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CVE-2026-13676 high CVSS 7.5

Vulnerability in fast-uri (CVE-2026-13676)

Summary

Vulnerability in fast-uri (CVE-2026-13676). Data can be tampered with by attackers. Exploitable via URL. Mitigation: upgrade to 2.4.2 or later.

Original description

The description as published by the source.

Impact

fast-uri versions >= 2.3.1, <= 4.0.0 fail to canonicalize Unicode/IDN hostnames for HTTP-family URLs. The IDN conversion path calls URL.domainToASCII(...) on the global WHATWG URL constructor, where that helper does not exist. The resulting TypeError is silently routed into parsed.error, but parse(), normalize(), and equal() all return with the host left in its original Unicode form.

For example, http://127。0。0。1/ is treated by fast-uri as host 127。0。0。1, while Node's WHATWG URL parser and fetch() canonicalize the same input to 127.0.0.1.

Applications that use fast-uri to enforce host-based policy (denylists, loopback filtering, redirect validation, outbound proxy routing) before passing the same URL into Node's URL or fetch() consumers see a policy/use desync and can be steered to an unintended destination.

Patches

Upgrade to fast-uri v4.0.1, v3.1.3, or v2.4.2

Workarounds

None. Upgrade to the patched version.

Source: NIST National Vulnerability Database 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-2026-13676 has been found in fast-uri.
Attackers can target a specific entry point like URL over the network to misuse the product.
Data can be tampered with by attackers. CVSS score: 7.5/10.
What to do: upgrade fast-uri to 2.4.2 or later.
If unsure, ask your IT team or search "fast-uri CVE-2026-13676" on the vendor's site.

CVE-2026-13676 (fast-uri) — CWE-436 / CVSS v3 7.5
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Attack surface: URL / TypeError / parsed.error
Patched: 2.4.2 — 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

A vulnerability (CWE-436) exists in fast-uri. Attackers reach the vulnerable code path via URL without authentication.

📍 Affected scope

Check the vendor advisory for the affected versions of fast-uri. Attack surface: URL / TypeError / parsed.error.

🔥 Severity

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

🔧 How to fix

Update to 2.4.2.

🛡️ 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 2.4.2

    ステージング環境で 2.4.2 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":"2.4.2"}]}]

Fix status by distribution

Fixed packages published by each distribution for this CVE

References

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