CVE-2022-21685 is a medium-severity (CVSS 6.5) CWE-191 vulnerability in pallet-evm-precompile-modexp. O3 Security confirms whether CVE-2022-21685 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
Integer underflow in Frontier
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-2022-21685 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 0 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
pallet-evm-precompile-modexpReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects crates.io packages — download data is not available via public APIs for these ecosystems.
Description
Frontier is Substrate's Ethereum compatibility layer. Prior to commit number 8a93fdc6c9f4eb1d2f2a11b7ff1d12d70bf5a664, a bug in Frontier's MODEXP precompile implementation can cause an integer underflow in certain conditions. This will cause a node crash for debug builds. For release builds (and production WebAssembly binaries), the impact is limited as it can only cause a normal EVM out-of-gas. Users who do not use MODEXP precompile in their runtime are not impacted. A patch is available in pull request #549.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🦀crates.io | pallet-evm-precompile-modexp | all versions | No fix |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for pallet-evm-precompile-modexp. 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.
Remediation status
No patched version of pallet-evm-precompile-modexp has shipped for CVE-2022-21685 yet. Where your build allows, override or pin the dependency away from the vulnerable range, and apply any maintainer-recommended mitigation.
Mitigate without a patch
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-2022-21685 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-2022-21685. 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-2022-21685 in your dependencies?
O3 detects CVE-2022-21685 across crates.io dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.