Security Bulletin
Summary
OpenSSH used by IBM i is vulnerable to a machine-in-the-middle attack due to mishandling error codes when verifying the host key as described in the vulnerability details section. This bulletin identifies the steps to take to address the vulnerability as described in the remediation/fixes section.
Vulnerability Details
CVEID: CVE-2025-26465
DESCRIPTION: A vulnerability was found in OpenSSH when the VerifyHostKeyDNS option is enabled. A machine-in-the-middle attack can be performed by a malicious machine impersonating a legit server. This issue occurs due to how OpenSSH mishandles error codes in specific conditions when verifying the host key. For an attack to be considered successful, the attacker needs to manage to exhaust the client's memory resource first, turning the attack complexity high.
CWE: CWE-390: Detection of Error Condition Without Action
CVSS Source: NVD
CVSS Base score: 6.8
CVSS Vector: (CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:N)
Affected Products and Versions
| Affected Product(s) | Version(s) |
| IBM i | 7.6 |
| IBM i | 7.5 |
| IBM i | 7.4 |
| IBM i | 7.3 |
| IBM i | 7.2 |
Remediation/Fixes
The issue can be addressed by applying a PTF to IBM i. IBM i 7.6, 7.5, 7.4, 7.3, and 7.2 are addressed.
The IBM i 5733-SC1 PTF number resolves the vulnerability.
| IBM i Release | 5733-SC1 PTF Number | PTF Download Link |
| 7.6 | SJ05440 | https://www.ibm.com/mysupport/s/fix-information?legacy=SJ05440 |
| 7.5 | SJ05424 | https://www.ibm.com/mysupport/s/fix-information?legacy=SJ05424 |
| 7.4, 7.3, 7.2 | SJ05423 | https://www.ibm.com/mysupport/s/fix-information?legacy=SJ05423 |
https://www.ibm.com/support/fixcentral
Important note: IBM recommends that all users running unsupported versions of affected products upgrade to supported and fixed version of affected products.
Workarounds and Mitigations
None
Get Notified about Future Security Bulletins
References
Acknowledgement
Change History
14 May 2025: 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
Was this topic helpful?
Document Information
Modified date:
14 May 2025
UID
ibm17233399