fast-uri vulnerable to host confusion via percent-encoded scheme normalization
fast-uri is a URI parser for Node.js. During parsing it runs a legacy decoding pass over the scheme component and never re-escapes the result, and serialization writes the scheme back out verbatim, unlike the host component which is re-escaped. As a result an input whose scheme carries percent-encoded slashes parses as a scheme with no authority, so the parsed host and error are both undefined, yet resolving or normalizing that same input emits a network-path reference whose authority is attacker-chosen and re-parses to that host. An application that allowlists on the parsed host, or treats a reference with no authority as safe to resolve against its base, gets the opposite of what it checked, giving an off-site redirect, server-side request forgery, or address-policy bypass. The legacy decoder also expands non-standard escape forms, widening the issue past upstream filters, and control characters in the scheme can reach the output as raw carriage return and line feed. The affected versions are 2.3.1 up to but not including 2.4.5, 3.0.0 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 reject a scheme that is not valid after decoding. Users should upgrade to a patched version.
- Published
- Aug 24, 2026
- Updated
- Sep 2, 2026
- EPSS
- 0.2% · 13th percentile
- CWE
- CWE-177
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Report tools
Action score
30
Monitor
Low priority for now.
- CVSS
- 30 / 40 · 7.5 / 10
- CISA KEV
- 0 / 30 · Not listed
- EPSS
- 0 / 30 · 0.2%
CISA SSVC decision
- Exploitation
- none
- Automatable
- yes
- Technical impact
- partial
Vulnrichment: CISA's decision-tree inputs.
CNA vs NVD score
- NVD
- —
- CNA · openjs
- 7.5
- NVD has not scored this yet; the score shown is the CNA’s.
The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.
Noroxi analysis
No Noroxi analysis for this record yet
We don't hand-write analysis for the hundreds of thousands of vulnerabilities in the database; that wouldn't be honest. For notable, high-impact vulnerabilities our team writes the mechanism, detection and remediation steps.
We use this product, ask for helpAffected systems
| Vendor | Product | CPE |
|---|---|---|
| openjsf | fast-uri | cpe:2.3:a:openjsf:fast-uri |
Affected versions
NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.
- openjsf fast-uri2.3.1 and later · before 2.4.5
- openjsf fast-uri3.0.0 and later · before 3.1.6
- openjsf fast-uri4.0.0 and later · before 4.1.3
Versions reported by the vendor
Affected version ranges reported by the assigning authority (openjs). Independent of NVD's CPE analysis and usually ahead of it.
fast-uri fast-uri
- 2.4.5, 3.1.6, 4.1.3not affected
- 2.3.1 and later · before 2.4.5affected · semver
- 3.0.0 and later · before 3.1.6affected · semver
- 4.0.0 and later · before 4.1.3affected · semver
Package-level exposure
OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.
| Ecosystem | Package | Affected range | Fix |
|---|---|---|---|
| AlmaLinux:10 | cockpit-image-builder | before 94.4-1.el10_2 | 94.4-1.el10_2 |
| Debian:13 | node-ajv | all versions | — |
| Debian:14 | node-ajv | before 8.20.0~ds+~cs7.1.4-1 | 8.20.0~ds+~cs7.1.4-1 |
| npm | fast-uri | from 2.3.1 · before 2.4.5 | 2.4.5 |
| npm | fast-uri | from 3.0.0 · before 3.1.6 | 3.1.6 |
| npm | fast-uri | from 4.0.0 · before 4.1.3 | 4.1.3 |
| Red Hat:enterprise_linux:10.2 | cockpit-image-builder | before 0:94.4-1.el10_2 | 0:94.4-1.el10_2 |
| Red Hat:hummingbird:1 | grafana12.4 | before 0:12.4.9-0.4.hum1 | 0:12.4.9-0.4.hum1 |
| Red Hat:hummingbird:1 | grafana13.1 | before 0:13.1.3-0.3.hum1 | 0:13.1.3-0.3.hum1 |
| Red Hat:hummingbird:1 | grafana13.2 | before 0:13.2.0-0.1.2.hum1 | 0:13.2.0-0.1.2.hum1 |
| Rocky Linux:10 | cockpit-image-builder | before 0:94.4-1.el10_2 | 0:94.4-1.el10_2 |
Same product
openjsf: all recordsOther highest-scoring records for the same primary product.
