CVE-2026-54592
HIGHCVE-2026-54592 is a high-severity (CVSS 7.5) Out-of-bounds Read vulnerability in oj. O3 Security confirms whether CVE-2026-54592 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
Oj: Stack Buffer Overflow in Oj::Doc#each_child via Deeply Nested Input
Exploitation Status
Proof-of-concept exploit code exists
- CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-54592.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
CVE-2026-54592 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 359,229 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
ojReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects RubyGems packages — download data is not available via public APIs for these ecosystems.
Description
Oj (Optimized JSON) is a JSON parser and Object marshaller packaged as a Ruby gem. In versions prior to 3.17.3, Oj::Doc#each_child, when invoked recursively over a deeply nested JSON document, overflows a fixed-size stack buffer and aborts the process, leading to DoS. In a two-step chain in ext/oj/fast.c, doc_each_child increments doc->where past the where_path[MAX_STACK = 100] array with no bounds check and never restores it (the doc->where-- is missing), so calling each_child recursively from inside the yield block drives doc->where beyond the array. On the next entry the function copies the path into the 800-byte stack-local buffer save_path[MAX_STACK] using wlen = doc->where - doc->where_path, so when the previous recursive call left doc->where past where_path[100] the wlen exceeds MAX_STACK and the memcpy overflows save_path on the C stack; because the Oj::Doc parser imposes no JSON nesting-depth limit (relying on a C-stack pressure check), deeply nested attacker input reaches this path. This issue has been fixed in version 3.17.3.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 💎RubyGems | oj | all versions | 3.17.3 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for oj. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update oj to 3.17.3 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-54592 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether CVE-2026-54592 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to CVE-2026-54592. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2026-54592 in your dependencies?
O3 detects CVE-2026-54592 across RubyGems dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.