unbounded URL-encoded body parsing
Sources
Also known as CLEANSTART-2026-HO19975, DEBIAN-CVE-2025-61780, GHSA-r657-rxjc-j557, MINI-29cw-v24q-q78p, MINI-2qvh-mwcf-7w25, MINI-4fh9-fgp7-9qhq and 12 more.