CVE-2021-21271: Tendermint Core is an open source Byzantine Fault Tolerant (BFT) middleware that takes a state transition mach

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MEDIUM 6.5UPGRADE

CVE-2021-21271 is a medium-severity flaw (CVSS 6.5) affecting tendermint. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Tendermint Core is an open source Byzantine Fault Tolerant (BFT) middleware that takes a state transition machine - written in any programming language - and securely replicates it on many machines. Tendermint 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. This timestamp would be calculated using the same algorithm that is used when a block is created and

Why this priority

No elevated risk signals yet

A fixed release or distro patch exists.

Risk facts

CVSS score	6.5 (Medium)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	Low
User interaction	None
EPSS exploit chance	1.8% (top 22%)
CISA exploited list	No
Weakness	CWE-400
Published	2021-01-26
Last modified	2026-06-17

Publisher (CNA): GitHub, Inc. · Vendor: tendermint

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2021-01-26 21:15 UTCPublished CVE record published
2026-06-17 03:35 UTCUpdated Record last modified

tendermint tendermint UPGRADE

Affected: >= 0.34.0 and <= 0.34.2

Fixed in: newer than 0.34.2

Safe to downgrade to: a release before 0.34.0

1. Check installed version

apt-cache policy tendermint || rpm -q tendermint || tendermint --version

2. UPGRADE to newer than 0.34.2 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade tendermint

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade tendermint

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

3. If no update is available yet, DOWNGRADE to a release before 0.34.0 (Debian / Ubuntu)

apt-cache madison tendermint sudo apt install tendermint=<VERSION_BEFORE_0.34.0> sudo apt-mark hold tendermint

3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list tendermint sudo dnf downgrade tendermint-<VERSION_BEFORE_0.34.0> sudo dnf versionlock add tendermint

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2021-21271?

tendermint: upgrade to newer than 0.34.2. Exact commands for each OS are on this page.

Is CVE-2021-21271 being exploited?

CVE-2021-21271 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2021-21271 affect?

CVE-2021-21271 affects tendermint. Severity is medium (CVSS 6.5). Tendermint Core is an open source Byzantine Fault Tolerant (BFT) middleware that takes a state transition machine - written in any programming language - and securely replicates it on many machines. Tendermint Core v0.34.0 introduced a new

How urgent is CVE-2021-21271?

Priority 42/100. No elevated risk signals yet.

Related CVEs

CVE-2020-5303 LOW 3.1 UPGRADE Tendermint before versions 0.33.3, 0.32.10, and 0.31.12 has a denial-of-service vulnerability
CVE-2020-15091 MEDIUM 6.5 UPGRADE TenderMint from version 0.33.0 and before version 0.33.6 allows block proposers to include signatures for the
CVE-2019-25072 HIGH 7.5 UPGRADE Due to support of Gzip compression in request bodies, as well as a lack of limiting response body sizes, a mal

References

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