CVE-2026-54902 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 SAJ mode does not protect cached object keys (≥ 35 bytes) from garbage collection. A Ruby callback that triggers GC inside hashend can cause the key string to be reclaimed while the C parser still holds a pointer to it. The subsequent access to the freed string VALUE results in a segfault, confirmed by an RIP pointing to address 0x4242 (a canary-style pattern suggesting control over the freed memory's content). Version Software: oj gem Affected: all versions with ext/oj/saj2.c / ext/oj/parser.c Latest tested: 3.17.1 (confirmed present) Details Short keys (≤ 34 bytes) are stored inline on the C stack and are safe. Long keys (≥ 35 bytes) are stored as heap-allocated Ruby String objects passed to rbfuncall as the key argument. Between the key being resolved and the callback completing, a GC triggered inside the callback (e.g. GC.start) can collect the key String, leaving a dangling VALUE. Crash output: The freed VALUE 0x4242 shows the attacker-controlled content of the key string was loaded as a pointer, a classic use-after-free indicator. 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.
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 instead of chasing every advisory.
Kodem's runtime-powered SCA identifies whether CVE-2026-54902 is reachable in your applications. Explore open-source security for your team.
See if CVE-2026-54902 is reachable in your applications. Get a demo
Already deployed Kodem? See CVE-2026-54902 in your environment →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-2026-54902 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-2026-54902 is fixed in 3.17.3. Upgrade to this version or later.
Whether CVE-2026-54902 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.