Vulnerability · Published Jun 30, 2026 · Assigned by GitHub_M
CVE-2026-54898Oj: Use-After-Free in Oj::Parser SAJ Callback via Input Mutation
Low 2.1
In plain English
A low-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 0.2% (higher than 10% 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#parse is vulnerable to a heap use-after-free when a SAJ/SAJ2 callback mutates the input JSON string during parsing. The C engine holds a raw const byte * pointer into the Ruby string's internal buffer. If a callback (e.g. hash_start) resizes the string — for example by calling String#replace with a longer value — Ruby reallocates the string buffer and frees the old one. The C parser's pointer is left dangling; the next character read at parser.c:607 is a use-after-free. 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-2026-54898 |
| Debian:13 | ruby-oj | 3.16.3-1+deb13u1 | DEBIAN-CVE-2026-54898 |
| Debian:14 | ruby-oj | 3.17.3-1 | DEBIAN-CVE-2026-54898 |
| RubyGems | oj | 3.17.3 | GHSA-q2gm-54r6-8fwm |
| Ubuntu:22.04:LTS | ruby-oj | no fix listed | UBUNTU-CVE-2026-54898 |
| Ubuntu:24.04:LTS | ruby-oj | no fix listed | UBUNTU-CVE-2026-54898 |
| Ubuntu:25.10 | ruby-oj | no fix listed | UBUNTU-CVE-2026-54898 |
| Ubuntu:26.04:LTS | ruby-oj | no fix listed | UBUNTU-CVE-2026-54898 |
| Ubuntu:26.10 | ruby-oj | no fix listed | UBUNTU-CVE-2026-54898 |
Affected products (as reported)
Weakness: CWE-416 · Vector: CVSS:4.0/AV:L/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-q2gm-54r6-8fwm x_refsource_CONFIRM