CVE-2026-54500: ohler55 oj Out-of-bounds Read

Vulnerability summary

CVE-2026-54500 is a medium (CVSS 5.3) Out-of-bounds Read vulnerability in ohler55 oj. EPSS estimates a 0.20% chance of exploitation in the next 30 days, higher than 8.9% of scored vulnerabilities.

Timeline

1. 30-06-2026
   PublishedVulnerability first disclosed.
2. 01-07-2026
   Last modifiedVulnerability information updated.

Description

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.

• CWE-125Out-of-bounds ReadThe product reads data past the end, or before the beginning, of the intended buffer.
• CWE-908Use of Uninitialized ResourceThe product uses or accesses a resource that has not been initialized.