Denial of service in geth

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

6.5 · CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

EPSS

• CVE-2020-26242: 1.48% estimated exploitation activity in the next 30 days; percentile 73.95 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Impact Denial-of-service (crash) during block processing Details Affected versions suffer from a vulnerability which can be exploited through the MULMOD operation, by specifying a modulo of 0: mulmod(a,b,0), causing a panic in the underlying library. The crash was in the uint256 library, where a buffer underflowed. if d == 0, dLen remains 0 and https://github.com/holiman/uint256/blob/4ce82e695c10ddad57215bdbeafb68b8c5df2c30/uint256.go#L451 will try to access index [-1]. The uint256 library was first merged in this commit, on 2020-06-08. Exploiting this vulnerabilty would cause all vulnerable nodes to drop off the network. The issue was brought to our attention through a bug report, showing a panic occurring on sync from genesis on the Ropsten network. It was estimated that the least obvious way to fix this would be to merge the fix into uint256, make a new release of that library and then update the geth-dependency. - https://github.com/holiman/uint256/releases/tag/v1.1.1 was made…

Published by the source

29 Jun 2021, 21:13 UTC

Last modified by the source

30 Jan 2025, 14:38 UTC

Source last checked

26 Oct 2026, 15:08 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-jm5c-rv3w-w83m

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# Patch Next advisory brief: CVE-2020-26242

Advisory: Denial of service in geth
IDs: CVE-2020-26242, GHSA-jm5c-rv3w-w83m
Record: https://patchnext.com/advisories/cve-2020-26242 (revision 1, source checked 26 Oct 2026, 15:08 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 6.5)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: github.com/holiman/uint256 1.1.1; github.com/ethereum/go-ethereum 1.9.18. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go github.com/holiman/uint256: affected >= 0.1.0, < 1.1.1; fixed in 1.1.1
- Go github.com/ethereum/go-ethereum: affected >= 1.9.16, < 1.9.18; fixed in 1.9.18

## Suggested inspection (read-only)
- Go github.com/holiman/uint256: check the installed version with your package manager.
- Go github.com/ethereum/go-ethereum: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on github.com/holiman/uint256, github.com/ethereum/go-ethereum.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-jm5c-rv3w-w83m (GitHub-reviewed advisory GHSA-jm5c-rv3w-w83m lists affected ranges: Go github.com/ethereum/go-ethereum >=1.9.16 =0.1.0 <1.1.1)

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