What’s Vulnerable › Vulnerabilities

CVE-2019-16791: downgrade of effective Strict Transport Security (STS) policy in postfix-mta-sts-resolver

• Severity: medium (CVSS 5.9 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.9% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2020-01-22 · updated 2026-06-17
• Weakness: CWE-757

Description

In postfix-mta-sts-resolver before 0.5.1, All users can receive incorrect response from daemon under rare conditions, rendering downgrade of effective STS policy.

Affected products

• Snawoot postfix-mta-sts-resolver: before 0.5.1 — fixed in 0.5.1

How to fix

Upgrade to a fixed version: Snawoot postfix-mta-sts-resolver 0.5.1. Check the vendor advisory for mitigations.

References

• https://gist.github.com/Snawoot/b9da85d6b26dea5460673b29df1adc6b
• https://github.com/Snawoot/postfix-mta-sts-resolver/security/advisories/GHSA-h92m-42h4-82f6
• https://gist.github.com/Snawoot/b9da85d6b26dea5460673b29df1adc6b
• https://github.com/Snawoot/postfix-mta-sts-resolver/security/advisories/GHSA-h92m-42h4-82f6

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