CVE-2006-0591: The crypt_gensalt functions for BSDI-style extended DES-based and FreeBSD-sytle MD5-based password hashes in c

Routine

LOW 1.2DOWNGRADE

CVE-2006-0591 is a low-severity flaw (CVSS 1.2) affecting crypt blowfish. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

The crypt_gensalt functions for BSDI-style extended DES-based and FreeBSD-sytle MD5-based password hashes in crypt_blowfish 0.4.7 and earlier do not evenly and randomly distribute salts, which makes it easier for attackers to guess passwords from a stolen password file due to the increased number of collisions.

Why this priority

No elevated risk signals yet

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

Risk facts

CVSS score	1.2 (Low)
EPSS exploit chance	0.4% (top 67%)
CISA exploited list	No
Weakness	CWE-310
Published	2006-02-08
Last modified	2026-06-16

Publisher (CNA): MITRE · Vendor: solar designer

Last updated 2026-06-16 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2006-02-08 01:02 UTCPublished CVE record published
2026-06-16 22:20 UTCUpdated Record last modified

solar designer crypt blowfish DOWNGRADE

Affected: 0.4.7

Fixed in: no fixed release known

Safe to downgrade to: a release before 0.4.7

1. Check installed version

apt-cache policy crypt-blowfish || rpm -q crypt-blowfish || crypt-blowfish --version

2. No fixed release: DOWNGRADE to a release before 0.4.7 (Debian / Ubuntu)

apt-cache madison crypt-blowfish sudo apt install crypt-blowfish=<VERSION_BEFORE_0.4.7> sudo apt-mark hold crypt-blowfish

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

dnf --showduplicates list crypt-blowfish sudo dnf downgrade crypt-blowfish-<VERSION_BEFORE_0.4.7> sudo dnf versionlock add crypt-blowfish

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-2006-0591?

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

Is CVE-2006-0591 being exploited?

CVE-2006-0591 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-2006-0591 affect?

CVE-2006-0591 affects crypt blowfish. Severity is low (CVSS 1.2). The crypt_gensalt functions for BSDI-style extended DES-based and FreeBSD-sytle MD5-based password hashes in crypt_blowfish 0.4.7 and earlier do not evenly and randomly distribute salts, which makes it easier for attackers to guess password

How urgent is CVE-2006-0591?

Priority 13/100. No elevated risk signals yet.

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References

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