Mezo: ERC-20 bridgeOut burn can be erased by a stale StateDB overwrite leading to full L1 bridge drain

Exploitation

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

CVSS 4.0

8.8 · CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:H/SC:N/SI:N/SA:N · score source

EPSS

No dated EPSS signal available.

As published by the source; long descriptions are shortened.

Note: the fixed version of the validator client has been deployed for some time. Impact Potential full drain of L1 bridge without changing bridged balance on Mezo. Brief/Intro A malicious user can steal all ERC-20 tokens locked in the L1 bridge by repeatedly calling the bridgeOut precompile from a crafted contract. The precompile's ERC-20 burn executes in an inner StateDB that commits to a cache context, but the outer StateDB still holds stale pre-burn storage slots in its dirtyStorage. When the outer transaction commits, it overwrites the inner burn with stale values -- restoring the attacker's balance and allowance while the AssetsUnlocked event has already been persisted to the bridge store. The Ethereum sidecar observes this event and attests the unlock on L1, releasing real tokens to the attacker. The attacker keeps their Mezo balance intact and can repeat the drain every block. Vulnerability Details Mezo's EVM uses a dual-context state architecture for precompile calls. When a…

Published by the source

6 May 2026, 19:57 UTC

Last modified by the source

6 May 2026, 19:57 UTC

Source last checked

26 Oct 2026, 15:19 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-6447-269v-g68m

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# Patch Next advisory brief: GHSA-6447-269v-g68m

Advisory: Mezo: ERC-20 bridgeOut burn can be erased by a stale StateDB overwrite leading to full L1 bridge drain
IDs: GHSA-6447-269v-g68m
Record: https://patchnext.com/advisories/ghsa-6447-269v-g68m (revision 1, source checked 26 Oct 2026, 15:19 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 8.8)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: github.com/mezo-org/mezod 8.0.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go github.com/mezo-org/mezod: affected <= 7.0.0; fixed in 8.0.0

## Suggested inspection (read-only)
- Go github.com/mezo-org/mezod: 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/mezo-org/mezod.
- 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-6447-269v-g68m (GitHub-reviewed advisory GHSA-6447-269v-g68m lists affected ranges: Go github.com/mezo-org/mezod >=0 <=7.0.0)

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