Cross-Site Scripting (XSS) in Nextcloud Mail (CVE-2025-66514)
Summary
Cross-site scripting in Nextcloud Mail (CVE-2025-66514). Risk of unauthorized operations or information disclosure.
Original description
The description as published by the source.
Nextcloud Mail is the mail app for Nextcloud, a self-hosted productivity platform. Prior to 5.5.3, a stored HTML injection in the Mail app's message list allowed an authenticated user to inject HTML into the email subjects. Javascript was correctly blocked by the content security policy of the Nextcloud Server code.
Source: NIST National Vulnerability Database NVD
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-2025-66514 has been found in Nextcloud Mail.
Risk of unauthorized operations or information disclosure. CVSS score: 3.5/10.
What to do: apply the vendor's official patched release.
If unsure, ask your IT team or search "Nextcloud Mail CVE-2025-66514" on the vendor's site.
CVE-2025-66514 (Nextcloud Mail) — CWE-79 / CVSS v3 3.5
Attack vector: remote (network-reachable)
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.
Cross-site scripting (XSS) (CWE-79) exists in Nextcloud Mail.
Check the vendor advisory for the affected versions of Nextcloud Mail.
Severity: Low (CVSS 3.5/10). Risk of unauthorized operations or information disclosure.
Update to the patched release per vendor advisory.
Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.
Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Audit SBOM/dependencies to find affected services.
Response actions
Concrete steps and command examples for SOC/SRE teams to execute in order
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1Identify exposure identify
Audit SBOM/dependencies for affected components.資産台帳・SBOM・依存マニフェストで Nextcloud Mail を使っているサービスとバージョンを洗い出す。
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2Post-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。