CVE-2026-54500 in ohler55
Summary
by MITRE • 07/01/2026
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.
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Analysis
by VulDB Data Team • 07/01/2026
The Oj Ruby gem vulnerability represents a critical memory disclosure issue affecting versions prior to 3.17.3 where the JSON parser's handling of long keys creates exploitable conditions through improper memory management. This flaw occurs specifically in :object mode when parsing JSON objects with keys exceeding 254 bytes in length, creating a pathway for uninitialized stack memory to be exposed to application callers. The vulnerability stems from the form_attr() function in ext/oj/intern.c which manages the long-key processing path by allocating heap buffers but incorrectly passing uninitialized stack memory to rb_intern3() function.
The technical implementation of this vulnerability involves multiple memory access patterns that compound the security risk. When processing keys of 254 bytes or longer, the system allocates a heap buffer 'b' to store the attribute name but fails to properly utilize this allocated memory. Instead, it passes the uninitialized stack buffer 'buf' to rb_intern3(), which then reads len + 1 bytes of uninitialized stack memory during symbol internment operations. This behavior becomes particularly dangerous when key lengths reach or exceed 256 bytes, as the code reads beyond the allocated 256-byte buffer boundaries into adjacent stack memory regions, creating predictable memory leaks.
The operational impact of this vulnerability extends beyond simple information disclosure, as it can potentially expose sensitive process memory contents including cryptographic keys, session tokens, and other confidential data stored on the stack. The leaked memory fragments can surface through returned Symbol objects or during EncodingError message generation when invalid UTF-8 sequences are encountered, making this issue particularly concerning for applications processing untrusted JSON input. This vulnerability aligns with CWE-125: Uninitialized Memory Read and represents a classic case of improper memory handling that violates secure coding practices.
The exploitation potential of this vulnerability increases significantly in environments where sensitive data might be present on the stack at the time of parsing operations, particularly in applications that handle authentication tokens, encryption keys, or other security-critical information. Attackers could leverage this issue to extract process memory contents through carefully crafted JSON payloads containing long keys, potentially compromising application security and data confidentiality. Organizations should consider implementing input validation measures and monitoring for unusual memory access patterns as additional defensive controls.
This vulnerability demonstrates the importance of proper memory management in parsing libraries and highlights the need for comprehensive testing of edge cases in input handling. The fix implemented in version 3.17.3 addresses the core issue by ensuring that only properly initialized buffers are passed to memory operations, preventing the exposure of uninitialized stack contents. Security practitioners should prioritize updating affected systems and implementing runtime monitoring to detect potential exploitation attempts. The vulnerability also relates to ATT&CK technique T1059.007: Command and Scripting Interpreter: Python, as similar memory corruption issues could enable privilege escalation or information gathering through modified input processing behaviors in Ruby applications.