Description

IBM i 7.6, 7.5, 7.4, and 7.3 could allow a remote attacker to cause a denial of service due to the use of uninitialized memory during ASN.1 length processing.

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "8.1",
  "pubDate": "2026-08-13T20:17:15.883Z",
  "pubdate": "2026-08-13T20:17:15.883Z",
  "executiveSummary": "This vulnerability represents a denial of service security flaw residing within IBM i versions 7.3, 7.4, 7.5, and 7.6. The fundamental weakness stems from improper handling during ASN.1 length processing, which results in the utilization of uninitialized memory. An unauthenticated remote attacker can exploit this defect to compromise system availability.\nThe potential impact of successful exploitation is a complete denial of service, rendering the affected IBM i environment unresponsive or causing critical service termination. The attack vector is network-based, allowing remote threat actors to trigger the flaw without requiring prior authentication or elevated privileges.\nGiven the core nature of ASN.1 parsing in network protocols and security layers, exploitation requires crafting specific payloads designed to interact with the vulnerable parsing routines. The primary risk implication is operational disruption, potentially impacting enterprise workloads relying on the affected IBM i systems. Organizations operating the specified versions must prioritize applying official vendor updates or implementing strict network segmentation and protocol filtering to mitigate exposure until remediation is complete.",
  "technicalDetails": "The vulnerability resides in the ASN.1 (Abstract Syntax Notation One) parsing subsystem of IBM i 7.3, 7.4, 7.5, and 7.6. ASN.1 is extensively used for defining data structures in networking and cryptographic protocols, requiring precise decoding of type, length, and value (TLV) encodings. The root cause of the flaw is the processing of ASN.1 length fields without proper initialization or validation of memory buffers prior to use.\nDuring typical operation, the vulnerable component parses incoming ASN.1 encoded byte streams. When processing maliciously crafted or malformed length indicators, the parsing routine references uninitialized memory locations. This anomalous memory state leads to undefined behavior, memory corruption, or exception faults that crash the parsing service or exhaust system resources.\nThe attack flow begins when a remote attacker transmits a network packet containing a maliciously manipulated ASN.1 structure to a vulnerable service running on IBM i. The service ingests the payload and passes it to the ASN.1 decoding engine. Because the length processing logic fails to properly initialize or validate the memory associated with the length descriptor, the application attempts to read or operate on stale, residual, or uninitialized memory contents.\nThis programmatic failure triggers an unhandled exception, segmentation fault, or infinite loop depending on the exact memory state, resulting in a denial of service condition. The vulnerability requires no user interaction, authentication, or privileged access, meaning any remote actor capable of reaching the vulnerable network service can initiate the attack payload.\nPost-exploitation impact is strictly confined to availability degradation or service disruption; there is no direct indication of remote code execution or arbitrary data disclosure based on the uninitialized memory usage during length processing. Remediation requires deploying the appropriate vendor-supplied Program Temporary Fixes (PTFs) designed to correct the ASN.1 parsing logic and ensure proper memory initialization."
}