What is CVE-2019-16791?

CVE-2019-16791 is a high-severity security vulnerability in postfix-mta-sts-resolver (pip), affecting versions < 0.5.1. It is fixed in 0.5.1.

How severe is CVE-2019-16791?

CVE-2019-16791 has a CVSS score of 6.9 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.

Which versions of postfix-mta-sts-resolver are affected by CVE-2019-16791?

postfix-mta-sts-resolver (pip) versions < 0.5.1 is affected.

Is there a fix for CVE-2019-16791?

Yes. CVE-2019-16791 is fixed in 0.5.1. Upgrade to this version or later.

Is CVE-2019-16791 exploitable, and should I be worried?

Whether CVE-2019-16791 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk.

What actually determines whether CVE-2019-16791 is exploitable, and how bad it is?

Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.

How do I fix CVE-2019-16791?

Upgrade postfix-mta-sts-resolver to 0.5.1 or later.

CVE-2019-16791 in postfix-mta-sts-resolver

Q: How severe is CVE-2019-16791?

CVE-2019-16791 has a CVSS score of 6.9 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.

Q: Which versions of postfix-mta-sts-resolver are affected by CVE-2019-16791?

postfix-mta-sts-resolver (pip) versions < 0.5.1 is affected.

Q: Is there a fix for CVE-2019-16791?

Yes. CVE-2019-16791 is fixed in 0.5.1. Upgrade to this version or later.

Q: Is CVE-2019-16791 exploitable, and should I be worried?

Whether CVE-2019-16791 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk.

Q: What actually determines whether CVE-2019-16791 is exploitable, and how bad it is?

Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.

Q: How do I fix CVE-2019-16791?

Upgrade postfix-mta-sts-resolver to 0.5.1 or later.

Summary

postfix-mta-sts-resolver Algorithm Downgrade vulnerability

Incorrect query parsing

Workarounds

Users may remediate this vulnerability without upgrading by applying these patches to older suppoorted versions.

For more information

If you have any questions or comments about this advisory:

Open an issue in postfix-mta-sts-resolver repo
Email me at vladislav at vm-0 dot com

Impact

All users of versions prior to 0.5.1 can receive incorrect response from daemon under rare conditions, rendering downgrade of effective STS policy.

CVE-2019-16791 has a CVSS score of 6.9 (High). The vector is requires local access, high privileges required, and user interaction required. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (0.5.1); upgrading removes the vulnerable code path.

Affected versions

postfix-mta-sts-resolver (< 0.5.1)

Security releases

postfix-mta-sts-resolver → 0.5.1 (pip)

Kodem intelligence

Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.

Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.

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Remediation advice

Problem has been patched in version 0.5.1

Frequently Asked Questions

What is CVE-2019-16791? CVE-2019-16791 is a high-severity security vulnerability in postfix-mta-sts-resolver (pip), affecting versions < 0.5.1. It is fixed in 0.5.1.
How severe is CVE-2019-16791? CVE-2019-16791 has a CVSS score of 6.9 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
Which versions of postfix-mta-sts-resolver are affected by CVE-2019-16791? postfix-mta-sts-resolver (pip) versions < 0.5.1 is affected.
Is there a fix for CVE-2019-16791? Yes. CVE-2019-16791 is fixed in 0.5.1. Upgrade to this version or later.
Is CVE-2019-16791 exploitable, and should I be worried? Whether CVE-2019-16791 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
What actually determines whether CVE-2019-16791 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
How do I fix CVE-2019-16791? Upgrade postfix-mta-sts-resolver to 0.5.1 or later.