{"id":"CVE-2026-54500","aliases":["GHSA-fm7p-mprw-wjm9"],"url":"https://o3.security/vulnerability/CVE-2026-54500","summary":"Oj: intern.c form_attr has an uninitialized stack read","details":"Oj (Optimized JSON) is a JSON parser and Object marshaller packaged as a Ruby gem. In versions prior to 3.17.3, Oj.load in :object mode reads uninitialized stack memory (and, for long keys, reads out of bounds) when parsing a JSON object whose key is 254 bytes or longer. The interned bytes can surface to the caller, disclosing process stack memory. In ext/oj/intern.c, form_attr() handles the long-key path by allocating a heap buffer, `b`, populating it with the attribute name, and then freeing it — but it passed the uninitialized stack buffer buf (not b) to rb_intern3(). rb_intern3 therefore reads len + 1 bytes of uninitialized stack memory. When the key length is >= 256, it also reads out of bounds past the 256-byte buf. The resulting bytes are interned and can reach the caller via the produced Symbol or via the EncodingError message raised on invalid UTF-8, leaking process stack contents. This issue has been fixed in version 3.17.3.","published":"2026-06-30T23:08:28.789Z","modified":"2026-08-12T16:41:13.960734Z","cvss":{"score":5.3,"severity":"MEDIUM","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N"},"epss":{"score":0.00198,"percentile":0.09584,"asOf":"2026-09-07"},"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"RubyGems","name":"oj","fixedVersion":"3.17.3"}],"fix":null,"references":[{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/54xxx/CVE-2026-54500.json"},{"type":"ADVISORY","url":"https://github.com/ohler55/oj/security/advisories/GHSA-fm7p-mprw-wjm9"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-54500"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-12T16:41:13.960734Z"}}