Vulnerability identifier: #VU32328

Vulnerability risk: Medium

CVSSv3.1: 5.7 [CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N/E:U/RL:O/RC:C]

CVE-ID: CVE-2016-1938

CWE-ID: CWE-310

Exploitation vector: Network

Exploit availability: No

Vulnerable software:
Mozilla NSS
Universal components / Libraries / Libraries used by multiple products

Vendor: Mozilla

Description

The vulnerability allows a remote non-authenticated attacker to read and manipulate data.

The s_mp_div function in lib/freebl/mpi/mpi.c in Mozilla Network Security Services (NSS) before 3.21, as used in Mozilla Firefox before 44.0, improperly divides numbers, which might make it easier for remote attackers to defeat cryptographic protection mechanisms by leveraging use of the (1) mp_div or (2) mp_exptmod function.

Mitigation
Install update from vendor's website.

Vulnerable software versions

Mozilla NSS: 3.13.4 - 3.52.1

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External links
http://lists.opensuse.org/opensuse-security-announce/2016-02/msg00001.html
http://lists.opensuse.org/opensuse-security-announce/2016-02/msg00002.html
http://lists.opensuse.org/opensuse-security-announce/2016-02/msg00010.html
http://www.debian.org/security/2016/dsa-3688
http://www.mozilla.org/security/announce/2016/mfsa2016-07.html
http://www.oracle.com/technetwork/security-advisory/cpujul2016-2881720.html
http://www.securityfocus.com/bid/81955
http://www.securityfocus.com/bid/91787
http://www.securitytracker.com/id/1034825
http://www.ubuntu.com/usn/USN-2880-1
http://www.ubuntu.com/usn/USN-2880-2
http://www.ubuntu.com/usn/USN-2903-1
http://www.ubuntu.com/usn/USN-2903-2
http://www.ubuntu.com/usn/USN-2973-1
http://blog.fuzzing-project.org/37-Mozilla-NSS-Wrong-calculation-results-in-mp_div-and-mp_exptmod.html
http://bugzilla.mozilla.org/show_bug.cgi?id=1190248
http://bugzilla.mozilla.org/show_bug.cgi?id=1194947
http://developer.mozilla.org/en-US/docs/Mozilla/Projects/NSS/NSS_3.21_release_notes
http://github.com/hannob/bignum-fuzz/blob/master/CVE-2016-1938-nss-mp_div.c
http://github.com/hannob/bignum-fuzz/blob/master/CVE-2016-1938-nss-mp_exptmod.c
http://hg.mozilla.org/projects/nss/diff/a555bf0fc23a/lib/freebl/mpi/mpi.c
http://security.gentoo.org/glsa/201605-06
http://security.gentoo.org/glsa/201701-46

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Q & A

Can this vulnerability be exploited remotely?

Yes. This vulnerability can be exploited by a remote non-authenticated attacker via the Internet.

Is there known malware, which exploits this vulnerability?

No. We are not aware of malware exploiting this vulnerability.