Vulnerability · Published Jun 30, 2026 · Assigned by GitHub_M
CVE-2026-54901Oj: Use-After-Free in Oj::Parser array_class/hash_class GC Marking
Medium 6.3
In plain English
A medium-severity use-after-free in oj from ohler55. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.4% (higher than 35% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official description
Oj (Optimized JSON) is a JSON parser and Object marshaller packaged as a Ruby gem. In versions prior to 3.17.2, Oj::Parser in usual mode does not mark array_class and hash_class references during garbage collection, leading to Use-After-Free. If GC runs after the class is assigned but before a parse, the class object is reclaimed, leaving the parser holding a dangling VALUE. The subsequent parse call dereferences the freed object, producing a segfault. This issue has been fixed in version 3.17.2.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian:12 | ruby-oj | 3.14.2-1+deb12u1 | DEBIAN-CVE-2026-54901 |
| Debian:13 | ruby-oj | 3.16.3-1+deb13u1 | DEBIAN-CVE-2026-54901 |
| Debian:14 | ruby-oj | 3.17.3-1 | DEBIAN-CVE-2026-54901 |
| RubyGems | oj | 3.17.3 | GHSA-vwm4-62gf-x745 |
| Ubuntu:22.04:LTS | ruby-oj | no fix listed | UBUNTU-CVE-2026-54901 |
| Ubuntu:24.04:LTS | ruby-oj | no fix listed | UBUNTU-CVE-2026-54901 |
| Ubuntu:25.10 | ruby-oj | no fix listed | UBUNTU-CVE-2026-54901 |
| Ubuntu:26.04:LTS | ruby-oj | no fix listed | UBUNTU-CVE-2026-54901 |
| Ubuntu:26.10 | ruby-oj | no fix listed | UBUNTU-CVE-2026-54901 |
Affected products (as reported)
Weakness: CWE-416 · Vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N
References
- https://github.com/ohler55/oj/security/advisories/GHSA-vwm4-62gf-x745 x_refsource_CONFIRM