Ethereum ABI decoder DoS when parsing ZST

Exploitation

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

CVSS

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

EPSS

No dated EPSS signal available.

As published by the source; long descriptions are shortened.

With this notification I would like to inform about a DoS vector in the Ethereum ABI decoder. We have not yet found a way to exploit this with high impact, still the bug could potentially lead to a DoS in server systems. Feel free to ask about an extension of the embargo period. Trail of Bits is informing you and other vendors as a community service, and so we do not seek a bug bounty on these issues. BUG DESCRIPTION Parsers must be written in a robust way, which avoids for example unrecoverable crashes, misinterpretation, hangs, or excessive resource consumption. The recent news about the aCropalypse bug also highlights that more subtle bugs like blind spots in file formats can lead to serious implications. Sometimes the specifications are at fault and sometimes the implementations. In the case of the Ethereum ABI, I have to blame the specification more than the vulnerable implementations. The specification allows zero-sized-types (ZST), which can cause denial-of-service upon…

Published by the source

24 Nov 2023, 16:54 UTC

Last modified by the source

28 Nov 2024, 05:27 UTC

Source last checked

26 Oct 2026, 13:12 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-rqr8-pxh7-cq3g

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-rqr8-pxh7-cq3g

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# Patch Next advisory brief: GHSA-rqr8-pxh7-cq3g

Advisory: Ethereum ABI decoder DoS when parsing ZST
IDs: GHSA-rqr8-pxh7-cq3g
Record: https://patchnext.com/advisories/ghsa-rqr8-pxh7-cq3g (revision 2, source checked 26 Oct 2026, 13:12 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 4.3)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: eth-abi 4.2.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- PyPI eth-abi: affected < 4.2.0; fixed in 4.2.0

## Suggested inspection (read-only)
- `python -m pip show eth-abi`: prints the installed version. Run with the environment that serves production active.

## 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 eth-abi.
- 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://osv.dev/vulnerability/GHSA-rqr8-pxh7-cq3g (OSV record GHSA-rqr8-pxh7-cq3g lists affected ranges: PyPI eth-abi >=0 <4.2.0 (fixed))
- Verified: https://github.com/advisories/GHSA-rqr8-pxh7-cq3g (GitHub-reviewed advisory GHSA-rqr8-pxh7-cq3g lists affected ranges: PyPI eth-abi >=0 <4.2.0)

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