What is CVE-2016-5271?

CVE-2016-5271 is a medium-severity vulnerability in Mozilla Firefox, classified under Out-of-bounds Read. CVSS score: 6.5/10. Published 2016-09-22.

How severe is CVE-2016-5271?

Medium severity. CVSS v3 base score is 6.5 out of 10.

Out-of-bounds Read in Mozilla Firefox

CVE-2016-5271

The PropertyProvider::GetSpacingInternal function in Mozilla Firefox before 49.0 allows remote attackers to cause a denial of service (out-of-bounds read and application crash) via text runs in conjunction with a "display: contents" Cascading Style Sheets (CSS) property.

Vulnerability class: Buffer Overflow

Published 2016-09-22 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 6.5 (Medium). Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H.

EPSS exploit prediction

EPSS: 0.014 (71.8th percentile), scored 2026-10-02.

Low probability of exploitation in the next 30 days, but still tracked. 72nd percentile — 71.8% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.014 · newest: 0.014 · change: 0.000

Affected products

Mozilla Firefox

Weakness classification (CWE)

CWE-125 — Out-of-bounds Read

References

www.mozilla.org/security/announce/2016/mfsa2016-85.html (Vendor Advisory)
www.securityfocus.com/bid/93052 (vdb-entry)
security.gentoo.org/glsa/201701-15 (vendor-advisory)
bugzilla.mozilla.org/show_bug.cgi (Issue Tracking)
www.securitytracker.com/id/1036852 (vdb-entry)

Frequently asked questions

What is CVE-2016-5271?: CVE-2016-5271 is a medium-severity vulnerability in Mozilla Firefox, classified under Out-of-bounds Read. CVSS score: 6.5/10. Published 2016-09-22.
How severe is CVE-2016-5271?: Medium severity. CVSS v3 base score is 6.5 out of 10.