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CVE-2017-7789

17
FAUCET Score

CVE-2017-7789 describes a vulnerability in Firefox versions prior to 55 where sending two Strict-Transport-Security (STS) headers for a single connection causes them to be rejected, preventing HTTP Strict Transport Security (HSTS) from being enabled. This medium-severity vulnerability (CVSS 5.3) has a network attack vector and low attack complexity, potentially leading to a loss of integrity (I:L) by bypassing HSTS protections. There is no evidence of active exploitation, publicly available exploit code, or significant community discussion surrounding this CVE.

Impacted Technologies

VendorProductVersion(s)CPE
< 55.0CPE matchmatch criteria
cpe:2.3:a:mozilla:firefox:*:*:*:*:*:*:*:*
< 55CPE match
cpe:2.3:a:mozilla:firefox:*:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.0

5.3MEDIUM

CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
NONE
Integrity Impact
LOW
Availability Impact
NONE
Exploitability Score
3.9
Impact Score
1.4
CvssVersion
3.0

Exploit Intelligence

EPSS Score
1.78%
Probability of exploitation in next 30 days
EPSS Percentile
76.0%
Percentile rank of EPSS score among Peer Group
As of 2026-07-26
Model: v2026.06.15
This CVE's current EPSS score of 0.0178 is in the 63rd percentile among its peer group of 23,701 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.0 Reddit, 0.1 Bluesky, 0.0 Mastodon, and 0.4 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.0 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Vendor Patches (1)

mozillavendor investigatingvia nvd_reference
View patch

Vendor Advisories (1)

redhatCVE-2017-7789Low

Mozilla: Failure to enable HSTS when two STS headers are sent for a connection (MFSA 2017-18)

Aug 8, 2017

References

bugzilla.mozilla.org / show_bug.cgi
ExploitIssue TrackingVendor Advisory
mozilla.org / security/advisories/mfsa2017-18
Vendor Advisory
securityfocus.com / bid/100374
Third Party AdvisoryVDB Entry
securitytracker.com / id/1039124
Third Party AdvisoryVDB Entry