Summary
tendermint-rs's Light Client Verifier allows malicious validators to spoof votes from other validators
Name: ISA-2025-003: Malicious validator can spoof votes from other validators
Component: tendermint-rs
Criticality: High (Catastrophic Impact; Rare Likelihood per ACMv1.2)
Affected versions: <= v0.40.2
Affected users: Everyone
Description
tendermint-rs contains a critical vulnerability in its light client implementation due to insecure handling of corrupted validator sets. Because it doesn't check that the validator address is correctly derived from the validator's public key when counting votes, it is possible to spoof votes from other validators. The result is being able to construct the malicious block and cheat the light client. The light client will accept such a block, seemingly signed by 2/3+ majority.
Workarounds
There are no known workarounds for this issue.
Timeline
- March 12, 2025, 13:41pm PST: Issue reported
- March 12, 2025, 03:00am PST: Core team completes validation of issue
This issue was reported by Felix Wilhelm from Asymmetric Research.
Impact
The application does not correctly enforce access controls, allowing a principal to access resources or operations beyond their granted permissions. Typical impact: unauthorized data access or execution of privileged operations.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
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The new tendermint-rs release v0.40.3 fixes this issue.
Unreleased code in the main branch is patched as well.
Frequently Asked Questions
- What is GHSA-6JRF-4JV4-R9MW? GHSA-6JRF-4JV4-R9MW is a high-severity incorrect authorization vulnerability in tendermint-light-client-verifier (rust), affecting versions < 0.40.3. It is fixed in 0.40.3. The application does not correctly enforce access controls, allowing a principal to access resources or operations beyond their granted permissions.
- Which versions of tendermint-light-client-verifier are affected by GHSA-6JRF-4JV4-R9MW? tendermint-light-client-verifier (rust) versions < 0.40.3 is affected.
- Is there a fix for GHSA-6JRF-4JV4-R9MW? Yes. GHSA-6JRF-4JV4-R9MW is fixed in 0.40.3. Upgrade to this version or later.
- Is GHSA-6JRF-4JV4-R9MW exploitable, and should I be worried? Whether GHSA-6JRF-4JV4-R9MW is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether GHSA-6JRF-4JV4-R9MW is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix GHSA-6JRF-4JV4-R9MW? Upgrade
tendermint-light-client-verifierto 0.40.3 or later.