CVE-2021-43568: The verify function in the Stark Bank Elixir ECDSA library (ecdsa-elixir) 1.0.0 fails to check that the signat

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CRITICAL 9.8REMOTEDOWNGRADE

CVE-2021-43568 is a critical-severity flaw (CVSS 9.8) affecting elixir ecdsa. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

The verify function in the Stark Bank Elixir ECDSA library (ecdsa-elixir) 1.0.0 fails to check that the signature is non-zero, which allows attackers to forge signatures on arbitrary messages.

Why this priority

Critical severity
Public exploit reference
Remotely exploitable, no login, no user action

No fix is published yet: follow the downgrade or mitigation steps.

Risk facts

CVSS score	9.8 (Critical)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	1.1% (top 36%)
CISA exploited list	No
Weakness	CWE-347
Published	2021-11-09
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: starkbank

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

Am I affected?

Timeline

2021-11-09 22:15 UTCPublished CVE record published
2026-06-17 04:11 UTCUpdated Record last modified

starkbank elixir ecdsa DOWNGRADE

Affected: 1.0.0

Fixed in: no fixed release known

Safe to downgrade to: a release before 1.0.0

1. Check installed version

apt-cache policy elixir-ecdsa || rpm -q elixir-ecdsa || elixir-ecdsa --version

2. No fixed release: DOWNGRADE to a release before 1.0.0 (Debian / Ubuntu)

apt-cache madison elixir-ecdsa sudo apt install elixir-ecdsa=<VERSION_BEFORE_1.0.0> sudo apt-mark hold elixir-ecdsa

2. No fixed release: DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list elixir-ecdsa sudo dnf downgrade elixir-ecdsa-<VERSION_BEFORE_1.0.0> sudo dnf versionlock add elixir-ecdsa

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-2021-43568?

elixir ecdsa: downgrade or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2021-43568 being exploited?

CVE-2021-43568 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-2021-43568 affect?

CVE-2021-43568 affects elixir ecdsa. Severity is critical (CVSS 9.8). The verify function in the Stark Bank Elixir ECDSA library (ecdsa-elixir) 1.0.0 fails to check that the signature is non-zero, which allows attackers to forge signatures on arbitrary messages.

How urgent is CVE-2021-43568?

Priority 60/100. Critical severity; Public exploit reference; Remotely exploitable, no login, no user action

References

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