- CVE-2026-84394fast-uri vulnerable to host confusion via an unclosed bracket in the URI authority30Monitor
- CVE-2026-84292fast-uri vulnerable to authority injection via an unvalidated port in serialize30Monitor
- CVE-2026-75975fast-uri vulnerable to server-side request forgery via malformed IPv6 normalization30Monitor
- CVE-2026-75931fast-uri vulnerable to host confusion via skipped IDN canonicalization on scheme-relative references30Monitor
- CVE-2026-75899fast-uri vulnerable to server-side request forgery via repeated hostname percent-decoding30Monitor
- CVE-2026-18446fast-uri vulnerable to host confusion via backslash authority introducer30Monitor
Remediation
Which version to upgrade to
Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.
| Product / package | Fixed version | Source |
|---|---|---|
| fast-uri fast-uri | 2.4.5 | Vendor (CNA) |
| fast-uri fast-uri | 3.1.6 | Vendor (CNA) |
| fast-uri fast-uri | 4.1.3 | Vendor (CNA) |
| almalinux:cockpit-image-builder | 94.4-1.el10_2 · AlmaLinux:10 | Package registry (OSV) |
| debian:node-ajv | 8.20.0~ds+~cs7.1.4-1 · Debian:14 | Package registry (OSV) |
| npm:fast-uri | 2.4.5 | Package registry (OSV) |
| npm:fast-uri | 3.1.6 | Package registry (OSV) |
| npm:fast-uri | 4.1.3 | Package registry (OSV) |
| red hat:cockpit-image-builder | 0:94.4-1.el10_2 · Red Hat:enterprise_linux:10.2 | Package registry (OSV) |
| red hat:grafana12.4 | 0:12.4.9-0.4.hum1 · Red Hat:hummingbird:1 | Package registry (OSV) |
| red hat:grafana13.1 | 0:13.1.3-0.3.hum1 · Red Hat:hummingbird:1 | Package registry (OSV) |
| red hat:grafana13.2 | 0:13.2.0-0.1.2.hum1 · Red Hat:hummingbird:1 | Package registry (OSV) |
| rocky linux:cockpit-image-builder | 0:94.4-1.el10_2 · Rocky Linux:10 | Package registry (OSV) |
Exploit status
No known public exploit
No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.
Research context
For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.
Timeline
From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.
No dated events beyond publication.
FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).
Patch and commit links
Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.
No commit or PR link among the references.
Credits
All researchersFinders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.
- YashvantHangereporter
- mcollinaremediation developer
- UlisesGasconremediation reviewer
Variant candidates
Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.
No nightly-computed relations.
Chain candidates
An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.
—
Bug bounty scope
No known public program.
Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).
Technical details
Attack conditions
- Anyone who can reach it over the internet can trigger it.
- No account or password is required.
- No user action is required.
- No special conditions are required; it is repeatable.
If successful
- Confidentiality
- none
- Integrity
- high · data or configuration can be modified
- Availability
- none
- Attack vector
- Network
- Attack complexity
- Low
- Privileges required
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality impact
- None
- Integrity impact
- High
- Availability impact
- None
Weakness class (CWE)
CWE-177 · Improper Handling of URL Encoding (Hex Encoding)CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
nvd-secondary
Attack context
MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.
Change log
- Fix✗ → ✓
For records you follow, these changes also arrive as notifications. →
References
- cna.openjsf.org/security-advisories.html
- github.com/fastify/fast-uri/security/advisories/GHSA-jqff-g426-hqxp
Vendor advisories and official records. Exploit/PoC links are deliberately left out.