Description

IBM AIX 7.2, and 7.3 and IBM PowerVM VIOS 4.1 could allow a remote attacker to cause a denial of service due to improper handling of a missing SSL client certificate.

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "7.5",
  "pubDate": "2026-08-19T20:17:04.710Z",
  "pubdate": "2026-08-19T20:17:04.710Z",
  "executiveSummary": "This security assessment analyzes a denial of service vulnerability affecting IBM AIX and IBM PowerVM VIOS products. The flaw stems from improper handling of a missing Secure Sockets Layer (SSL) client certificate during cryptographic handshake or session establishment phases.\nA remote, unauthenticated attacker can exploit this weakness to induce resource exhaustion or application instability, culminating in a denial of service condition on targeted systems. The vulnerability impacts availability by causing services to crash, hang, or become unresponsive when processing anomalous SSL client authentication requests.\nAffected software includes IBM AIX 7.2, IBM AIX 7.3, and IBM PowerVM VIOS 4.1. Exploitation requires network access to vulnerable services handling SSL/TLS connections. No elevated privileges or prior user authentication are strictly necessary to trigger the flaw, making it accessible to remote threat actors positioned along the network path.\nThe risk implication is critical for enterprise environments relying on these operating systems and virtualization management servers, as service disruption can severely impact underlying virtualized workloads and administrative capabilities.",
  "technicalDetails": "The root cause of the vulnerability lies within the cryptographic stack and connection handling routines of the affected IBM AIX and IBM PowerVM VIOS components. Specifically, the software fails to properly validate, parse, or gracefully handle scenarios where an expected SSL client certificate is omitted during mutual TLS (mTLS) authentication or optional certificate verification procedures.\nVulnerable components involve system daemons, management interfaces, or network services configured to process incoming secure connections that logic dictates should include cryptographic client credentials. When a client initiates a connection and omits the required SSL certificate, the exception handling routine within the SSL state machine experiences a logic error, null pointer dereference, unhandled exception, or unbounded resource consumption.\nThe attack flow begins when a remote attacker establishes a TCP connection to a vulnerable service listening on the network. The attacker proceeds through the initial TCP handshake and initiates the TLS negotiation phase. During the SSL/TLS handshake—specifically at the point where the server requests or anticipates an SSL client certificate—the attacker deliberately withholds the certificate or transmits a malformed structure.\nUpon receiving the handshake message lacking the expected client certificate, the vulnerable application attempts to parse the non-existent data structure. Due to improper input validation and deficient error handling, the application encounters an anomalous state. This triggers abnormal program termination, a segmentation fault, or locks internal execution threads, rendering the service entirely unresponsive to legitimate administrative or client traffic.\nThe affected versions explicitly comprise IBM AIX 7.2, IBM AIX 7.3, and IBM PowerVM VIOS 4.1. Authentication requirements are absent for the initial trigger, as the fault occurs during the pre-authentication cryptographic handshake phase. Privilege requirements are similarly non-existent for the remote attacker. Network exposure is determined by the accessibility of the vulnerable listening services, typically exposing management or core networking daemons to internal or external network zones.\nThe payload behavior is inherently destructive to availability, causing an immediate denial of service without yielding arbitrary code execution or unauthorized privilege escalation based on current operational parameters. Post-exploitation impact is strictly limited to service downtime, requiring administrative intervention such as service restarts or system reboots to restore normal functionality."
}