Oj (Optimized JSON) is a JSON parser and Object marshaller packaged as a Ruby gem. In versions prior to 3.17.3, Oj::Doc#each_child, when invoked recursively over a deeply nested JSON document, overflows a fixed-size stack buffer and aborts the process, leading to DoS. In a two-step chain in ext/oj/fast.c, doc_each_child increments doc->where past the where_path[MAX_STACK = 100] array with no bounds check and never restores it (the doc->where-- is missing), so calling each_child recursively from inside the yield block drives doc->where beyond the array. On the next entry the function copies the path into the 800-byte stack-local buffer save_path[MAX_STACK] using wlen = doc->where - doc->where_path, so when the previous recursive call left doc->where past where_path[100] the wlen exceeds MAX_STACK and the memcpy overflows save_path on the C stack; because the Oj::Doc parser imposes no JSON nesting-depth limit (relying on a C-stack pressure check), deeply nested attacker input reaches this path. This issue has been fixed in version 3.17.3.

A flaw was found in Oj, a Ruby gem for JSON parsing. A remote attacker can exploit this vulnerability by providing a deeply nested JSON document. This can lead to a stack buffer overflow in the `Oj::Doc#each_child` function, causing the process to abort and resulting in a denial of service (DoS) for the affected system.

Red Hat's only product shipping the Oj Ruby gem (Compliance Backend) already includes version 3.17.3, which contains the fix for this vulnerability. No Red Hat products are affected. https://www.cve.org/CVERecord?id=CVE-2026-54592 https://nvd.nist.gov/vuln/detail/CVE-2026-54592 https://github.com/ohler55/oj/security/advisories/GHSA-3m6q-jj5j-38c9