The Firefox installer on Windows can be made to load malicious DLL files stored in the same directory as the installer when it is run.

published 2018-06-11 8 y ago modified 2026-06-17 4 mo ago also EUVD-2017-16730

cvss: 7.8; version 3.0, NVD
cisa kev: Not listed; not in CISA's catalog
epss: 1.4%; EPSS 1.4% chance of exploitation in 30 days, percentile 71%
public exploits: 0; none known

The Firefox installer on Windows can be made to load malicious DLL files stored in the same directory as the installer when it is run. This allows privileged execution if the installer is run with elevated privileges. Note: This attack only affects Windows operating systems. Other operating systems are unaffected. This vulnerability affects Firefox < 54, Firefox ESR < 52.2, and Thunderbird < 52.2.

Patch / fix

fixed in 3 distros 1

Mozilla Firefox 54
Mozilla Firefox ESR 52.2
Mozilla Thunderbird 52.2

mozilla-nss SLES for SAP 11 SP4, SLES 11 SP4, SLES 11 SP3-TERADATA +3 more 3.29.5-47.3.2
firefox-gcc5 SLES for SAP 11 SP4, SLES 11 SP4, SLES 11 SP3-TERADATA +2 more 5.3.1+r233831-7.1
MozillaFirefox SLES for SAP 11 SP4, SLES 11 SP4, SLES 11 SP3-TERADATA +3 more 52.2.0esr-72.5.2
firefox-libffi-gcc5 SLES for SAP 11 SP4, SLES 11 SP4, SLES 11 SP3-TERADATA +2 more 5.3.1+r233831-7.1
MozillaFirefox-branding-SLED SLES for SAP 11 SP4, SLES 11 SP4, SLES 11 SP3-TERADATA +2 more 52-24.3.44
MozillaFirefox-branding-SLE SLES for SAP 12 SP2, SLES for SAP 12 SP1, SLES for SAP 12 +6 more 52-31.1
MozillaFirefox SLES for SAP 12 SP2, SLES for SAP 12 SP1, SLES for SAP 12 +7 more 52.2.0esr-108.3

suse advisories SUSE-SU-2017:2235-1 SUSE-SU-2017:1669-1

Exploit prediction

1.36% chance of exploitation in the next 30 days, higher than 71% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by	version	score	vector
NVD	3.0	7.8	CVSS:3.0/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
NVD	2.0	6.8	AV:N/AC:M/Au:N/C:P/I:P/A:P

Affected products

Mozilla Firefox
Mozilla Firefox ESR
Mozilla Thunderbird

Classification

Weakness

CWE-426 Untrusted Search Path

References

mozilla.org /security/advisories/mfsa2017-15/
vendor-advisory
bugzilla.mozilla.org /show_bug.cgi?id=1361326
issue-tracking, vendor-advisory
mozilla.org /security/advisories/mfsa2017-17/
vendor-advisory
mozilla.org /security/advisories/mfsa2017-16/
vendor-advisory
securityfocus.com /bid/99057
vdb-entry, third-party-advisory
securitytracker.com /id/1038689
vdb-entry, third-party-advisory

Sources

CVE List CVE-2017-7755
NVD CVE-2017-7755

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

Summary