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CVE-2015-2721

15
FAUCET Score

CVE-2015-2721 is a vulnerability in Mozilla Network Security Services (NSS) that affects various Mozilla products like Firefox and Thunderbird, as well as other products using NSS. It allows man-in-the-middle attackers to bypass cryptographic protections, specifically by removing forward secrecy through blocking ServerKeyExchange messages, known as a "SMACK SKIP-TLS" issue. With a CVSS score of 4.3, this vulnerability has a medium attack complexity and could lead to partial integrity compromise without requiring authentication. There is no evidence of active exploitation, publicly available exploit code (Metasploit, Nuclei, ExploitDB), or significant community discussion or media coverage.

Impacted Technologies

VendorProductVersion(s)CPE
12.0CPE matchmatch criteria
cpe:2.3:a:novell:suse_linux_enterprise_software_development_kit:12.0:*:*:*:*:*:*:*
12.04CPE matchmatch criteria
cpe:2.3:o:canonical:ubuntu_linux:12.04:*:*:*:lts:*:*:*
14.04CPE matchmatch criteria
cpe:2.3:o:canonical:ubuntu_linux:14.04:*:*:*:lts:*:*:*
14.10CPE matchmatch criteria
cpe:2.3:o:canonical:ubuntu_linux:14.10:*:*:*:*:*:*:*
15.04CPE matchmatch criteria
cpe:2.3:o:canonical:ubuntu_linux:15.04:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 2.0

4.3MEDIUM

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

Confidentiality Impact
NONE
Integrity Impact
PARTIAL
Availability Impact
NONE
Access Vector
NETWORK
Access Complexity
MEDIUM
Authentication
NONE
Exploitability Score
8.6
Impact Score
2.9
CvssVersion
2.0

Exploit Intelligence

EPSS Score
3.28%
Probability of exploitation in next 30 days
EPSS Percentile
87.1%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.0328 is in the 81st percentile among its peer group of 19,958 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, 0.0 Bluesky, 0.0 Mastodon, and 0.2 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 (6)

redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 5Fixed in: nss-0:3.19.1-1.el5_11
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 6Fixed in: nss-0:3.19.1-3.el6_6
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 6Fixed in: nss-util-0:3.19.1-1.el6_6
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 7Fixed in: nss-0:3.19.1-3.ael7b_1
View patch
redhatpatch availablevia redhat_api
Product: Red Hat Enterprise Linux 7Fixed in: nss-util-0:3.19.1-1.ael7b_1
View patch
mozillavendor investigatingvia nvd_reference
View patch

Vendor Advisories (1)

redhatCVE-2015-2721Moderate

NSS: incorrectly permited skipping of ServerKeyExchange (MFSA 2015-71)

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-2015-1185.html
rhn.redhat.com / errata/RHSA-2015-1664.html
bugzilla.mozilla.org / show_bug.cgi
ExploitIssue TrackingVDB EntryVendor Advisory
developer.mozilla.org / en-US/docs/Mozilla/Projects/NSS/NSS_3.19_release_notes
Release Notes
security.gentoo.org / glsa/201512-10
security.gentoo.org / glsa/201701-46
smacktls.com
Technical Description
debian.org / security/2015/dsa-3324
Third Party Advisory
debian.org / security/2015/dsa-3336
Third Party Advisory
mozilla.org / security/announce/2015/mfsa2015-71.html
Vendor Advisory
oracle.com / technetwork/security-advisory/cpuapr2016v3-2985753.html
Third Party Advisory
oracle.com / technetwork/security-advisory/cpujul2016-2881720.html
Third Party Advisory
oracle.com / technetwork/topics/security/bulletinapr2016-2952098.html
Third Party Advisory
oracle.com / technetwork/topics/security/bulletinoct2015-2511968.html
Third Party Advisory
oracle.com / technetwork/topics/security/ovmbulletinjul2016-3090546.html
Third Party Advisory
securityfocus.com / bid/75541
securityfocus.com / bid/83398
securityfocus.com / bid/91787
Third Party Advisory
securitytracker.com / id/1032783
securitytracker.com / id/1032784
ubuntu.com / usn/USN-2656-1
ubuntu.com / usn/USN-2656-2
ubuntu.com / usn/USN-2672-1
ubuntu.com / usn/USN-2673-1
Third Party Advisory