Answer in brief
CVE-2025-12543 records a Critical severity (CVSS 9.6) vulnerability in Undertow-core: undertow http server fails to reject malformed host headers leading to potential cache poisoning and ssrf. The current sources do not mark it as known exploited. Affected software not mapped in the current feed; confirm the named product and version against your inventory.
Analysis pending evidence review
HOL Guard separates source facts from reviewed analysis. See the methodology.
Answer in brief
CVE-2025-12543 records a Critical severity (CVSS 9.6) vulnerability in Undertow-core: undertow http server fails to reject malformed host headers leading to potential cache poisoning and ssrf. The current sources do not mark it as known exploited. Affected software not mapped in the current feed; confirm the named product and version against your inventory.
Analysis pending evidence review
HOL Guard separates source facts from reviewed analysis. See the methodology.
CVSS is 9.6. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.
Analysis status
Analysis pending evidence review
Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.
Affected software not mapped in the current feed; confirm the named product and version against your inventory.
Published upstream
Jan 7, 2026
Evidence: source:cvelist:source_dates:source-dates:recordSource modified
Jul 28, 2026
Evidence: source:cvelist:source_dates:source-dates:recordFirst seen by HOL
Jun 25, 2026
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.
Quoted source text, attributed separately from HOL analysis.
CVSS is 9.6. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.
Analysis status
Analysis pending evidence review
Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.
Affected software not mapped in the current feed; confirm the named product and version against your inventory.
Published upstream
Jan 7, 2026
Evidence: source:cvelist:source_dates:source-dates:recordSource modified
Jul 28, 2026
Evidence: source:cvelist:source_dates:source-dates:recordFirst seen by HOL
Jun 25, 2026
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.
Quoted source text, attributed separately from HOL analysis.