CVE-2016-1938

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.

Published: 2016-01-31 Last update: 2026-05-06 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2016-1938 is rated Moderate Risk (53.5/100): CVSS Medium severity, with medium exploitation likelihood (EPSS 1.05%). Review affected assets and schedule remediation.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2016-1938

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-03-02 0.59% 1.05% +0.46%
2 2026-01-06 1.06% 0.59% -0.47%
3 2025-12-07 — 1.06% —

Full EPSS history (11 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2016-1938

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
6.5 3.0 MEDIUM
CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:L)
Some sensitive info could get out, but not a total data dump.
Integrity (I:L)
Attackers could change some data, but it’s limited—not everything goes.
Availability (A:N)
Service keeps running; no real outage angle.
 3.9 2.5 [email protected]
6.4 2.0 MEDIUM
AV:N/AC:L/Au:N/C:P/I:P/A:N Click to expand
Access vector (AV:N)
Can be exploited remotely over network reachability.
Access complexity (AC:L)
Exploitation conditions are straightforward and predictable.
Authentication (AU:N)
No authentication is required.
Confidentiality impact (C:P)
Partial confidentiality impact.
Integrity impact (I:P)
Partial integrity impact.
Availability impact (A:N)
No availability impact.
 10.0 4.9 [email protected]

Weakness enumeration for CVE-2016-1938

OS Trackers for CVE-2016-1938

vendor priority summary link
debian not yet assigned CVE-2016-1938 not yet assigned priority: Debian including 1 source packages (nss), 5 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 5. https://security-tracker.debian.org/tracker/CVE-2016-1938
gentoo normal CVE-2016-1938: 2 GLSA(s) (201605-06, 201701-46), 6 atom(s) (dev-libs/nspr, dev-libs/nss, mail-client/thunderbird, mail-client/thunderbird-bin, www-client/firefox, www-client/firefox-bin); latest impact normal. https://bugs.gentoo.org/buglist.cgi?quicksearch=CVE-2016-1938
redhat low — https://access.redhat.com/security/cve/CVE-2016-1938
suse medium CVE-2016-1938 severity moderate: SUSE including 158 source package names (MozillaFirefox-102.11.0-150200.152.87.1, MozillaFirefox-115.10.0-150200.152.134.1, …), 448 product×package rows across 67 product lines (Image SLES12-SP5-Azure-BYOS, Image SLES12-SP5-Azure-Basic-On-Demand, … (67 product lines)): Fixed 448. https://www.suse.com/security/cve/CVE-2016-1938/
ubuntu medium CVE-2016-1938 medium priority: Ubuntu including 3 source packages (firefox, nss, thunderbird), 24 status rows across 8 suites (precise, trusty, upstream, vivid, wily, xenial, yakkety, zesty): released 19, not-affected 3, ignored 2. https://ubuntu.com/security/CVE-2016-1938

Affected software / configurations for CVE-2016-1938

Vendor Product Version Raw CPE
opensuse leap 42.1 cpe:2.3:o:opensuse:leap:42.1:*:*:*:*:*:*:*
opensuse opensuse 13.1 cpe:2.3:o:opensuse:opensuse:13.1:*:*:*:*:*:*:*
opensuse opensuse 13.2 cpe:2.3:o:opensuse:opensuse:13.2:*:*:*:*:*:*:*
mozilla nss <= 3.20.1 cpe:2.3:a:mozilla:nss:*:*:*:*:*:*:*:*
mozilla firefox <= 43.0.4 cpe:2.3:a:mozilla:firefox:*:*:*:*:*:*:*:*

References for CVE-2016-1938

URL Tags
http://lists.opensuse.org/opensuse-security-announce/2016-02/msg00001.html Third Party Advisory
http://lists.opensuse.org/opensuse-security-announce/2016-02/msg00002.html Third Party Advisory
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 Vendor Advisory
http://www.oracle.com/technetwork/security-advisory/cpujul2016-2881720.html Third Party Advisory
http://www.securityfocus.com/bid/81955
http://www.securityfocus.com/bid/91787 Third Party Advisory VDB Entry
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
https://blog.fuzzing-project.org/37-Mozilla-NSS-Wrong-calculation-results-in-mp_div-and-mp_exptmod.html
https://bugzilla.mozilla.org/show_bug.cgi?id=1190248 Issue Tracking
https://bugzilla.mozilla.org/show_bug.cgi?id=1194947 Issue Tracking
https://developer.mozilla.org/en-US/docs/Mozilla/Projects/NSS/NSS_3.21_release_notes Vendor Advisory
https://github.com/hannob/bignum-fuzz/blob/master/CVE-2016-1938-nss-mp_div.c
https://github.com/hannob/bignum-fuzz/blob/master/CVE-2016-1938-nss-mp_exptmod.c
https://hg.mozilla.org/projects/nss/diff/a555bf0fc23a/lib/freebl/mpi/mpi.c
https://security.gentoo.org/glsa/201605-06
https://security.gentoo.org/glsa/201701-46
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