CVE-2020-15091: TenderMint from version 0.33.0 and before version 0.33.6 allows block proposers to include signatures for the

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MEDIUM 6.5UPGRADE

CVE-2020-15091 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 from version 0.33.0 and before version 0.33.6 allows block proposers to include signatures for the wrong block. This may happen naturally if you start a network, have it run for some time and restart it (**without changing chainID**). A malicious block proposer (even with a minimal amount of stake) can use this vulnerability to completely halt the network. This issue is fixed in Tendermint 0.33.6 which checks all the signatures are for

Why this priority

Public exploit reference

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	0.9% (top 40%)
CISA exploited list	No
Weakness	CWE-347
Published	2020-07-02
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

2020-07-02 17:15 UTCPublished CVE record published
2026-06-17 02:56 UTCUpdated Record last modified

tendermint tendermint UPGRADE

Affected: >= 0.33.0 and < 0.33.6

Fixed in: 0.33.6

Safe to downgrade to: a release before 0.33.0

1. Check installed version

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

2. UPGRADE to 0.33.6 (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 0.33.0 (Debian / Ubuntu)

apt-cache madison tendermint sudo apt install tendermint=<VERSION_BEFORE_0.33.0> 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_0.33.0> 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-2020-15091?

tendermint: upgrade to 0.33.6. Exact commands for each OS are on this page.

Is CVE-2020-15091 being exploited?

CVE-2020-15091 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-2020-15091 affect?

CVE-2020-15091 affects tendermint. Severity is medium (CVSS 6.5). TenderMint from version 0.33.0 and before version 0.33.6 allows block proposers to include signatures for the wrong block. This may happen naturally if you start a network, have it run for some time and restart it (**without changing chainI

How urgent is CVE-2020-15091?

Priority 43/100. Public exploit reference

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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
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References

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