CVE-2006-1721: digestmd5.c in the CMU Cyrus Simple Authentication and Security Layer (SASL) library 2.1.18, and possibly othe

Routine

LOW 2.6DOWNGRADE

CVE-2006-1721 is a low-severity flaw (CVSS 2.6) affecting sasl. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

digestmd5.c in the CMU Cyrus Simple Authentication and Security Layer (SASL) library 2.1.18, and possibly other versions before 2.1.21, allows remote unauthenticated attackers to cause a denial of service (segmentation fault) via malformed inputs in DIGEST-MD5 negotiation.

Why this priority

No elevated risk signals yet

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

Risk facts

CVSS score	2.6 (Low)
EPSS exploit chance	2.5% (top 15%)
CISA exploited list	No
Weakness	CWE-20
Published	2006-04-11
Last modified	2026-06-16

Publisher (CNA): MITRE · Vendor: cyrus

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

Am I affected?

Timeline

2006-04-11 23:02 UTCPublished CVE record published
2026-06-16 22:23 UTCUpdated Record last modified

cyrus sasl DOWNGRADE

Affected: 2.1.18 · 2.1.18_r1 · 2.1.18_r2 · 2.1.19 · 2.1.20

Fixed in: no fixed release known

Safe to downgrade to: a release before 2.1.18

1. Check installed version

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

2. No fixed release: DOWNGRADE to a release before 2.1.18 (Debian / Ubuntu)

apt-cache madison sasl sudo apt install sasl=<VERSION_BEFORE_2.1.18> sudo apt-mark hold sasl

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

dnf --showduplicates list sasl sudo dnf downgrade sasl-<VERSION_BEFORE_2.1.18> sudo dnf versionlock add sasl

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-2006-1721?

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

Is CVE-2006-1721 being exploited?

CVE-2006-1721 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-2006-1721 affect?

CVE-2006-1721 affects sasl. Severity is low (CVSS 2.6). digestmd5.c in the CMU Cyrus Simple Authentication and Security Layer (SASL) library 2.1.18, and possibly other versions before 2.1.21, allows remote unauthenticated attackers to cause a denial of service (segmentation fault) via malformed

How urgent is CVE-2006-1721?

Priority 30/100. No elevated risk signals yet.

Related CVEs

CVE-2026-56968 LOW 3.7 UPGRADE MITIGATE GNU SASL before 2.2.4 lacks sanitization of a short challenge in _gsasl_ntlm_client_step in the NTLM client, w
CVE-2022-48195 CRITICAL 9.8 DOWNGRADE An issue was discovered in Mellium mellium.im/sasl before 0.3.1
CVE-2005-0373 HIGH 7.5 DOWNGRADE DOWNGRADE Buffer overflow in digestmd5.c CVS release 1.170 (also referred to as digestmda5.c), as used in the DIGEST-MD5
CVE-2004-0884 HIGH 7.2 DOWNGRADE MITIGATE The (1) libsasl and (2) libsasl2 libraries in Cyrus-SASL 2.1.18 and earlier trust the SASL_PATH environment va
CVE-2002-2043 HIGH 7.5 DOWNGRADE SQL injection vulnerability in the LDAP and MySQL authentication patch for Cyrus SASL 1.5.24 and 1.5.27 allows

References

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