Host redirection via unvalidated port serialization
Published Sep 2, 2026 · Updated Sep 3, 2026
Authority injection in Fastify fast-uri before 2.4.6, 3.0.0 through 3.1.6, and 4.0.0 through 4.1.3 allows remote attackers to redirect URI hosts. recomposeAuthority escapes userinfo and host but appends a nondigit port verbatim, letting authority delimiters convert the intended host into userinfo. Exploitation requires a consuming application to place untrusted data in an object-form port passed to serialize, normalize, or equal, after which URI consumers accept the attacker-controlled host.
Summary
What happened
Authority injection in Fastify fast-uri before 2.4.6, 3.0.0 through 3.1.6, and 4.0.0 through 4.1.3 allows remote attackers to redirect URI hosts. recomposeAuthority escapes userinfo and host but appends a nondigit port verbatim, letting authority delimiters convert the intended host into userinfo. Exploitation requires a consuming application to place untrusted data in an object-form port passed to serialize, normalize, or equal, after which URI consumers accept the attacker-controlled host.
The record
- CVE
- CVE-2026-84292
- Published
- Sep 2, 2026
- Updated
- Sep 3, 2026
- Vendor
- Fastify
- Product
- fast-uri
- Classifications
- CWE-116
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Sep 2, 2026CVE publishedPublication date reported by the CVE source.
- Sep 3, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=0 <2.4.6
- Affected versionversion=3.0.0 <3.1.7
- Affected versionversion=4.0.0 <4.1.4
What conditions does exploitation require?
What is affected?
Published CVSS scores
CVSS describes severity. EPSS estimates exploitation probability.
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Weakness, pattern, technique
Public exploit references
- Upstream malicious-port demonstrationproof of concept · demonstrated
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Technologies
Your stack
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Your stack
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