CVE-2026-54901 is a high-severity use after free vulnerability in oj (rubygems), affecting versions < 3.17.2. It is fixed in 3.17.3.
Summary Oj::Parser in usual mode does not mark arrayclass and hashclass references during garbage collection. If GC runs after the class is assigned but before a parse, the class object is reclaimed, leaving the parser holding a dangling VALUE. The subsequent parse call dereferences the freed object, producing a segfault. Version Software: oj gem Affected: all versions with ext/oj/usual.c / ext/oj/parser.c Latest tested: 3.17.1 (confirmed present) Details The parsermark function in ext/oj/parser.c is registered as the GC mark callback for the parser's TypedData. If arrayclass (stored as d->arrayclass in the Usual struct) is not passed to rbgcmark, the GC does not know it is referenced and may collect it. When closearrayclass (usual.c:405) later calls rbfuncallv on the collected class VALUE, it accesses freed memory, crashing at RIP: 0x7f... / 0x0000000000000000. Crash output: Reproduce
Memory is accessed after it has been freed, leading to undefined behavior in native code. Typical impact: memory corruption, crash, or potential code execution.
rubygems
oj (< 3.17.2)oj → 3.17.3 (rubygems)Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
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Upgrade oj to 3.17.3 or later to resolve this vulnerability.
Kodem Kai can prioritize this vulnerability in your dependency tree and generate a fix recommendation.
CVE-2026-54901 is a high-severity use after free vulnerability in oj (rubygems), affecting versions < 3.17.2. It is fixed in 3.17.3. Memory is accessed after it has been freed, leading to undefined behavior in native code.
oj (rubygems) versions < 3.17.2 is affected.
Yes. CVE-2026-54901 is fixed in 3.17.3. Upgrade to this version or later.
Whether CVE-2026-54901 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
Upgrade oj to 3.17.3 or later.