Bug 2521778 (CVE-2026-75899) - CVE-2026-75899 fast-uri: fast-uri: Server-Side Request Forgery via repeated hostname percent-decoding
Summary: CVE-2026-75899 fast-uri: fast-uri: Server-Side Request Forgery via repeated h...
Keywords:
Status: NEW
Alias: CVE-2026-75899
Product: Security Response
Classification: Other
Component: vulnerability
Version: unspecified
Hardware: All
OS: Linux
high
high
Target Milestone: ---
Assignee: Product Security DevOps Team
QA Contact:
URL:
Whiteboard:
Depends On: 2526721 2526722 2526727 2526728
Blocks:
TreeView+ depends on / blocked
 
Reported: 2026-08-24 09:51 UTC by OSIDB Bzimport
Modified: 2026-09-01 10:20 UTC (History)
99 users (show)

Fixed In Version:
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Description OSIDB Bzimport 2026-08-24 09:51:28 UTC
fast-uri is a URI parser for Node.js. It decodes percent escapes in a hostname during parsing and then decodes the parsed hostname a second time during authority recomposition, so a single call to normalize or resolve can turn nested percent-encoded input into a different network destination such as a loopback hostname or address. For example, a doubly encoded host that spells out a loopback name decodes to that live host in one operation, which contradicts RFC 3986 section 2.4 that an implementation must not decode the same string more than once. An application that normalizes or resolves an untrusted HTTP-family URI before outbound routing, redirect validation, or a host-policy check can receive a destination different from the one the original encoded host represented, giving a server-side request forgery and host-policy bypass primitive. This is an incomplete-fix variant of CVE-2026-6322. The affected versions are 2.4.1 up to but not including 2.4.5, 3.1.2 up to but not including 3.1.6, and 4.0.0 up to but not including 4.1.3. The issue is fixed in 2.4.5, 3.1.6, and 4.1.3, which normalize percent escapes once and preserve encoded percent signs. Users should upgrade to a patched version.


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