Lodestar snappy checksum issue

Exploitation

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

CVSS

not scored

EPSS

No dated EPSS signal available.

As published by the source; long descriptions are shortened.

Impact Unintended permanent chain split affecting greater than or equal to 25% of the network, requiring hard fork (network partition requiring hard fork) Lodestar does not verify checksum in snappy framing uncompressed chunks. Vulnerability Details In Req/Resp protocol the messages are encoded by using sszsnappy encoding, which is a snappy framing compression over ssz encoded message. In snappy framing format there are uncompressed chunks, each such chunk is prefixed with a checksum. Let's see how golang implementation parses such chunks - https://github.com/golang/snappy/blob/master/decode.go#L176 As you can see, if checksum is incorrect, decoder fails and returns error. Now let's look at lodestar decoder https://github.com/ChainSafe/lodestar/blob/unstable/packages/reqresp/src/encodingStrategies/sszSnappy/snappyFrames/uncompress.ts#L17 As you can see, checksum is not verified, bytes are appended to 'result' Proof of Concept How to reproduce: get poc via gist link and run it:

Published by the source

14 Jan 2025, 22:04 UTC

Last modified by the source

14 Jan 2025, 22:04 UTC

Source last checked

26 Oct 2026, 12:31 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-m9c9-mc2h-9wjw

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-m9c9-mc2h-9wjw

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# Patch Next advisory brief: GHSA-m9c9-mc2h-9wjw

Advisory: Lodestar snappy checksum issue
IDs: GHSA-m9c9-mc2h-9wjw
Record: https://patchnext.com/advisories/ghsa-m9c9-mc2h-9wjw (revision 2, source checked 26 Oct 2026, 12:31 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Unrated
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: @lodestar/reqresp 1.25.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm @lodestar/reqresp: affected < 1.25.0; fixed in 1.25.0

## Suggested inspection (read-only)
- `npm ls @lodestar/reqresp --all`: lists every installed copy and version, including transitive ones. Run in the project root after `npm ci`.

## 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 @lodestar/reqresp.
- 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-m9c9-mc2h-9wjw (OSV record GHSA-m9c9-mc2h-9wjw lists affected ranges: npm @lodestar/reqresp >=0 <1.25.0 (fixed))
- Verified: https://github.com/advisories/GHSA-m9c9-mc2h-9wjw (GitHub-reviewed advisory GHSA-m9c9-mc2h-9wjw lists affected ranges: npm @lodestar/reqresp >=0 <1.25.0)

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