Cached redirect poisoning via X-Forwarded-Host header

published 2021-06-29 5 y ago modified 2026-07-08 4 mo ago also GHSA-w6rq-6h34-vh7q , EUVD-2021-1496

cvss: 7.0; version 3.1, CNA
cisa kev: Not listed; not in CISA's catalog
epss: 0.9%; EPSS 0.9% chance of exploitation in 30 days, percentile 58%
public exploits: 0; none known

Ratpack is a toolkit for creating web applications. In versions prior to 1.9.0, a user supplied `X-Forwarded-Host` header can be used to perform cache poisoning of a cache fronting a Ratpack server if the cache key does not include the `X-Forwarded-Host` header as a cache key. Users are only vulnerable if they do not configure a custom `PublicAddress` instance. For versions prior to 1.9.0, by default, Ratpack utilizes an inferring version of `PublicAddress` which is vulnerable. This can be used to perform redirect cache poisoning where an attacker can force a cached redirect to redirect to their site instead of the intended redirect location. The vulnerability was patched in Ratpack 1.9.0. As a workaround, ensure that `ServerConfigBuilder::publicAddress` correctly configures the server in production.

Patch / fix

fixed in 2

maven io.ratpack:ratpack-core 1.9.0
ratpack_project ratpack 1.9.0

Exploit prediction

0.86% chance of exploitation in the next 30 days, higher than 58% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

portswigger.net https://portswigger.net/web-security/web-cache-poisoning referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by	version	score	vector
CNA	3.1	7.0	CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:H/A:L
NVD	3.1	6.1	CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
NVD	2.0	4.0	AV:N/AC:H/Au:N/C:P/I:P/A:N
GitHub	3.1	7.0	CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:H/A:L

Affected packages

ecosystem	package	affected	fixed in
maven	io.ratpack:ratpack-core	<1.9.0	1.9.0

Affected products

ratpack ratpack

Classification

Weakness

CWE-807 Reliance on Untrusted Inputs in a Security Decision

References

portswigger.net /web-security/web-cache-poisoning
web, exploit, third-party-advisory
github.com /ratpack/ratpack/security/advisories/GHSA-w6rq-6h34-vh7q
web, third-party-advisory
nvd.nist.gov /vuln/detail/CVE-2021-29479
advisory
github.com /ratpack/ratpack
package

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

Summary