CVE-2026-15554: Undertow-core: undertow: authentication bypass via ajp ssl_cert/is_ssl forgery
Vulnerability summary
CVE-2026-15554 is a high (CVSS 7.4) Improper Certificate Validation vulnerability in undertow. EPSS estimates a 0.48% chance of exploitation in the next 30 days, higher than 41.5% of scored vulnerabilities.
Severe, CVSS 7.4 (CVE.org); no exploitation reported by the 5 checked sources; EPSS 0% (FIRST, 03-11-2026)
Source freshness unavailable
How is this decided?Advisory lineage
Upstream 0 · Downstream 6Timeline
- 11-08-2026PublishedVulnerability first disclosed.
- 01-11-2026Last modifiedVulnerability information updated.
Description
the Undertow AJP listener honours forged ssl_cert and is_ssl AJP attributes without requiring any shared-secret authentication. This enables an unauthenticated attacker with direct TCP access to port 8009 to bypass CLIENT-CERT authentication by injecting a forged X.509 certificate via the AJP protocol.
CVSS metrics
4 scores · 4 sources · 1 version- OSV · UbuntuEcosystem advisory · calculated7.4HighCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N
- OSV · DebianEcosystem advisory · calculated7.4HighCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N
- NVDNIST7.4HighCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N
EPSS trend
Probability
0.48%
Chance of exploitation in the next 30 days
Percentile
42%
Versus all other CVEs
30-day change
Increase +0.13 pp
From 0.35% on 04-10-2026
Known exploited
Compare KEV catalogs
CISA KEVNot in the CISA KEV catalog.
ENISA CNWNot in the ENISA CNW catalog.
CIRCLNot in the CIRCL catalog.
Public exploits
0 foundNo public exploits indexed.
Weaknesses
CWE · root causeAffected systems
Known conditions: network-reachable, no authentication, no user interaction (CVSS vector). Other conditions: not stated in public data.
Debian1 product
- undertowAll versions (No fix recorded)
Ubuntu1 product
- undertowAll versions (No fix recorded)
2 vendors · 2 products
