CVE-2016-6252: Integer overflow in shadow 4.2.1 allows local users to gain privileges via crafted input to newuidmap.

Routine

HIGH 7.8DOWNGRADE

CVE-2016-6252 is a high-severity flaw (CVSS 7.8) affecting shadow. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Integer overflow in shadow 4.2.1 allows local users to gain privileges via crafted input to newuidmap.

Why this priority

High severity

No fix is published yet: follow the downgrade or mitigation steps.

Risk facts

CVSS score	7.8 (High)
Attack vector	Local
Attack complexity	Low
Privileges needed	Low
User interaction	None
EPSS exploit chance	0.4% (top 65%)
CISA exploited list	No
Weakness	CWE-190
Published	2017-02-17
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: shadow project

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

Am I affected?

Timeline

2017-02-17 17:59 UTCPublished CVE record published
2026-06-17 00:50 UTCUpdated Record last modified

shadow project shadow DOWNGRADE

Affected: 4.2.1

Fixed in: no fixed release known

Safe to downgrade to: a release before 4.2.1

1. Check installed version

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

2. No fixed release: DOWNGRADE to a release before 4.2.1 (Debian / Ubuntu)

apt-cache madison shadow sudo apt install shadow=<VERSION_BEFORE_4.2.1> sudo apt-mark hold shadow

2. No fixed release: DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list shadow sudo dnf downgrade shadow-<VERSION_BEFORE_4.2.1> sudo dnf versionlock add shadow

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

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-2016-6252?

shadow: downgrade or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2016-6252 being exploited?

CVE-2016-6252 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-2016-6252 affect?

CVE-2016-6252 affects shadow. Severity is high (CVSS 7.8). Integer overflow in shadow 4.2.1 allows local users to gain privileges via crafted input to newuidmap.

How urgent is CVE-2016-6252?

Priority 36/100. High severity

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CVE-2013-4235 MEDIUM 4.7 MITIGATE MITIGATE shadow: TOCTOU (time-of-check time-of-use) race condition when copying and removing directory trees
CVE-2019-16110 HIGH 8.1 UPGRADE The network protocol of Blade Shadow though 2.13.3 allows remote attackers to take control of a Shadow instanc
CVE-2018-7169 MEDIUM 5.3 DOWNGRADE An issue was discovered in shadow 4.5
CVE-2018-16588 HIGH 7.8 UPGRADE Privilege escalation can occur in the SUSE useradd.c code in useradd, as distributed in the SUSE shadow packag

References

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