What’s Vulnerable › Vulnerabilities
CVE-2026-54500: Oj: intern.c form_attr has an uninitialized stack read
- Severity: medium (CVSS 5.3 v3.1)
- Exploited in the wild: not listed in CISA KEV
- EPSS: 0.2% probability of exploitation in the next 30 days
- Public exploit or detection template: none known
- Published: 2026-07-01 · updated 2026-10-25
- Weakness: CWE-125
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.
Affected products
- Rubygems Oj: before 3.17.3; 0.5, 0.5.1, 0.5.2, 0.6.0, 0.7.0, 0.8.0 (+288) — fixed in 3.17.3
- ohler55 oj: before 3.17.3
How to fix
Upgrade to a fixed version: Rubygems Oj 3.17.3. Check the vendor advisory for mitigations.
References
Get alerted when CVE-2026-54500 or the next vulnerability affects your stack