Ruby oj: Oj (Optimized JSON) is a JSON parser and Object marshaller packaged as a Ruby gem. (CVE-2026-54899)
Description
Oj (Optimized JSON) is a Ruby gem for JSON parsing and object marshalling. Versions prior to 3.17.2 contain a heap use-after-free vulnerability triggered when disabling symbol_keys on a reused Oj::Parser instance. This occurs because the internal key cache is freed but the pointer is not cleared, leading to use of freed memory on subsequent parses. The issue is fixed in version 3.17.2.
CVSS v4.0
Affected software
pkg:deb/ubuntu/ruby-oj?arch=source&distro=trustypkg:deb/ubuntu/ruby-oj?arch=source&distro=xenialpkg:deb/ubuntu/ruby-oj?arch=source&distro=bionicpkg:deb/ubuntu/ruby-oj?arch=source&distro=focalpkg:deb/ubuntu/ruby-oj?arch=source&distro=jammypkg:deb/ubuntu/ruby-oj?arch=source&distro=noblepkg:deb/ubuntu/ruby-oj?arch=source&distro=questingpkg:deb/ubuntu/ruby-oj?arch=source&distro=stonkingpkg:deb/ubuntu/ruby-oj?arch=source&distro=resoluteRun on your own infrastructure? Check whether these packages are installed with threat-finder — our free open-source scanner.
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
The vulnerability in Oj arises when the symbol_keys option is toggled from true to false on a reused Oj::Parser instance. The internal key cache is freed without clearing its pointer, causing subsequent parse calls to access freed memory, resulting in a heap use-after-free condition. This flaw is present in versions before 3.17.2 and has been addressed in 3.17.2.
Potential Impact
This use-after-free vulnerability can lead to memory corruption, potentially causing application crashes or undefined behavior. The CVSS vector indicates network attack vector with low complexity and partial attack impact on confidentiality and availability, but no privileges or user interaction required. No known exploits are reported in the wild.
Mitigation Recommendations
Upgrade to Oj version 3.17.2 or later where this vulnerability is fixed. No other mitigations are indicated.
Technical Details
- Gcve Source
- db.gcve.eu
- Osv Id
- UBUNTU-CVE-2026-54899
- Osv Schema Version
- 1.7.0
- Ecosystems
- ["Ubuntu:14.04:LTS","Ubuntu:16.04:LTS","Ubuntu:18.04:LTS","Ubuntu:20.04:LTS","Ubuntu:22.04:LTS","Ubuntu:24.04:LTS","Ubuntu:25.10","Ubuntu:26.10","Ubuntu:26.04:LTS"]
- Cvss Version
- 4.0
- State
- PUBLISHED
Threat ID: 6ad3f5f52cdf04f656663535
Added to database: 10/17/2026, 22:25:57 UTC
Last enriched: 10/18/2026, 00:47:22 UTC
Last updated: 10/18/2026, 00:47:22 UTC
Views: 2
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