CVE-2022-21685: Integer underflow in Frontier

Severity: medium (CVSS 6.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 1.3% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2022-01-14 · updated 2026-06-17
Weakness: CWE-191

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 products

paritytech frontier: through 2022-01-13

References

https://github.com/paritytech/frontier/commit/8a93fdc6c9f4eb1d2f2a11b7ff1d12d70bf5a664
https://github.com/paritytech/frontier/pull/549
https://github.com/paritytech/frontier/security/advisories/GHSA-cjg2-2fjg-fph4
https://github.com/paritytech/frontier/commit/8a93fdc6c9f4eb1d2f2a11b7ff1d12d70bf5a664
https://github.com/paritytech/frontier/pull/549
https://github.com/paritytech/frontier/security/advisories/GHSA-cjg2-2fjg-fph4

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