Security Bulletin
Summary
IBM Terracotta uses undertow as an embedded web server.
Vulnerability Details
CVEID: CVE-2026-15554
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.
CWE: CWE-295: Improper Certificate Validation
CVSS Source: secalert@redhat.com
CVSS Base score: 7.4
CVSS Vector: (CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N)
CVEID: CVE-2026-15561
DESCRIPTION: A flaw was found in EAP's undertow http/1.1 chunked-transfer decoder. missing limits on size and count would allow an attacker to use an unauthenticated connection to drive the JVM to an OutOfMemory error, stopping all deployments on the listener, and achieving Denial of Service.
CWE: CWE-770: Allocation of Resources Without Limits or Throttling
CVSS Source: secalert@redhat.com
CVSS Base score: 7.5
CVSS Vector: (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H)
CVEID: CVE-2026-19879
DESCRIPTION: A flaw was found in Undertow, an HTTP server, within its HTTP response header writing path. The `writeString()` method performs a silent narrowing cast from 16-bit Unicode characters to 8-bit bytes when writing HTTP response header values. A remote attacker can exploit this by supplying specific Unicode characters in user-controlled input that an application places into response headers. This can lead to the truncation of these characters into ASCII control characters or special symbols, potentially resulting in limited integrity impact or information disclosure if the application does not properly sanitize user input.
CWE: CWE-681: Incorrect Conversion between Numeric Types
CVSS Source: secalert@redhat.com
CVSS Base score: 5.3
CVSS Vector: (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N)
Affected Products and Versions
| Affected Product(s) | Version(s) |
| IBM Terracotta |
12.1 - 12.1.0.3 11.1 - 11.1.0.20 10.15 - 10.15.0.38 |
Remediation/Fixes
IBM strongly suggests that you address the vulnerabilities now by installing the latest version of each product:
| Product(s) | Version(s) |
| IBM Terracotta |
12.1.0.4 11.1.0.21 10.15.0.39 |
Installation is available via:
- IBM webMethods Update Manager (How to Download webMethods Software)
- Fix Central (IBM Support: Fix Central)
Workarounds and Mitigations
None
Get Notified about Future Security Bulletins
References
Acknowledgement
Change History
10 Sep 2026: Initial Publication
*The CVSS Environment Score is customer environment specific and will ultimately impact the Overall CVSS Score. Customers can evaluate the impact of this vulnerability in their environments by accessing the links in the Reference section of this Security Bulletin.
Disclaimer
According to the Forum of Incident Response and Security Teams (FIRST), the Common Vulnerability Scoring System (CVSS) is an "industry open standard designed to convey vulnerability severity and help to determine urgency and priority of response." IBM PROVIDES THE CVSS SCORES ""AS IS"" WITHOUT WARRANTY OF ANY KIND, INCLUDING THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. CUSTOMERS ARE RESPONSIBLE FOR ASSESSING THE IMPACT OF ANY ACTUAL OR POTENTIAL SECURITY VULNERABILITY. In addition to other efforts to address potential vulnerabilities, IBM periodically updates the record of components contained in our product offerings. As part of that effort, if IBM identifies previously unidentified packages in a product/service inventory, we address relevant vulnerabilities regardless of CVE date. Inclusion of an older CVEID does not demonstrate that the referenced product has been used by IBM since that date, nor that IBM was aware of a vulnerability as of that date. We are making clients aware of relevant vulnerabilities as we become aware of them. "Affected Products and Versions" referenced in IBM Security Bulletins are intended to be only products and versions that are supported by IBM and have not passed their end-of-support or warranty date. Thus, failure to reference unsupported or extended-support products and versions in this Security Bulletin does not constitute a determination by IBM that they are unaffected by the vulnerability. Reference to one or more unsupported versions in this Security Bulletin shall not create an obligation for IBM to provide fixes for any unsupported or extended-support products or versions.
Document Location
Worldwide
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Document Information
Modified date:
10 September 2026
Initial Publish date:
10 September 2026
UID
ibm17286994