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Public proof of conceptFix available

CVE-2025-12543

A public proof of concept exists; no exploitation attested.

  • Published2026-01-07
  • Fixed in8.1.3 · 8.0.12
  • WeaknessCWE-20

Am I affected?

With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.

Description

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.

Timeline

dates in UTC
  1. 2026-01-0717:15CVE publishedNVD
  2. 2026-10-2319:23First public proof of conceptPoC-in-GitHub

Observed activity

isMalicious corpus · updated 2026-10-23 18:48 UTC
Indicators tagged with this CVE, per day0 indicators over 7 days
Block these indicators
  • Firewall list (EDL, text): https://api.ismalicious.com/edl/cve/CVE-2025-12543?format=txt
  • CSV export: https://api.ismalicious.com/edl/cve/CVE-2025-12543?format=csv
  • TAXII collection of exploited CVEs
  • The EDL and CSV take an API key on the Pro plan.

Versions per branch

NVD
Redhat jboss enterprise application platform
BranchAffectedFixed in
8.1≥ 8.1.0, < 8.1.38.1.3
8.0≥ 8.0, < 8.0.128.0.12
—all versionsno fix published
7.0= 7.0.0no fix published
Redhat undertow
BranchAffectedFixed in
2.3≥ 2.3.0, < 2.3.212.3.21
2.2< 2.2.392.2.39
Redhat build of apache camel
BranchAffectedFixed in
4.14< 4.14.44.14.4

5 more products in the sources.

as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.

Distribution builds and vendor advisories

Packages from OSV.dev and products from the vendors' CSAF advisories.

version not verifiedVersions not verified: read as OSV.dev and the vendors publish them, not checked against each vendor's release list.

Vendor advisories

  • RHSA-2026:76128 Red Hat Product Security3 products fixed

    Red Hat Security Advisory: Red Hat Single Sign-On 7.6.13 security update on RHEL 7

  • RHSA-2026:76130 Red Hat Product Security3 products fixed

    Red Hat Security Advisory: Red Hat Single Sign-On 7.6.13 security update on RHEL 9

  • RHSA-2026:76129 Red Hat Product Security3 products fixed

    Red Hat Security Advisory: Red Hat Single Sign-On 7.6.13 security update on RHEL 8

  • RHSA-2026:76134 Red Hat Product Security3 products fixed

    Red Hat Security Advisory: Red Hat Single Sign-On 7.6.13 for OpenShift image security update

  • RHSA-2026:76132 Red Hat Product Security1 product fixed

    Red Hat Security Advisory: Red Hat Single Sign-On 7.6.13 security update

Full record on NVD

Fix

  1. Update Redhat jboss enterprise application platform to 8.1.3 · 8.0.12
  2. Vendor fix Red Hat Product Security RHSA-2026:76128 · 3 productsBefore applying this update, make sure all previously released errata relevant to your system have been applied. For details on how to apply this update, refer to: https://access.redhat.com/articles/11258
  3. Vendor fix Red Hat Product Security RHSA-2026:76134 · 3 productsBefore applying this update, make sure all previously released errata relevant to your system have been applied. For details on how to apply this update, refer to: https://access.redhat.com/articles/11258
  4. Vendor fix Red Hat Product Security RHSA-2026:76132 · 1 productBefore applying the update, back up your existing installation, including all applications, configuration files, databases and database settings, and so on. The References section of this erratum contains a download link (you must log in to download the update).
  5. Workaround from the vendor Red Hat Product Security RHSA-2026:76128 · 3 productsMitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use, applicability, or stability.

Advisories and patches

Detection

read 2026-10-23 19:24 UTC
Nuclei template
none so far
ProjectDiscovery
Exploit-DB
no entry
Exploit-DB
Proof-of-concept repositories
1 repository, unverifiedkavin71725/CVE-2025-12543-Fix-for-Wildfly
PoC-in-GitHub

Sources

  • CISA-ADPSSVC decisionnone2026-01-08
  • OpenCVESSVC decisionnone—
  • CNACVSS 3.19.6read 2026-10-23
  • NVDCVSS 3.19.6read 2026-10-23
  • CNAweakness (CWE)CWE-20read 2026-10-23
  • FIRST EPSSEPSS score1.3 %2026-10-22
  • PoC-in-GitHubproof of concept1read 2026-10-23

Technical details

CVSS v3 Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H
Published
2026-01-07
Last Modified
2026-10-14
NVD status
Modified

Frequently asked questions

What is CVE-2025-12543?

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.

Is CVE-2025-12543 actively exploited?

Active exploitation of CVE-2025-12543 has not been confirmed. Its EPSS score was 1.3% on 2026-10-22, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2025-12543?

CVE-2025-12543 has a CVSS v3 base score of 9.6 (CRITICAL severity), with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:H/I:H/A:H.

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