CVE-2026-54898 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#parse is vulnerable to a heap use-after-free when a SAJ/SAJ2 callback mutates the input JSON string during parsing. The C engine holds a raw const byte * pointer into the Ruby string's internal buffer. If a callback (e.g. hashstart) resizes the string, for example by calling String#replace with a longer value, Ruby reallocates the string buffer and frees the old one. The C parser's pointer is left dangling; the next character read at parser.c:607 is a use-after-free. Version Software: oj gem Affected: all versions with ext/oj/parser.c Latest tested: 3.17.1 (confirmed present) Details ext/oj/parser.c, parserparse → parse: Ruby's String#replace (or <<, gsub!, etc.) can trigger a reallocation of the string's internal buffer if the new content is larger than the embedded capacity, freeing the old buffer that ptr still points to. ASAN report: 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-2026-54898 is reachable in your applications. Explore open-source security for your team.
See if CVE-2026-54898 is reachable in your applications. Get a demo
Already deployed Kodem? See CVE-2026-54898 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-2026-54898 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-2026-54898 is fixed in 3.17.3. Upgrade to this version or later.
Whether CVE-2026-54898 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.