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CVE-2016-9063

31
FAUCET Score

CVE-2016-9063 is a critical integer overflow vulnerability in the Expat XML parsing library, affecting Firefox versions prior to 50, as well as various Debian and Python products utilizing this library. With a CVSS score of 9.8, it allows for unauthenticated, low-complexity remote attacks that can lead to complete compromise of confidentiality, integrity, and availability. While the EPSS score is low and it's not on the KEV catalog, there is no public exploit code available (Metasploit, Nuclei, ExploitDB), and community discussion and media coverage are minimal, suggesting limited active exploitation.

Impacted Technologies

VendorProductVersion(s)CPE
< 50CPE matchmatch criteria
cpe:2.3:a:mozilla:firefox:*:*:*:*:*:*:*:*
8.0CPE matchmatch criteria
cpe:2.3:o:debian:debian_linux:8.0:*:*:*:*:*:*:*
9.0CPE matchmatch criteria
cpe:2.3:o:debian:debian_linux:9.0:*:*:*:*:*:*:*
10.0CPE matchmatch criteria
cpe:2.3:o:debian:debian_linux:10.0:*:*:*:*:*:*:*
>= 2.7.0, < 2.7.15CPE matchmatch criteria
cpe:2.3:a:python:python:*:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

9.8CRITICAL

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
HIGH
Integrity Impact
HIGH
Availability Impact
HIGH
Exploitability Score
3.9
Impact Score
5.9
CvssVersion
3.1

Exploit Intelligence

EPSS Score
5.74%
Probability of exploitation in next 30 days
EPSS Percentile
92.3%
Percentile rank of EPSS score among Peer Group
As of 2026-07-26
Model: v2026.06.15
This CVE's current EPSS score of 0.0574 is in the 87th percentile among its peer group of 36,835 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.1 Reddit, 0.3 Bluesky, 0.3 Mastodon, and 2.4 GitHub mentions.

Media Mentions

The average CVE in this peer group has 0.3 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Vendor Patches (8)

mozillavendor investigatingvia nvd_reference
View patch
redhatend of lifevia redhat_api
Product: Red Hat Enterprise Linux 5Fixed in: expat
redhatend of lifevia redhat_api
Product: Red Hat Enterprise Linux 6Fixed in: compat-expat1
redhatend of lifevia redhat_api
Product: Red Hat Enterprise Linux 6Fixed in: expat
redhatend of lifevia redhat_api
Product: Red Hat Enterprise Linux 7Fixed in: expat
redhatend of lifevia redhat_api
Product: Red Hat Enterprise Virtualization 3Fixed in: mingw-virt-viewer
redhatend of lifevia redhat_api
Product: Red Hat JBoss Enterprise Application Platform 6Fixed in: httpd
redhatend of lifevia redhat_api
Product: Red Hat JBoss Enterprise Web Server 2Fixed in: expat

Vendor Advisories (1)

redhatCVE-2016-9063Low

firefox: Possible integer overflow to fix inside XML_Parse in Expat

Nov 15, 2016

References

bugzilla.mozilla.org / show_bug.cgi
Issue TrackingVendor Advisory
debian.org / security/2017/dsa-3898
Third Party Advisory
mozilla.org / security/advisories/mfsa2016-89
Vendor Advisory
securityfocus.com / bid/94337
Third Party AdvisoryVDB Entry
securitytracker.com / id/1037298
Third Party AdvisoryVDB Entry
securitytracker.com / id/1039427
Third Party AdvisoryVDB Entry