Signature verification failure in Tendermint

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.

The root cause of this security vulnerability is in the Tendermint specification, and this advisory is a duplicate of https://github.com/tendermint/spec/security/advisories/GHSA-jqfc-687g-59pw. Impact Tendermint light clients running versions 0.34.0 to 0.34.8 are unable to detect and punish a new kind of attack. We’re calling this a “forward lunatic attack,” or FLA. The severity of this vulnerability is moderate. Note that an FLA cannot be successfully executed unless there are already ⅓+ Byzantine validators, and therefore outside of Tendermint’s security model; however, it is important to be able to detect and punish these kinds of attacks in order to incentivize correct behavior. In an FLA, an attacking validator (with ⅓+ voting power) signs commit messages for arbitrary application state associated with a block height that hasn’t been seen yet, hence the name “forward lunatic attacks.” A malicious validator effectively executes a lunatic attack, but signs messages for a target…

Published by the source

20 Dec 2021, 18:17 UTC

Last modified by the source

20 Jun 2023, 11:56 UTC

Source last checked

26 Oct 2026, 14:58 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-f3w5-v9xx-rp8p

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# Patch Next advisory brief: GHSA-f3w5-v9xx-rp8p

Advisory: Signature verification failure in Tendermint
IDs: GHSA-f3w5-v9xx-rp8p
Record: https://patchnext.com/advisories/ghsa-f3w5-v9xx-rp8p (revision 1, source checked 26 Oct 2026, 14:58 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: github.com/tendermint/tendermint 0.34.9. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go github.com/tendermint/tendermint: affected >= 0.34.0, < 0.34.9; fixed in 0.34.9

## Suggested inspection (read-only)
- Go github.com/tendermint/tendermint: 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/tendermint/tendermint.
- 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-f3w5-v9xx-rp8p (GitHub-reviewed advisory GHSA-f3w5-v9xx-rp8p lists affected ranges: Go github.com/tendermint/tendermint >=0.34.0 <0.34.9)

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