Oj: Stack Buffer Overflow in Oj::Doc#each_child via Deeply Nested Input
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.
Problem Types
| Type | CWE ID | Description |
|---|
| CWE | CWE-125 | CWE-125: Out-of-bounds Read |
| CWE | CWE-787 | CWE-787: Out-of-bounds Write |
Type: CWE
Description: CWE-125: Out-of-bounds Read
Type: CWE
Description: CWE-787: Out-of-bounds Write
Metrics
| Version | Base score | Base severity | Vector |
|---|
| 3.1 | 7.5 | HIGH | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H |
Version: 3.1
Base score: 7.5
Base severity: HIGH
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H