CVE-2026-54500
MediumCVSS 5.3Exploitation Probability (EPSS)
Low risk10th percentile - higher than 10% of all known CVEs
Summary
In the Oj (Optimized JSON) library for Ruby, a vulnerability was found where uninitialized stack memory is read when parsing JSON keys of 254 bytes or longer in :object mode. The flaw occurs in form_attr() which passes a stack buffer instead of a properly allocated heap buffer to rb_intern3(), causing process stack memory disclosure. The issue is fixed in version 3.17.3.
Risk Assessment
An attacker can exploit this vulnerability to read fragments of process stack memory, potentially leaking sensitive data such as keys, passwords, or other information stored in the application's memory.
Recommendation
Immediately update the Oj library to version 3.17.3 or later. If an update is not possible, avoid using :object mode with Oj.load() for untrusted JSON data.
Other vulnerabilities in Oj
See all- CVE-2026-54903Medium
A vulnerability in the Oj (Optimized JSON) library for Ruby prior to version 3.17.2 causes heap corruption when parsing a JSON string longer than 2 GB. An integer overflow in the buf_append_string function leads to copying an astronomically large amount of data out of bounds.
- CVE-2026-54902Medium
The Oj (Optimized JSON) library for Ruby prior to version 3.17.2 has a Use-After-Free vulnerability in SAJ mode. The Oj::Parser does not protect cached object keys (≥35 bytes) from garbage collection, and a Ruby callback in hash_end can free the key memory while the C parser still holds a pointer. This causes a segfault, confirmed by RIP pointing to address 0x4242.
- CVE-2026-54901Medium
A Use-After-Free vulnerability was found in the Oj (Optimized JSON) library for Ruby in normal parser mode. The issue occurs when the garbage collector reclaims array_class and hash_class objects before they are used, leading to dereferencing freed memory and a segfault.
- CVE-2026-54900Medium
In the Oj (Optimized JSON) library for Ruby, a heap corruption vulnerability exists. When a JSON object key is exactly 65,535 bytes long, an integer truncation in the form_attr function causes a negative length to be passed to memcpy, copying a huge amount of data and crashing the process. The issue is fixed in version 3.17.2.
- CVE-2026-54899Medium
A use-after-free vulnerability has been discovered in the Oj (Optimized JSON) library for Ruby. Disabling symbol_keys on a reused Oj::Parser instance frees the internal key cache without clearing the pointer, leading to reading from freed memory during subsequent parsing.
- CVE-2026-54898Low
A heap use-after-free vulnerability exists in the C engine of the Oj (Optimized JSON) Ruby gem prior to version 3.17.2. The issue occurs when a SAJ/SAJ2 callback mutates the input JSON string during parsing, causing the internal buffer to be reallocated and leaving a dangling pointer.
- CVE-2026-54897Low
Oj (Optimized JSON) is a JSON parser and Object marshaller packaged as a Ruby gem. Prior to version 3.17.2, Oj::Doc iterators (each_value, each_child, each_leaf) were vulnerable to a heap use-after-free. When a Ruby block yielded during iteration calls doc.close or d.close, the document's heap memory is freed while the C iterator is still running. When control returns from the block, the iterator reads from the freed region, producing a use-after-free accessible from pure Ruby.
- CVE-2026-54896Low
A heap buffer overflow vulnerability was found in the Oj (Optimized JSON) library for Ruby when serializing Exception objects with a large :indent value. The issue affects versions prior to 3.17.2 and has been fixed in that version.
- CVE-2026-54592High
A denial-of-service (DoS) vulnerability was found in the Oj (Optimized JSON) library for Ruby. The Oj::Doc#each_child function, when recursively processing a deeply nested JSON document, overflows a fixed-size stack buffer, causing a process crash. The issue has been fixed in version 3.17.3.
- CVE-2026-54502Medium
A stack-based buffer overflow vulnerability was found in the Oj (Optimized JSON) library for Ruby in the Oj.dump method. The issue occurs when a large :indent value is provided, causing a 2 GB write to the stack and process crash.
Original NVD description (English source)
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.