The Mozilla Maintenance Service "helper.exe" application creates a temporary directory writable by non-privileged users.

published 2018-06-11 8 y ago modified 2026-06-17 4 mo ago also EUVD-2017-16736

cvss: 5.5; version 3.0, NVD
cisa kev: Not listed; not in CISA's catalog
epss: 0.3%; EPSS 0.3% chance of exploitation in 30 days, percentile 23%
public exploits: 0; none known

The Mozilla Maintenance Service "helper.exe" application creates a temporary directory writable by non-privileged users. When this is combined with creation of a junction (a form of symbolic link), protected files in the target directory of the junction can be deleted by the Mozilla Maintenance Service, which has privileged access. Note: This attack requires local system access and only affects Windows. Other operating systems are not affected. This vulnerability affects Firefox ESR < 52.2 and Firefox < 54.

Patch / fix

fixed in 2 distros 1

Mozilla Firefox ESR 52.2
Mozilla Firefox 54

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

0.30% chance of exploitation in the next 30 days, higher than 23% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by	version	score	vector
NVD	3.0	5.5	CVSS:3.0/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N
NVD	2.0	3.6	AV:L/AC:L/Au:N/C:N/I:P/A:P

Affected products

Mozilla Firefox ESR
Mozilla Firefox

Classification

Weakness

CWE-276 Incorrect Default Permissions

References

bugzilla.mozilla.org /show_bug.cgi?id=1215648
issue-tracking, vendor-advisory
mozilla.org /security/advisories/mfsa2017-15/
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
sourceforge.net /p/nsis/bugs/1125/
issue-tracking, third-party-advisory

Sources

CVE List CVE-2017-7761
NVD CVE-2017-7761

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