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CVE-2015-4520

18
FAUCET Score

CVE-2015-4520 is a vulnerability in Mozilla Firefox versions before 41.0 and Firefox ESR 38.x before 38.3, allowing remote attackers to bypass Cross-Origin Resource Sharing (CORS) preflight protection. This medium-severity vulnerability (CVSS 6.4) has a low attack complexity and could lead to unauthorized information disclosure and modification. There is no evidence of active exploitation, publicly available exploit code, or significant community discussion surrounding this CVE.

Impacted Technologies

VendorProductVersion(s)CPE
38.0CPE matchmatch criteria
cpe:2.3:a:mozilla:firefox:38.0:*:*:*:*:*:*:*
38.0.1CPE matchmatch criteria
cpe:2.3:a:mozilla:firefox:38.0.1:*:*:*:*:*:*:*
38.0.5CPE matchmatch criteria
cpe:2.3:a:mozilla:firefox:38.0.5:*:*:*:*:*:*:*
38.1.0CPE matchmatch criteria
cpe:2.3:a:mozilla:firefox:38.1.0:*:*:*:*:*:*:*
38.1.1CPE matchmatch criteria
cpe:2.3:a:mozilla:firefox:38.1.1:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 2.0

6.4MEDIUM

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

Confidentiality Impact
PARTIAL
Integrity Impact
PARTIAL
Availability Impact
NONE
Access Vector
NETWORK
Access Complexity
LOW
Authentication
NONE
Exploitability Score
10.0
Impact Score
4.9
CvssVersion
2.0

Exploit Intelligence

EPSS Score
3.09%
Probability of exploitation in next 30 days
EPSS Percentile
86.4%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.0309 is in the 81st percentile among its peer group of 23,723 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, 0.0 Mastodon, and 0.4 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

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

Remediation

Patch Available

Vendor Patches (7)

redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 6Fixed in: firefox-0:38.3.0-2.el6_7
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 5Fixed in: firefox-0:38.3.0-2.el5_11
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 5Fixed in: thunderbird-0:38.3.0-1.el5_11
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 7Fixed in: thunderbird-0:38.3.0-1.el7_1
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 6Fixed in: thunderbird-0:38.3.0-1.el6_7
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 7Fixed in: firefox-0:38.3.0-2.ael7b_1
View patch
mozillavendor investigatingvia nvd_reference
View patch

Vendor Advisories (1)

redhatCVE-2015-4520Important

Mozilla: Errors in the handling of CORS preflight request headers (MFSA 2015-111)

Sep 22, 2015

References

lists.opensuse.org / opensuse-security-announce/2015-10/msg00000.html
lists.opensuse.org / opensuse-security-announce/2015-10/msg00003.html
lists.opensuse.org / opensuse-security-announce/2015-10/msg00004.html
lists.opensuse.org / opensuse-security-announce/2015-10/msg00005.html
lists.opensuse.org / opensuse-security-announce/2015-10/msg00007.html
lists.opensuse.org / opensuse-security-announce/2015-11/msg00025.html
rhn.redhat.com / errata/RHSA-2015-1834.html
rhn.redhat.com / errata/RHSA-2015-1852.html
bugzilla.mozilla.org / show_bug.cgi
bugzilla.mozilla.org / show_bug.cgi
debian.org / security/2015/dsa-3365
mozilla.org / security/announce/2015/mfsa2015-111.html
Vendor Advisory
oracle.com / technetwork/topics/security/bulletinapr2016-2952098.html
oracle.com / technetwork/topics/security/linuxbulletinoct2015-2719645.html
securityfocus.com / bid/76816
securitytracker.com / id/1033640
ubuntu.com / usn/USN-2743-1
ubuntu.com / usn/USN-2743-2
ubuntu.com / usn/USN-2743-3
ubuntu.com / usn/USN-2743-4
ubuntu.com / usn/USN-2754-1