CVE-2017-7789

Severity: medium (CVSS 5.3 v3.0)
Exploited in the wild: not listed in CISA KEV
EPSS: 1.7% probability of exploitation in the next 30 days
Public exploit or detection template: yes
Published: 2018-06-11 · updated 2026-06-17

Description

If a server sends two Strict-Transport-Security (STS) headers for a single connection, they will be rejected as invalid and HTTP Strict Transport Security (HSTS) will not be enabled for the connection. This vulnerability affects Firefox < 55.

Affected products

Mozilla Firefox: before 55.0 — fixed in 55.0

How to fix

Upgrade to a fixed version: Mozilla Firefox 55.0. Check the vendor advisory for mitigations.

References

http://www.securityfocus.com/bid/100374
http://www.securitytracker.com/id/1039124
https://bugzilla.mozilla.org/show_bug.cgi?id=1074642
https://www.mozilla.org/security/advisories/mfsa2017-18/
http://www.securityfocus.com/bid/100374
http://www.securitytracker.com/id/1039124
https://bugzilla.mozilla.org/show_bug.cgi?id=1074642
https://www.mozilla.org/security/advisories/mfsa2017-18/

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