CVE-2019-16791
downgrade of effective Strict Transport Security (STS) policy in postfix-mta-sts-resolver
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.
Attack profile
How easy it is to exploit
- Attack vector
- Local
- Complexity
- High
- Privileges needed
- High
- User interaction
- Required
What an attacker can affect
- Confidentiality
- High
- Integrity
- High
- Availability
- None
Exploit likelihood
What each source reports
CVE List Score used
downgrade of effective Strict Transport Security (STS) policy in postfix-mta-sts-resolver
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.
- Record
CVE-2019-16791- CVSS 3.1
- 6.9 Medium
CVSS:3.1/AV:L/AC:H/PR:H/UI:R/S:C/C:H/I:H/A:N - Weakness
- CWE-757
- Updated
- 2026-11-02
EUVDEUVD-2020-0149
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.
- Record
EUVD-2020-0149- CVSS 3.1
- 6.9 Medium
CVSS:3.1/AV:L/AC:H/PR:H/UI:R/S:C/C:H/I:H/A:N - Updated
- 2026-11-03
GitHub AdvisoriesGHSA-h92m-42h4-82f6
postfix-mta-sts-resolver Algorithm Downgrade vulnerability
Incorrect query parsing
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.
Patches
Problem has been patched in version 0.5.1
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
- Record
GHSA-h92m-42h4-82f6- CVSS 4.0
- 8.7 High
CVSS:4.0/AV:N/AC:L/AT:P/PR:H/UI:N/VC:H/VI:H/VA:N/SC:H/SI:H/SA:N - CVSS 3.1
- 6.9 Medium
CVSS:3.1/AV:L/AC:H/PR:H/UI:R/S:C/C:H/I:H/A:N - Weakness
- CWE-757
- Updated
- 2026-11-02
NVD
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.
- Record
CVE-2019-16791- CVSS 3.1
- 6.9 Medium
CVSS:3.1/AV:L/AC:H/PR:H/UI:R/S:C/C:H/I:H/A:N - CVSS 3.1
- 5.9 Medium
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H - CVSS 2.0
- 4.3 Medium
AV:N/AC:M/Au:N/C:N/I:N/A:P - Weakness
- CWE-757
- Updated
- 2026-11-02
OSV
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.
- Record
CVE-2019-16791- CVSS 3.1
- 5.9 Medium
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H - Updated
- 2026-11-02
OSVGHSA-h92m-42h4-82f6
postfix-mta-sts-resolver Algorithm Downgrade vulnerability
Incorrect query parsing
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.
Patches
Problem has been patched in version 0.5.1
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
- Record
GHSA-h92m-42h4-82f6- CVSS 4.0
- 8.7 High
CVSS:4.0/AV:N/AC:L/AT:P/PR:H/UI:N/VC:H/VI:H/VA:N/SC:H/SI:H/SA:N - CVSS 3.1
- 6.9 Medium
CVSS:3.1/AV:L/AC:H/PR:H/UI:R/S:C/C:H/I:H/A:N - Weakness
- CWE-757
- Updated
- 2026-11-02
OSVUBUNTU-CVE-2019-16791
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.
- Record
UBUNTU-CVE-2019-16791- CVSS 3.1
- 6.9 Medium
CVSS:3.1/AV:L/AC:H/PR:H/UI:R/S:C/C:H/I:H/A:N - CVSS 3.1
- 5.9 Medium
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H - Updated
- 2026-11-02
OSVPYSEC-2020-174 No score
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.
- Record
PYSEC-2020-174- Updated
- 2026-11-02
Affected products
Affected packages
| Package | Affected | Fixed |
|---|---|---|
postfix-mta-sts-resolverPyPI |
before 0.5.1 | 0.5.1 |
postfix-mta-sts-resolverPyPI |
before 0.5.1, plus listed versions 0.1.10.1.20.1.30.1.40.1.5 Show 17 moreShow less0.2.00.2.10.2.20.2.30.2.40.2.50.2.70.2.80.2.90.3.00.4.00.4.10.4.20.4.30.4.40.4.50.5.0 |
0.5.1 |
postfix-mta-sts-resolverUbuntu:20.04:LTS |
All versions, plus listed versions 0.6.0-10.7.0-10.7.3-10.7.5-1 |
None known |
postfix-mta-sts-resolverUbuntu:22.04:LTS |
All versions, plus listed versions 1.0.0-41.1.2-1 |
None known |
postfix-mta-sts-resolverUbuntu:24.04:LTS |
All versions, plus listed versions 1.1.2-1.11.1.2-1.1ubuntu0.1 |
None known |
postfix-mta-sts-resolverUbuntu:25.10 |
All versions, plus listed versions 1.5.0-1 |
None known |
postfix-mta-sts-resolverUbuntu:26.10 |
All versions, plus listed versions 1.5.0-1build11.5.1-1 |
None known |
postfix-mta-sts-resolverUbuntu:26.04:LTS |
All versions, plus listed versions 1.5.0-11.5.0-1build1 |
None known |
History
| Recorded | Changed | Sources |
|---|---|---|
| aliases | EUVD | |
| first indexed | CVE List, GitHub Advisories, NVD, OSV |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2019-16791 is a medium vulnerability (CVSS 6.9) in Postfix-mta-sts-resolver Project Postfix-mta-sts-resolver, published July 5, 2019. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.86%, the 58th percentile. Fixed in postfix-mta-sts-resolver 0.5.1.
References
github.com/Snawoot/postfix-mta-sts-resolver/security/advisories/GHSA-h92m-42h4-82f6
gist.github.com/Snawoot/b9da85d6b26dea5460673b29df1adc6b
nvd.nist.gov/vuln/detail/CVE-2019-16791
ubuntu.com/security/CVE-2019-16791
cve.org/CVERecord?id=CVE-2019-16791