CVE-2026-54899: OHLER55 Oj

Medium severity, CVSS 6.3. EPSS: 0.3% chance of exploitation in the next 30 days.

Oj (Optimized JSON) is a JSON parser and Object marshaller packaged as a Ruby gem. Prior to version 3.17.2, disabling symbol_keys on a reused Oj::Parser instance triggers a heap use-after-free. When symbol_keys is toggled from true to false, opt_symbol_keys_set frees the internal key cache (cache_free) but does not clear the pointer. The next parse call reads from the freed cache via cache_intern, producing a use-after-free. This issue has been fixed in version 3.17.2.

Affected products

• OHLER55 Oj: before 3.17.2 (fixed in 3.17.2)

Published 2026-07-01. Last modified 2026-07-01.