# CVE-2026-54899: Oj: Use-After-Free in Oj::Parser Symbol Key Cache Toggle

> A use-after-free vulnerability in the Oj Ruby gem allows attackers to cause crashes or execute code by toggling symbol keys on a reused parser instance.

- **Severity:** Medium 6.3 (`CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:N/VA:L/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 30 Jun 2026
- **Updated:** 1 Jul 2026
- **Also known as:** DEBIAN-CVE-2026-54899, GHSA-2cw7-v8ff-p88r, MINI-2pg7-5c55-2xfc, MINI-3976-3wf6-x2jj, MINI-53jm-38p8-cr98, MINI-695p-3hf6-jh82, MINI-76x7-9x9p-f8x4, MINI-9vg2-rh96-qjh2, MINI-fmx2-fhm7-9g3r, MINI-p9pw-339c-8qv6, MINI-rj24-cj8v-f4vm, MINI-rp98-jr3q-wxxp, UBUNTU-CVE-2026-54899

## What is CVE-2026-54899?

CVE-2026-54899 is a medium-severity use after free vulnerability in ohler55 oj, published on 30 Jun 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

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.

Weakness: CWE-416 (Use After Free)

## Which versions are affected by CVE-2026-54899?

2 open source packages ship an affected version, including oj.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `oj` | RubyGems | All versions | 3.17.2 |
| `oj` | RubyGems | All versions | 3.17.2 |

## How do I fix CVE-2026-54899?

Upgrade oj to 3.17.2 or later.

## Is CVE-2026-54899 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-54899 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-54899 and fix it if it is affected.

What it is: CVE-2026-54899 is a medium-severity use after free vulnerability in ohler55 oj, published on 30 Jun 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-54899 exists.

Affected packages and fixed versions:
- oj (RubyGems): affected all versions; fixed in 3.17.2
- oj (RubyGems): affected all versions; fixed in 3.17.2

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-54899/ (Markdown: https://insights.sbomify.com/CVE-2026-54899/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-54899
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-54899
- OSV: https://osv.dev/vulnerability/CVE-2026-54899

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-54899/
Summaries are generated and may contain mistakes; the official description above is the record.