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CVE Record

CVE-2026-6321: fast-uri vulnerable to path traversal via percent-encoded dot segments

fast-uri decoded percent-encoded path separators and dot segments before applying dot-segment removal in its normalize() and equal() functions. Encoded path data was treated like real slashes and parent-directory references, so distinct URIs could collapse onto the same normalized path. Applications that normalize or compare attacker-controlled URLs to enforce path-based policy can be bypassed, with a path that appears confined under an allowed prefix normalizing to a different location. Versions <= 3.1.0 are affected. Update to 3.1.1 or later.

HighCVSS 7.5Not KEV-listedUpdated
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Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

fast-uri could treat encoded path characters as real directory separators before cleanup. A URL that looks inside an allowed path could be normalized as something else, bypassing path-based checks in applications that rely on this library.

Executive priority

Prioritize remediation for internet-facing services or gateways that use URL path checks for access control. The issue is high severity because it can undermine integrity controls without authentication or user interaction.

Technical view

In fast-uri <=3.1.0, normalize() and equal() decode percent-encoded separators and dot segments before dot-segment removal. This can collapse distinct URIs into the same normalized path, affecting integrity where applications enforce policy by normalized URL path comparison.

Likely exposure

Exposure is most likely in JavaScript applications using fast-uri <=3.1.0 on attacker-controlled URLs for allowlists, routing decisions, proxy controls, file-path gates, or other path-prefix authorization checks.

Exploitation context

The supplied bundle does not show KEV listing or confirmed active exploitation. Exploitability is network-reachable with low complexity when a vulnerable application makes security decisions from fast-uri normalization or equality results.

Researcher notes

The key condition is not merely dependency presence; impact depends on security-sensitive use of normalize() or equal(). Validate whether encoded path data can influence policy decisions, while avoiding assumptions beyond the disclosed fast-uri behavior.

Mitigation direction

  • Update fast-uri to 3.1.1 or later.
  • Review vendor advisories for downstream Red Hat package status.
  • Avoid relying only on normalized string prefix checks for authorization.
  • Add defensive validation around attacker-controlled URL paths.

Validation and detection

  • Inventory package manifests and lockfiles for fast-uri versions <=3.1.0.
  • Find code using normalize() or equal() on untrusted URLs.
  • Review path-based authorization, allowlist, and proxy checks using fast-uri output.
  • Confirm deployed builds include fast-uri 3.1.1 or later.
  • Add regression tests for encoded separators and dot segments.
Prepared
Confidence
high
Sources
8

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

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cwe · medium confidence lookup

CWE-22: File access and web shell behavior lookup

File traversal and upload weaknesses can lead teams to review file, web shell, execution, and collection telemetry. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.

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description · low confidence lookup

File access behavior lookup

The CVE wording references file access or upload behavior, so file telemetry and web shell review may help. This is a Glexia inferred lookup path, not an official MITRE, ATT&CK, or CVE Program mapping.

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cve · low confidence lookup

CVE-2026-6321 mapping review

Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.

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Vulnerability profileCVE Program record
Severity
High
CVSS
7.5 (3.1)
Known Exploited
No
Published

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

Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

2CVSS vectors
5Timeline events
2ADP providers
21Source links

SSVC decision data

CISA-ADPCISA Coordinator
Timestamp
Version
2.0.3
Exploitation: noneAutomatable: yesTechnical Impact: partial

CVSS vector scores

2 official scores

We collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.

ScoreVersionSeverityVectorExploitImpactSource
7.5CVSS 3.1HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N3.93.6openjs
7.5CVSS 3.1HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N3.93.6redhat-SADP

Vulnerability scoring details

Base CVSS 3.1 score

7.5High
CVSS 3.1 vector shape for CVE-2026-6321Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

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

Attack Vector
NetworkAdjacentLocalPhysical
Attack Complexity
LowHigh
Privileges Required
NoneLowHigh
User Interaction
NoneRequired
Scope
ChangedUnchanged
Confidentiality Impact
HighLowNone
Integrity Impact
HighLowNone
Availability Impact
HighLowNone

Vulnerability timeline

Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.

  1. CVE reservedCVE Program

    The CVE ID was reserved by the assigning CNA.

  2. ADP timelineredhat-SADP

    Made public.

  3. CVE publishedCVE Program

    The CVE record was published.

  4. ADP timelineredhat-SADP

    Reported to Red Hat.

  5. CVE updatedCVE Program

    The CVE record metadata indicates this as the latest update time.

ADP provider summaries

CISA-ADPCISA ADP Vulnrichment
other:ssvc
redhat-SADPfast-uri: fast-uri: Path traversal vulnerability allows bypass of security policies
other:Red Hat severity ratingcvssV3_1
  • 2026-05-04T20:01:14.938Z: Reported to Red Hat.
  • 2026-05-04T19:31:57.253Z: Made public.

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
fast-urifast-uri0, 3.1.1unaffected
Weakness

CWE details

CWE-22

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.

CWE-22 · source CWE mapping

Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')

Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal') represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.

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