CVE-2016-20013: sha256crypt and sha512crypt through 0.6 allow attackers to cause a denial of service (CPU consumption) because

Q: How do I fix CVE-2016-20013?

sha256crypt: upgrade to newer than 0.6; sha512crypt: upgrade to newer than 0.6. Exact commands for each OS are on this page.

Q: Is CVE-2016-20013 being exploited?

CVE-2016-20013 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-2016-20013 affect?

CVE-2016-20013 affects sha256crypt, sha512crypt. Severity is high (CVSS 7.5). sha256crypt and sha512crypt through 0.6 allow attackers to cause a denial of service (CPU consumption) because the algorithm's runtime is proportional to the square of the length of the password.

Q: How urgent is CVE-2016-20013?

Priority 57/100. High severity; Public exploit reference; Remotely exploitable, no login, no user action

This week

HIGH 7.5REMOTEUPGRADEUPGRADE

CVE-2016-20013 is a high-severity flaw (CVSS 7.5) affecting sha256crypt, sha512crypt. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

sha256crypt and sha512crypt through 0.6 allow attackers to cause a denial of service (CPU consumption) because the algorithm's runtime is proportional to the square of the length of the password.

Why this priority

High severity
Public exploit reference
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	2.2% (top 18%)
CISA exploited list	No
Weakness	CWE-770
Published	2022-02-19
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: sha256crypt project · sha512crypt project

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

Am I affected?

Timeline

2022-02-19 05:15 UTCPublished CVE record published
2026-06-17 00:43 UTCUpdated Record last modified

sha256crypt project sha256crypt UPGRADE

Affected: <= 0.6

Fixed in: newer than 0.6

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy sha256crypt || rpm -q sha256crypt || sha256crypt --version

2. UPGRADE to newer than 0.6 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade sha256crypt

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade sha256crypt

Note

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

sha512crypt project sha512crypt UPGRADE

Affected: <= 0.6

Fixed in: newer than 0.6

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy sha512crypt || rpm -q sha512crypt || sha512crypt --version

2. UPGRADE to newer than 0.6 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade sha512crypt

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade sha512crypt

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-2016-20013?

sha256crypt: upgrade to newer than 0.6; sha512crypt: upgrade to newer than 0.6. Exact commands for each OS are on this page.

Is CVE-2016-20013 being exploited?

CVE-2016-20013 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-2016-20013 affect?

CVE-2016-20013 affects sha256crypt, sha512crypt. Severity is high (CVSS 7.5). sha256crypt and sha512crypt through 0.6 allow attackers to cause a denial of service (CPU consumption) because the algorithm's runtime is proportional to the square of the length of the password.

How urgent is CVE-2016-20013?

Priority 57/100. High severity; Public exploit reference; Remotely exploitable, no login, no user action

References

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