9.6

CVE-2025-12543: Undertow-core: undertow http server fails to reject malformed host headers leading to potential cache poisoning and ssrf

Modified
AliasesUBUNTU-CVE-2025-12543DEBIAN-CVE-2025-12543CGA-2vj6-vxvp-57rq
Published 07-01-2026Last modified 14-10-2026

Vulnerability summary

CVE-2025-12543 is a critical (CVSS 9.6) Improper Input Validation vulnerability in redhat build_of_apache_camel. EPSS estimates a 1.33% chance of exploitation in the next 30 days, higher than 71.1% of scored vulnerabilities.

Priority
Prioritisesevere

Severe, CVSS 9.6 (CVE.org); no exploitation reported by the 5 checked sources; EPSS 1% (FIRST, 03-11-2026)

Source freshness unavailable

How is this decided?
CVSS score
9.6/10
010
Critical · v3.1 (CVE.org)
EPSS score
1.33%
0%100%
Low · 0.00 pp in 30 days
KEVNot listedNot listed by any tracked catalog.
RansomwareNot flaggedNo ransomware use recorded.
Public exploits0No public exploits recorded

Advisory lineage

Upstream 0 · Downstream 12 · Related 2
RHSA-2026:0383RHSA-2026:0384RHSA-2026:33371RHSA-2026:33372RHSA-2026:3889RHSA-2026:3891

Timeline

  1. 07-01-2026
    PublishedVulnerability first disclosed.
  2. 14-10-2026
    Last modifiedVulnerability information updated.

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.

CVSS metrics

7 scores · 7 sources · 1 version

EPSS trend

Probability

1.33%

Chance of exploitation in the next 30 days

Percentile

71%

Versus all other CVEs

30-day change

No change 0.00 pp

From 1.33% on 04-10-2026

04-10-202603-11-2026

Known exploited

Compare KEV catalogs
CISA KEV

Not in the CISA KEV catalog.

ENISA CNW

Not in the ENISA CNW catalog.

CIRCL

Not in the CIRCL catalog.

Public exploits

0 found

No public exploits indexed.

Weaknesses

CWE · root cause

Affected systems

Version check

Known conditions: network-reachable, no authentication, user interaction (CVSS vector). Other conditions: not stated in public data.

Redhat8 products
Chainguard2 products
  • wildfly-openjdk-17< 39.0.0-r0
  • wildfly-openjdk-21< 39.0.0-r0
Wolfi2 products
  • wildfly-openjdk-17< 39.0.0-r0
  • wildfly-openjdk-21< 39.0.0-r0
Debian1 product
  • undertowAll versions (No fix recorded)
Io.undertow1 product
  • undertow-core2.4.0.Alpha1 | ≥ 2.3.0.Alpha1, < 2.3.21.Final | < 2.2.39.Final
Ubuntu1 product
  • undertow< 1.3.16-1ubuntu0.1~esm1 | < 1.4.23-3ubuntu0.1~esm1 | < 2.0.29-1ubuntu0.1~esm1 | < 2.2.16-1ubuntu0.1~esm1 | < 2.3.8-2ubuntu0.1~esm1 | All versions (No fix recorded) | < 2.3.20-1ubuntu1

6 vendors · 15 products

References

37 links
Show all 37 references