{"id":"CVE-2021-21271","aliases":["GHSA-p658-8693-mhvg","GO-2022-1052"],"url":"https://o3.security/vulnerability/CVE-2021-21271","summary":"Tendermint Core vulnerable to Uncontrolled Resource Consumption","details":"### Description \n\nTendermint Core v0.34.0 introduced a new way of handling evidence of misbehavior. As part of this, [we added a new `Timestamp` field to `Evidence` structs](https://github.com/tendermint/tendermint/pull/5219). This timestamp would be calculated using the same algorithm that is used when a block is created and proposed. (This algorithm relies on the timestamp of the last commit from this specific block.) \n\nIn Tendermint Core v0.34.0-v0.34.2, the `consensus` reactor is responsible for forming `DuplicateVoteEvidence` whenever double signs are observed. However, the current block is still “in flight” when it is being formed by the `consensus` reactor. It hasn’t been finalized through network consensus yet. This means that different nodes in the network may observe different “last commits” when assigning a timestamp to `DuplicateVoteEvidence.`\n\nIn turn, different nodes could form `DuplicateVoteEvidence` objects at the same height but with different timestamps. One `DuplicateVoteEvidence` object (with one timestamp) will then eventually get finalized in the block, but this means that any `DuplicateVoteEvidence` with a different timestamp is considered invalid. Any node that formed invalid `DuplicateVoteEvidence` will continue to propose invalid evidence; its peers may see this, and choose to disconnect from this node. This bug means that double signs are DoS vectors in Tendermint Core v0.34.0-v0.34.2. \n\nTendermint Core v0.34.3 is a security release which fixes this bug. As of v0.34.3, `DuplicateVoteEvidence` is no longer formed by the `consensus` reactor; rather, the `consensus` reactor passes the `Vote`s themselves into the `EvidencePool`, which is now responsible for forming `DuplicateVoteEvidence`. The `EvidencePool` has timestamp info that should be consistent across the network, which means that `DuplicateVoteEvidence` formed in this reactor should have consistent timestamps. \n\nThis release changes the API between the `consensus` and `evidence` reactors. \n\n### Impact\n\nThis is a denial-of-service vector which impacts networks running Tendermint Core v0.34.0 - v0.34.2.\n\n### Remediation\n\nThis problem has been patched in Tendermint Core v0.34.3. Networks running impacted versions of Tendermint Core should update immediately.\n\n### Workarounds\n\nThere are no workarounds, other than upgrading to a patched version of Tendermint Core.\n\n### Credits \n\n* Crypto.com (@cyril-crypto, @brianatcrypto, @tomtau and  @yihuang) for finding and submitting this vulnerability\n* @melekes and @cmwaters for identifying the root cause and patching the problem \n\n### For more information\n\nIf you have any questions or comments about this advisory:\n* Open an issue in [tendermint/tendermint](https://github.com/tendermint/tendermint)\n* Email us at [security@tendermint.com](mailto:security@tendermint.com)","published":"2021-01-26T21:15:12.503Z","modified":"2026-07-09T00:21:05.597461Z","cvss":{"score":6.5,"severity":"MEDIUM","vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H"},"epss":{"score":0.01742,"percentile":0.76646,"asOf":"2026-09-17"},"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"Go","name":"github.com/tendermint/tendermint","fixedVersion":"0.34.3"}],"fix":{"url":"https://github.com/tendermint/tendermint/commit/a2a6852ab99e4a0f9e79f0ea8c1726e262e25c76","label":"tendermint/tendermint@a2a6852"},"references":[{"type":"ADVISORY","url":"https://github.com/tendermint/tendermint/blob/v0.34.3/CHANGELOG.md#v0.34.3"},{"type":"ADVISORY","url":"https://github.com/tendermint/tendermint/security/advisories/GHSA-p658-8693-mhvg"},{"type":"FIX","url":"https://github.com/tendermint/tendermint/commit/a2a6852ab99e4a0f9e79f0ea8c1726e262e25c76"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2021-21271"},{"type":"WEB","url":"https://github.com/tendermint/tendermint/pull/5219"},{"type":"PACKAGE","url":"https://github.com/tendermint/tendermint"},{"type":"WEB","url":"https://pkg.go.dev/vuln/GO-2022-1052"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-07-09T00:21:05.597461Z"}}