CVE-2021-45699: An issue was discovered in the ckb crate before 0.40.0 for Rust

Q: How do I fix CVE-2021-45699?

ckb: upgrade to 0.40.0. Exact commands for each OS are on this page.

Q: Is CVE-2021-45699 being exploited?

CVE-2021-45699 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2021-45699 affect?

CVE-2021-45699 affects ckb. Severity is high (CVSS 7.5). An issue was discovered in the ckb crate before 0.40.0 for Rust. Remote attackers may be able to conduct a 51% attack against the Nervos CKB blockchain by triggering an inability to allocate memory for the misbehavior HashMap.

Q: How urgent is CVE-2021-45699?

Priority 50/100. High severity; Remotely exploitable, no login, no user action

This month

HIGH 7.5REMOTEUPGRADE

CVE-2021-45699 is a high-severity flaw (CVSS 7.5) affecting ckb. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

An issue was discovered in the ckb crate before 0.40.0 for Rust. Remote attackers may be able to conduct a 51% attack against the Nervos CKB blockchain by triggering an inability to allocate memory for the misbehavior HashMap.

Why this priority

High severity
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	7.5 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	1.5% (top 26%)
CISA exploited list	No
Weakness	CWE-770
Published	2021-12-27
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: nervos

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

Am I affected?

Timeline

2021-12-27 00:15 UTCPublished CVE record published
2026-06-17 04:13 UTCUpdated Record last modified

nervos ckb UPGRADE

Affected: < 0.40.0

Fixed in: 0.40.0

Safe to downgrade to: no unaffected older release

1. Check installed version

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

2. UPGRADE to 0.40.0 (Debian / Ubuntu)

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

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade ckb

Note

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

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-2021-45699?

ckb: upgrade to 0.40.0. Exact commands for each OS are on this page.

Is CVE-2021-45699 being exploited?

CVE-2021-45699 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-2021-45699 affect?

CVE-2021-45699 affects ckb. Severity is high (CVSS 7.5). An issue was discovered in the ckb crate before 0.40.0 for Rust. Remote attackers may be able to conduct a 51% attack against the Nervos CKB blockchain by triggering an inability to allocate memory for the misbehavior HashMap.

How urgent is CVE-2021-45699?

Priority 50/100. High severity; Remotely exploitable, no login, no user action

Related CVEs

CVE-2021-45700 HIGH 7.5 UPGRADE An issue was discovered in the ckb crate before 0.40.0 for Rust
CVE-2021-45698 CRITICAL 9.8 UPGRADE An issue was discovered in the ckb crate before 0.40.0 for Rust

References

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