CVE-2022-21685Network attack vector

Authenticated debug-node crash via MODEXP gas underflow

Published Jan 14, 2022 · Updated Apr 23, 2025

Integer underflow in Parity Technologies Frontier before commit 8a93fdc allows remote authenticated users to crash debug nodes via MODEXP input. The MODEXP gas-cost calculation subtracts one from the bit length of a zero exponent before adding the length term, underflowing its iteration count. Only runtimes using MODEXP are affected; release builds and production WebAssembly return ordinary EVM out-of-gas instead of crashing.

CVSS severity6.5
Medium
EPSS probability1.33%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Integer underflow in Parity Technologies Frontier before commit 8a93fdc allows remote authenticated users to crash debug nodes via MODEXP input. The MODEXP gas-cost calculation subtracts one from the bit length of a zero exponent before adding the length term, underflowing its iteration count. Only runtimes using MODEXP are affected; release builds and production WebAssembly return ordinary EVM out-of-gas instead of crashing.

The record

CVE
CVE-2022-21685
Published
Jan 14, 2022
Updated
Apr 23, 2025
Vendor
Parity Technologies
Product
Frontier
Classifications
CWE-191, T1499.004
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Jan 14, 2022CVE publishedPublication date reported by the CVE source.
  2. Apr 23, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 8a93fdc

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Parity Technologies · Frontierversion=< 8a93fdc

Published CVSS scores

6.5GitHub, Inc.CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
4.0NIST NVDAV:N/AC:L/Au:S/C:N/I:N/A:P

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-191Integer Underflow (Wrap or Wraparound)
T1499.004Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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