SB2026100824 - Multiple vulnerabilities in IBM PowerVC
Published: October 8, 2026
Breakdown by Severity
- Low
- Medium
- High
- Critical
Description
This security bulletin contains information about 2 vulnerabilities.
1) Algorithm Downgrade (CVE-ID: CVE-2026-55953)
CWE-ID: CWE-757 - Selection of Less-Secure Algorithm During Negotiat
CVSSv4: 9.3 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N]
The vulnerability allows a remote attacker to read and modify data transmitted over the connection.
The vulnerability exists due to selection of a less-secure algorithm during negotiation in the OTP TLS/DTLS client cipher suite validation logic when processing a ServerHello message. A remote attacker can select an anonymous cipher suite that was not offered by the client to read and modify data transmitted over the connection.
This affects TLS versions up to 1.2 and all DTLS versions, while TLS-1.3 connections are not affected. The issue can bypass the client's verify_peer setting because anonymous cipher suites do not require a server certificate.
2) Uncontrolled Recursion (CVE-ID: CVE-2026-58227)
CWE-ID: CWE-674 - Uncontrolled Recursion
CVSSv4: 8.7 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N]
The vulnerability allows a remote attacker to cause a denial of service.
The vulnerability exists due to uncontrolled recursion in certificate chain path building when processing peer certificate messages during a partial TLS or DTLS handshake. A remote attacker can send a certificate chain containing two mutually cross-signed certificates in unordered form to cause a denial of service.
No authentication or completed handshake is required, and both client and server sides are affected.
Remediation
Install update from vendor's website.