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

Q: How do I fix CVE-2016-1938?

leap: mitigate or apply the listed mitigation; opensuse: mitigate or apply the listed mitigation; nss: upgrade to newer than 3.20.1. Exact commands for each OS are on this page.

Q: Is CVE-2016-1938 being exploited?

CVE-2016-1938 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2016-1938 affect?

CVE-2016-1938 affects leap, opensuse, nss. Severity is medium (CVSS 6.5). 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 cryptographi

Q: How urgent is CVE-2016-1938?

Priority 50/100. Remotely exploitable, no login, no user action

This month

MEDIUM 6.5REMOTEMITIGATEMITIGATEUPGRADE

CVE-2016-1938 is a medium-severity flaw (CVSS 6.5) affecting leap, opensuse, nss. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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.

Why this priority

Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	6.5 (Medium)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	3.2% (top 12%)
CISA exploited list	No
Weakness	CWE-310
Published	2016-01-31
Last modified	2026-06-17

Publisher (CNA): Mozilla Corporation · Vendor: mozilla · opensuse

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2016-01-31 18:59 UTCPublished CVE record published
2026-06-17 00:42 UTCUpdated Record last modified

opensuse leap MITIGATE

Affected: 42.1

Fixed in: no fixed release known

Safe to downgrade to: a release before 42.1

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

opensuse opensuse MITIGATE

Affected: 13.1 · 13.2

Fixed in: no fixed release known

Safe to downgrade to: a release before 13.1

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

mozilla nss UPGRADE

Affected: <= 3.20.1

Fixed in: newer than 3.20.1

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy nss || rpm -q nss || nss --version

2. UPGRADE to newer than 3.20.1 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade nss

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade nss

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

mozilla firefox UPGRADE

Affected: <= 43.0.4

Fixed in: newer than 43.0.4

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy firefox || rpm -q firefox || firefox --version

2. UPGRADE to newer than 43.0.4 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade firefox

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade firefox

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2016-1938?

leap: mitigate or apply the listed mitigation; opensuse: mitigate or apply the listed mitigation; nss: upgrade to newer than 3.20.1. Exact commands for each OS are on this page.

Is CVE-2016-1938 being exploited?

CVE-2016-1938 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2016-1938 affect?

CVE-2016-1938 affects leap, opensuse, nss. Severity is medium (CVSS 6.5). 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 cryptographi

How urgent is CVE-2016-1938?

Priority 50/100. Remotely exploitable, no login, no user action

Software pages

Mozilla Firefox vulnerabilities

Related CVEs

CVE-2018-19542 MEDIUM 6.5 DOWNGRADE MITIGATE An issue was discovered in JasPer 2.0.14
CVE-2018-19539 MEDIUM 6.5 DOWNGRADE MITIGATE An issue was discovered in JasPer 2.0.14
CVE-2016-10165 HIGH 7.1 UPGRADE MITIGATE The Type_MLU_Read function in cmstypes.c in Little CMS (aka lcms2) allows remote attackers to obtain sensitive
CVE-2015-8126 HIGH 7.5 UPGRADE MITIGATE Multiple buffer overflows in the (1) png_set_PLTE and (2) png_get_PLTE functions in libpng before 1.0.64, 1.1.
CVE-2015-7575 MEDIUM 5.9 UPGRADE MITIGATE Mozilla Network Security Services (NSS) before 3.20.2, as used in Mozilla Firefox before 43.0.2 and Firefox ES

References

← Back to latest CVEs