Memory safety bugs were reported in Firefox 51.

published 2018-06-11 8 y ago modified 2026-06-17 4 mo ago also EUVD-2017-14503

cvss: 9.8; version 3.0, NVD
cisa kev: Not listed; not in CISA's catalog
epss: 2.3%; EPSS 2.3% chance of exploitation in 30 days, percentile 83%
public exploits: 0; none known

Memory safety bugs were reported in Firefox 51. Some of these bugs showed evidence of memory corruption and we presume that with enough effort that some of these could be exploited to run arbitrary code. This vulnerability affects Firefox < 52 and Thunderbird < 52.

Patch / fix

fixed in 2 distros 3

Mozilla Firefox 52
Mozilla Thunderbird 52

ubuntu opensuse arch linux

firefox Ubuntu 14.04 LTS 52.0+build2-0ubuntu0.14.04.1
firefox Ubuntu 16.04 LTS 52.0+build2-0ubuntu0.16.04.1

ubuntu advisories UBUNTU-CVE-2017-5399

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

firefox-esr openSUSE Tumbleweed 128.5.1-1.1
MozillaFirefox openSUSE Tumbleweed 92.0-1.2
MozillaThunderbird openSUSE Tumbleweed 91.1.1-1.1
MozillaThunderbird Package Hub 12 52.1.0-30.1

opensuse advisories openSUSE-SU-2024:14572-1 openSUSE-SU-2024:10600-1 openSUSE-SU-2024:10601-1 openSUSE-SU-2017:1268-1

firefox Arch Linux 52.0-1

arch linux advisories AVG-194

Exploit prediction

2.27% chance of exploitation in the next 30 days, higher than 83% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by	version	score	vector
NVD	3.0	9.8	CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
NVD	2.0	10.0	AV:N/AC:L/Au:N/C:C/I:C/A:C

Affected products

Mozilla Firefox
Mozilla Thunderbird

Classification

Weakness

CWE-119 Improper Restriction of Operations within the Bounds of a Memory Buffer

References

mozilla.org /security/advisories/mfsa2017-09/
vendor-advisory
mozilla.org /security/advisories/mfsa2017-05/
vendor-advisory
bugzilla.mozilla.org /buglist.cgi?bug_id=1332569%2C1315248%2C1261335%2C1321038%2C1331771%2C1339566%2C1339591%2C1240893%2C1341905%2C
issue-tracking, permissions-required, third-party-advisory
securitytracker.com /id/1037966
vdb-entry, third-party-advisory
securityfocus.com /bid/96692
vdb-entry, third-party-advisory

Sources

CVE List CVE-2017-5399
NVD CVE-2017-5399

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