Vulnerability · Published Jun 30, 2026 · Assigned by GitHub_M
CVE-2026-54900Oj: Negative-Size memcpy in Oj::Parser create_id Attribute Handling
Medium 6.3
In plain English
A medium-severity integer overflow in oj from ohler55. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.5% (higher than 44% of all known vulnerabilities). Ready-made attack tooling exists: public proof-of-concept code. 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, when in usual mode with create_id enabled, Oj::Parser#parse is vulnerable to heap corruption via a negative-size memcpy. When a JSON object key is exactly 65,535 bytes long, an integer truncation in form_attr (usual.c:63) converts the length to -1 before passing it to memcpy. This causes memcpy to copy SIZE_MAX bytes (interpreted as a huge size_t), corrupting heap memory and crashing the process. The 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-2026-54900 |
| Debian:13 | ruby-oj | 3.16.3-1+deb13u1 | DEBIAN-CVE-2026-54900 |
| Debian:14 | ruby-oj | 3.17.3-1 | DEBIAN-CVE-2026-54900 |
| RubyGems | oj | 3.17.3 | GHSA-9cv6-qcjw-4grx |
| Ubuntu:22.04:LTS | ruby-oj | no fix listed | UBUNTU-CVE-2026-54900 |
| Ubuntu:24.04:LTS | ruby-oj | no fix listed | UBUNTU-CVE-2026-54900 |
| Ubuntu:25.10 | ruby-oj | no fix listed | UBUNTU-CVE-2026-54900 |
| Ubuntu:26.04:LTS | ruby-oj | no fix listed | UBUNTU-CVE-2026-54900 |
| Ubuntu:26.10 | ruby-oj | no fix listed | UBUNTU-CVE-2026-54900 |
Affected products (as reported)
Weakness: CWE-190, CWE-787 · 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-9cv6-qcjw-4grx x_refsource_CONFIRM