{"id":"CVE-2026-54899","aliases":[],"url":"https://o3.security/vulnerability/CVE-2026-54899","summary":"Oj: Use-After-Free in Oj::Parser Symbol Key Cache Toggle","details":"### Summary\n\nDisabling `symbol_keys` on a reused `Oj::Parser` instance triggers a heap use-after-free. When `symbol_keys` is toggled from `true` to `false`, `opt_symbol_keys_set` frees the internal key cache (`cache_free`) but does not clear the pointer. The next `parse` call reads from the freed cache via `cache_intern`, producing a use-after-free.\n\n### Version\n\n- **Software**: oj gem\n- **Affected**: all versions with `ext/oj/usual.c`\n- **Latest tested**: 3.17.1 (confirmed present)\n\n### Details\n\n`ext/oj/usual.c`, `opt_symbol_keys_set`:\n\n```c\n// usual.c:1043–1051\nif (symbol_keys) {\n    d->key_cache = cache_create(...);   // allocate\n} else {\n    cache_free(d->key_cache);           // free — but d->key_cache pointer not NULLed\n}\n```\n\nOn the next parse call, `cache_key` → `cache_intern` reads from `d->key_cache` which now points to freed memory.\n\nASAN report:\n```\n==145265==ERROR: AddressSanitizer: heap-use-after-free on address 0x50b00001a318\nREAD of size 8 at 0x50b00001a318 thread T0\n    #0 cache_intern            /ext/oj/cache.c:328\n    #1 cache_key               /ext/oj/usual.c:161\n    #2 close_object            /ext/oj/usual.c:285\n    #3 parse                   /ext/oj/parser.c:693\n    #4 parser_parse            /ext/oj/parser.c:1408\nfreed by thread T0 here:\n    #0 free\n    #1 cache_free              /ext/oj/cache.c:277\n    #2 opt_symbol_keys_set     /ext/oj/usual.c:1051\n    #3 option                  /ext/oj/usual.c:1111\n    #4 parser_missing          /ext/oj/parser.c:1362\n0x50b00001a318 is 40 bytes inside freed 112-byte region [fd]fd fd fd fd fd fd fd\n```\n\n### Reproduce\n\n```ruby\nrequire 'oj'\np = Oj::Parser.new(:usual, symbol_keys: true)\np.symbol_keys = false     # frees cache without nulling pointer\np.parse('{\"attacker\":1}') # UAF: reads freed cache\n```","published":"2026-06-19T19:34:30Z","modified":"2026-10-06T20:00:05.191640486Z","cvss":null,"epss":{"score":0.00428,"percentile":0.36409,"asOf":"2026-09-16"},"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"RubyGems","name":"oj","fixedVersion":"3.17.2"}],"fix":null,"references":[{"type":"WEB","url":"https://github.com/ohler55/oj/security/advisories/GHSA-2cw7-v8ff-p88r"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-54899"},{"type":"PACKAGE","url":"https://github.com/ohler55/oj"},{"type":"WEB","url":"https://github.com/rubysec/ruby-advisory-db/blob/master/gems/oj/CVE-2026-54899.yml"},{"type":"WEB","url":"https://www.cve.org/CVERecord/SearchResults?query=CVE-2026-54899"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-10-06T20:00:05.191640486Z"}}