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CVE-2026-6321 high CVSS 7.5

Path Traversal in fast-uri (CVE-2026-6321)

Summary

Path traversal in fast-uri (CVE-2026-6321). Data can be tampered with by attackers. Mitigation: upgrade to 2.4.1 or later.

Original description

The description as published by the source.

Impact

fast-uri v3.1.0 and earlier decodes percent-encoded path separators (%2F) and dot segments (%2E) before applying dot-segment removal in normalize() and equal(). This makes encoded path data behave like real / and .., so distinct URIs collapse onto the same normalized path.

For example, http://example.com/public/%2e%2e/admin normalizes to http://example.com/admin, and equal() considers them the same URI.

Applications that normalize or compare attacker-controlled URLs to enforce path-based policy can be bypassed. A path that looks confined under an allowed prefix can normalize to a different location.

Patches

Upgrade to fast-uri >= 3.1.1, or if you are in the v2.x release line, v2.4.1

Workarounds

None. Upgrade to the patched version.

Source: GitHub Security Advisories (Global) NVD GitHub Advisory

Auto-generated summary

Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.

A vulnerability tracked as CVE-2026-6321 has been found in fast-uri.
Data can be tampered with by attackers. CVSS score: 7.5/10.
What to do: upgrade fast-uri to 2.4.1 or later.
If unsure, ask your IT team or search "fast-uri CVE-2026-6321" on the vendor's site.

CVE-2026-6321 (fast-uri) — CWE-22 / CVSS v3 7.5
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Patched: 2.4.1 — apply immediately
Workaround: None.
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.

❓ What is the problem

Path traversal (CWE-22) exists in fast-uri.

📍 Affected scope

Check the vendor advisory for the affected versions of fast-uri.

🔥 Severity

Severity: High (CVSS 7.5/10). Data can be tampered with by attackers.

🔧 How to fix

Update to 2.4.1.

🛡️ Workaround

Workaround: None.

🔍 Detection

Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Run grep -r 'fast-uri' . against your dependency files (package-lock.json, requirements.txt, go.sum) to find affected services.

Response actions

Concrete steps and command examples for SOC/SRE teams to execute in order

  1. 1
    Identify exposure identify 
    grep -r 'fast-uri' . | grep -v node_modules

    リポジトリと本番環境の依存ファイル (package-lock.json / requirements.txt / go.sum / Gemfile.lock 等) で fast-uri を grep し、稼働しているサービス・バージョンを把握する。

  2. 2
    Apply temporary workaround mitigate 
    None.

    パッチが適用されるまでの応急処置として、None. を実施。回避策の副作用 (機能低下) を確認した上で。

  3. 3
    Apply patch patch 
    Upgrade fast-uri to 2.4.1

    ステージング環境で 2.4.1 に上げて回帰テスト → 本番反映。回帰テストはアプリの主要ハッピーパスを含めること。

  4. 4
    Post-deployment verification verify 
    Confirm patched version is live in production

    パッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。

Affected packages

npm fast-uri
[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"2.4.1"}]}]

Fix status by distribution

Fixed packages published by each distribution for this CVE

References

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