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CVE-2025-12543 critical CVSS 9.6

Vulnerability in Undertow HTTP server core (CVE-2025-12543)

Summary

Vulnerability in Undertow HTTP server core (CVE-2025-12543). Confidential information can be exposed externally. Exploitable via Host header.

Original description

The description as published by the source.

A flaw was found in the Undertow HTTP server core, which is used in WildFly, JBoss EAP, and other Java applications. The Undertow library fails to properly validate the Host header in incoming HTTP requests.As a result, requests containing malformed or malicious Host headers are processed without rejection, enabling attackers to poison caches, perform internal network scans, or hijack user sessions.

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-2025-12543 has been found in Undertow HTTP server core.
Attackers can target a specific entry point like Host header over the network to misuse the product.
Confidential information can be exposed externally. CVSS score: 9.6/10.
What to do: apply the vendor's official patched release.
If unsure, ask your IT team or search "Undertow HTTP server core CVE-2025-12543" on the vendor's site.

CVE-2025-12543 (Undertow HTTP server core) — CWE-20 / CVSS v3 9.6
Attack vector: remote (network-reachable) / unauthenticated
Attack surface: Host header
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-20) exists in Undertow HTTP server core. Attackers reach the vulnerable code path via Host header without authentication.

📍 Affected scope

Check the vendor advisory for the affected versions of Undertow HTTP server core. Attack surface: Host header.

🔥 Severity

Severity: Critical (CVSS 9.6/10). Confidential information can be exposed externally.

🔧 How to fix

Update to the patched release per vendor advisory.

🛡️ 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. Audit SBOM/dependencies to find affected services.

Response actions

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

  1. 1
    Identify exposure identify 
    Audit SBOM/dependencies for affected components.

    資産台帳・SBOM・依存マニフェストで Undertow HTTP server core を使っているサービスとバージョンを洗い出す。

  2. 2
    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。

Fix status by distribution

Fixed packages published by each distribution for this CVE

References

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