CVE-2026-54899
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.
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Exploitation outlook
- Low exploitation risk0.43% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 35% of all EPSS-scored CVEs.
Advisory coverage (1)
External references
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[](https://www.csirts.com/cve/CVE-2026-54899)