IBM i Off-by-One Bounds Checking DoS in 7.6/7.5/7.4/7.3
CVE-2026-18020 Published on August 13, 2026
IBM i is Affected By Multiple Vulnerabilities in NetServer
IBM i 7.6, 7.5, 7.4, and 7.3 could allow a remote attacker to cause a denial of service due to an off-by-one error in bounds checking.
Vulnerability Analysis
CVE-2026-18020 is exploitable with network access, and does not require authorization privileges or user interaction. This vulnerability is considered to have a low attack complexity. The potential impact of an exploit of this vulnerability is considered to have no impact on confidentiality and integrity, and a small impact on availability.
Weakness Type
Out-of-bounds Read
The software reads data past the end, or before the beginning, of the intended buffer. Typically, this can allow attackers to read sensitive information from other memory locations or cause a crash. A crash can occur when the code reads a variable amount of data and assumes that a sentinel exists to stop the read operation, such as a NUL in a string. The expected sentinel might not be located in the out-of-bounds memory, causing excessive data to be read, leading to a segmentation fault or a buffer overflow. The software may modify an index or perform pointer arithmetic that references a memory location that is outside of the boundaries of the buffer. A subsequent read operation then produces undefined or unexpected results.
Products Associated with CVE-2026-18020
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Affected Versions
IBM i:- Version 7.6 is affected.
- Version 7.5 is affected.
- Version 7.4 is affected.
- Version 7.3 is affected.