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Response snapshot Oct 26, 2026, 22:02 UTC

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VulnerabilityCVE-2026-110095

fast-uri vulnerable to improper path equivalence in relative reference normalization

`fast-uri`'s `normalize()` and `serialize()` apply RFC 3986 dot-segment removal (`remove_dot_segments`) to the path of a relative-path reference. RFC 3986 section 5.2.

Published Updated

At a glance

Exploited
Not known
Severity
3.7 Low (CVSS 3.1)
Chance of exploitation
0.3% in the next 30 days
Sources
1 source

What to do

GitHub lists first patched versions: fast-uri: 2.4.8; fast-uri: 3.1.9; fast-uri: 4.2.3. Confirm the affected range and upgrade guidance in the exact advisory.

Read GitHub-reviewed advisory GHSA-xhq7-xmqj-769h (opens a new tab)

What happened

### Impact

`fast-uri`'s `normalize()` and `serialize()` apply RFC 3986 dot-segment removal (`remove_dot_segments`) to the path of a relative-path reference. RFC 3986 section 5.2.4 defines that algorithm only for the merged target path during resolution, not for the reference itself, so applied to the reference it drops leading `..` segments and can turn a document-relative reference into a root-relative one.

For example, `normalize('a/../b')` returns `/b` and `normalize('../x')` returns `x`, so `resolve(base, normalize(ref))` points at a different resource than `resolve(base, ref)`, and `equal()` treats distinct references as the same.

Applications that normalize attacker-supplied or user-supplied relative references and then resolve them, or use them as cache, deduplication, or authorization keys, can have a reference escape its intended directory and point at a different resource.

Continue reading

### Patches

Upgrade to `fast-uri` `2.4.8`, `3.1.9`, or `4.2.3`.

### Workarounds

Do not normalize a relative reference before resolving it. Resolve it against the absolute base first, then normalize the absolute result.

Affected package ranges reported by GitHub: fast-uri: < 2.4.8 fast-uri: >= 3.0.0, < 3.1.9 fast-uri: >= 4.0.0, < 4.2.3

Scores and how they were measured

CVSS base severity

3.7

Version 3.1As of

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N

Measurement source (opens a new tab)

How bad it is if exploited. Not a prediction of exploitation or proof you are exposed.

EPSS probability

0.3%

Scored Percentile 21.3%

Model and measurement source (opens a new tab)

A model's estimate of exploitation in the next 30 days, not certainty or your own risk.

Related technology

Sources

  1. Primary source

    GitHub-reviewed advisory GHSA-xhq7-xmqj-769h (opens a new tab)

    The public advisory supplies the description, affected package/version ranges, and any listed CVSS metric. GitHub review is not local review.

    Published Checked

  2. Primary source

    GitHub public advisory API page (opens a new tab)

    The API page supplied GHSA-xhq7-xmqj-769h, its actual identifiers, source dates, and structured metrics.

    Published Date not suppliedChecked

  3. Primary source

    FIRST measured EPSS score (opens a new tab)

    Measured EPSS probability and percentile for CVE-2026-110095, scored 2026-10-26. This is a model estimate, not proof of exposure.

    Published Checked

Cite this record

For factual claims, cite the primary sources above; cite KEVWire for its compilation, dates, and classifications.

APA

KEVWire. (2026, October 23). fast-uri vulnerable to improper path equivalence in relative reference normalization (CVE-2026-110095). https://kevwire.com/record/CVE-2026-110095

MLA

"fast-uri vulnerable to improper path equivalence in relative reference normalization (CVE-2026-110095)." KEVWire, 23 Oct. 2026, kevwire.com/record/CVE-2026-110095.

Chicago

KEVWire. "fast-uri vulnerable to improper path equivalence in relative reference normalization (CVE-2026-110095)." Last modified October 23, 2026. https://kevwire.com/record/CVE-2026-110095.

Evidence summary (plain text)

fast-uri vulnerable to improper path equivalence in relative reference normalization (Oct 23, 2026).
`fast-uri`'s `normalize()` and `serialize()` apply RFC 3986 dot-segment removal (`remove_dot_segments`) to the path of a relative-path reference. RFC 3986 section 5.2.4 defines that algorithm only for the merged target path during resolution, not for the reference itself, so applied to the reference it drops leading `..` segments and can turn a document-relative reference into a root-relative one.

For example, `normalize('a/../b')` returns `/b` and `normalize('../x')` returns `x`, so `resolve(base, normalize(ref))` points at a different resource than `resolve(base, ref)`, and `equal()` treats distinct references as the same.
CVSS 3.7 (version 3.1; evidence as of Oct 23, 2026; https://github.com/advisories/GHSA-xhq7-xmqj-769h).
EPSS 0.3% for the following 30 days, scored Oct 26, 2026 (https://api.first.org/data/v1/epss?cve=CVE-2026-110095&date=2026-10-26).
Sources:
GitHub-reviewed advisory GHSA-xhq7-xmqj-769h: https://github.com/advisories/GHSA-xhq7-xmqj-769h
GitHub public advisory API page: https://api.github.com/advisories?type=reviewed&per_page=100&sort=updated&direction=desc
FIRST measured EPSS score: https://api.first.org/data/v1/epss?cve=CVE-2026-110095&date=2026-10-26
Record ID: CVE-2026-110095.
Record origin: Ingested record.
AI evidence: Not assessed.
Known exploitation: Not assessed.
Zero-day status: Not assessed. KEV membership alone does not establish zero-day status.
About this data

This record was ingested from a data source. Retrieved: Oct 26, 2026, 19:40 UTC. Ingestion is not an independent editorial investigation.

A CISA KEV listing documents known exploitation, not necessarily a zero-day; absence from the catalog does not prove a vulnerability has never been exploited.

Technology tags indicate possible relevance, not verified exposure. Confirm the affected product, version, and configuration against your own inventory; KEVWire does not scan your systems.

A personal reading checklist on this device, not verified remediation.

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