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CVE-2015-2733

27
FAUCET Score

CVE-2015-2733 is a critical use-after-free vulnerability in the CanonicalizeXPCOMParticipant function affecting Mozilla Firefox before version 39.0 and Firefox ESR 31.x before 31.8 and 38.x before 38.1. This flaw allows remote attackers to execute arbitrary code by manipulating XMLHttpRequest objects with dedicated workers. With a CVSS score of 10.0, it presents a severe risk due to its network-based attack vector, low attack complexity, and complete compromise of confidentiality, integrity, and availability. While there is no evidence of active exploitation or public exploit code (Metasploit, Nuclei, ExploitDB), the vulnerability has received some community attention and media coverage, indicating its recognized severity.

Impacted Technologies

VendorProductVersion(s)CPE
<= 38.1.0CPE matchmatch criteria
cpe:2.3:a:mozilla:firefox:*:*:*:*:*:*:*:*
11.3CPE matchmatch criteria
cpe:2.3:o:oracle:solaris:11.3:*:*:*:*:*:*:*
31.0CPE matchmatch criteria
cpe:2.3:a:mozilla:firefox:31.0:*:*:*:*:*:*:*
31.1.0CPE matchmatch criteria
cpe:2.3:a:mozilla:firefox:31.1.0:*:*:*:*:*:*:*
31.1.1CPE matchmatch criteria
cpe:2.3:a:mozilla:firefox:31.1.1:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 2.0

10.0HIGH

AV:N/AC:L/Au:N/C:C/I:C/A:C

Confidentiality Impact
COMPLETE
Integrity Impact
COMPLETE
Availability Impact
COMPLETE
Access Vector
NETWORK
Access Complexity
LOW
Authentication
NONE
Exploitability Score
10.0
Impact Score
10.0
CvssVersion
2.0

Exploit Intelligence

EPSS Score
6.18%
Probability of exploitation in next 30 days
EPSS Percentile
92.7%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.0618 is in the 88th percentile among its peer group of 51,551 CVEs.

Social Chatter

No social media mentions found for this CVE.

The average CVE in this peer group has 0.0 Twitter, 0.0 Reddit, 0.1 Bluesky, 0.1 Mastodon, and 0.4 GitHub mentions.

Media Mentions

The average CVE in this peer group has 0.1 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Patch Available

Vendor Patches (4)

redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 5Fixed in: firefox-0:38.1.0-1.el5_11
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 6Fixed in: firefox-0:38.1.0-1.el6_6
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 7Fixed in: firefox-0:38.1.0-1.ael7b_1
View patch
mozillavendor investigatingvia nvd_reference
View patch

Vendor Advisories (1)

redhatCVE-2015-2733Critical

Mozilla: Use-after-free in workers while using XMLHttpRequest (MFSA 2015-65)

Jul 2, 2015

References

lists.opensuse.org / opensuse-security-announce/2015-07/msg00025.html
lists.opensuse.org / opensuse-security-announce/2015-07/msg00031.html
lists.opensuse.org / opensuse-security-announce/2015-07/msg00033.html
Third Party Advisory
lists.opensuse.org / opensuse-security-announce/2015-07/msg00034.html
Third Party Advisory
lists.opensuse.org / opensuse-security-announce/2015-08/msg00021.html
rhn.redhat.com / errata/RHSA-2015-1207.html
bugzilla.mozilla.org / show_bug.cgi
Issue Tracking
security.gentoo.org / glsa/201512-10
mozilla.org / security/announce/2015/mfsa2015-65.html
Vendor Advisory
oracle.com / technetwork/topics/security/bulletinapr2016-2952098.html
Third Party Advisory
oracle.com / technetwork/topics/security/bulletinoct2015-2511968.html
Third Party Advisory
securityfocus.com / bid/75541
securitytracker.com / id/1032783
securitytracker.com / id/1032784
ubuntu.com / usn/USN-2656-1
ubuntu.com / usn/USN-2656-2