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CVE-2026-42573 medium CVSS 6.1

Cross-Site Scripting (XSS) in svelte (CVE-2026-42573)

Summary

Cross-site scripting in svelte (CVE-2026-42573). Risk of unauthorized operations or information disclosure. Exploitable via name. Mitigation: upgrade to 5.55.7 or later.

Original description

The description as published by the source.

Svelte was vulnerable to DOM clobbering of its internal framework state on elements, potentially leading to XSS attacks.

You are vulnerable if all of the following is true:

  • you are using attribute spreading on a form element
  • you are using attribute spreading or allow a dynamic value for the name attribute on an input or button element within that form
  • both of these are simultaneously user-controllable

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-2026-42573 has been found in svelte.
Attackers can target a specific entry point like name over the network to misuse the product.
Risk of unauthorized operations or information disclosure. CVSS score: 6.1/10.
What to do: upgrade svelte to 5.55.7 or later.
If unsure, ask your IT team or search "svelte CVE-2026-42573" on the vendor's site.

CVE-2026-42573 (svelte) — CWE-79 / CVSS v3 6.1
Attack vector: remote (network-reachable) / unauthenticated
Attack surface: name
Patched: 5.55.7 — apply immediately
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

Cross-site scripting (XSS) (CWE-79) exists in svelte. Attackers reach the vulnerable code path via name without authentication.

📍 Affected scope

Check the vendor advisory for the affected versions of svelte. Attack surface: name.

🔥 Severity

Severity: Medium (CVSS 6.1/10). Risk of unauthorized operations or information disclosure.

🔧 How to fix

Update to 5.55.7.

🛡️ Workaround

Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.

🔍 Detection

Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Run grep -r 'svelte' . 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 'svelte' . | 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 svelte 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 patch patch 
    Upgrade svelte to 5.55.7

    ステージング環境で 5.55.7 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。

  3. 3
    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 svelte
[{"type":"SEMVER","events":[{"introduced":"0"},{"fixed":"5.55.7"}]}]

References

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