CVE-2015-7853: The datalen parameter in the refclock driver in NTP 4.2.x before 4.2.8p4, and 4.3.x before 4.3.77 allows remot

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CRITICAL 9.8REMOTEUPGRADEMITIGATEMITIGATE

CVE-2015-7853 is a critical-severity flaw (CVSS 9.8) affecting ntp, oncommand balance, oncommand performance manager. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

The datalen parameter in the refclock driver in NTP 4.2.x before 4.2.8p4, and 4.3.x before 4.3.77 allows remote attackers to execute arbitrary code or cause a denial of service (crash) via a negative input value.

Why this priority

Critical severity
EPSS top 4%: very likely to be exploited
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	9.8 (Critical)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	11.8% (top 4%)
CISA exploited list	No
Weakness	CWE-120
Published	2017-08-07
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: netapp · ntp

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

Am I affected?

Timeline

2017-08-07 20:29 UTCPublished CVE record published
2026-06-17 00:33 UTCUpdated Record last modified

ntp ntp UPGRADE

Affected: >= 4.2.0 and < 4.2.8 · >= 4.3.0 and < 4.3.77 · 4.2.8 · 4.2.8 p1 · 4.2.8 p1-beta1 · 4.2.8 p1-beta2 · 4.2.8 p1-beta3 · 4.2.8 p1-beta4

Fixed in: 4.2.8, 4.3.77

Safe to downgrade to: a release before 4.2.0

1. Check installed version

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

2. UPGRADE to 4.2.8 (Debian / Ubuntu)

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

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade ntp

Note

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

3. If no update is available yet, DOWNGRADE to a release before 4.2.0 (Debian / Ubuntu)

apt-cache madison ntp sudo apt install ntp=<VERSION_BEFORE_4.2.0> sudo apt-mark hold ntp

3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list ntp sudo dnf downgrade ntp-<VERSION_BEFORE_4.2.0> sudo dnf versionlock add ntp

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.

netapp oncommand balance MITIGATE

Affected: all versions

Fixed in: no fixed release known

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy oncommand-balance || rpm -q oncommand-balance || oncommand-balance --version

No fixed or unaffected release known

Apply the vendor mitigation from the advisory, disable the affected feature, or restrict network access.

netapp oncommand performance manager MITIGATE

Affected: all versions

Fixed in: no fixed release known

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy oncommand-performance-manager || rpm -q oncommand-performance-manager || oncommand-performance-manager --version

No fixed or unaffected release known

Apply the vendor mitigation from the advisory, disable the affected feature, or restrict network access.

netapp oncommand unified manager MITIGATE

Affected: all versions

Fixed in: no fixed release known

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy oncommand-unified-manager || rpm -q oncommand-unified-manager || oncommand-unified-manager --version

No fixed or unaffected release known

Apply the vendor mitigation from the advisory, disable the affected feature, or restrict network access.

netapp clustered data ontap MITIGATE

Affected: all versions

Fixed in: no fixed release known

Safe to downgrade to: no unaffected older release

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.

netapp data ontap MITIGATE

Affected: all versions

Fixed in: no fixed release known

Safe to downgrade to: no unaffected older release

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.

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-2015-7853?

ntp: upgrade to 4.2.8, 4.3.77; oncommand balance: mitigate or apply the listed mitigation; oncommand performance manager: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2015-7853 being exploited?

CVE-2015-7853 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-2015-7853 affect?

CVE-2015-7853 affects ntp, oncommand balance, oncommand performance manager. Severity is critical (CVSS 9.8). The datalen parameter in the refclock driver in NTP 4.2.x before 4.2.8p4, and 4.3.x before 4.3.77 allows remote attackers to execute arbitrary code or cause a denial of service (crash) via a negative input value.

How urgent is CVE-2015-7853?

Priority 63/100. Critical severity; EPSS top 4%: very likely to be exploited; Remotely exploitable, no login, no user action

Related CVEs

CVE-2023-26555 MEDIUM 6.4 DOWNGRADE praecis_parse in ntpd/refclock_palisade.c in NTP 4.2.8p15 has an out-of-bounds write
CVE-2023-26554 MEDIUM 5.6 DOWNGRADE mstolfp in libntp/mstolfp.c in NTP 4.2.8p15 has an out-of-bounds write when adding a '\0' character
CVE-2023-26553 MEDIUM 5.6 DOWNGRADE mstolfp in libntp/mstolfp.c in NTP 4.2.8p15 has an out-of-bounds write when copying the trailing number
CVE-2023-26552 MEDIUM 5.6 DOWNGRADE mstolfp in libntp/mstolfp.c in NTP 4.2.8p15 has an out-of-bounds write when adding a decimal point
CVE-2023-26551 MEDIUM 5.6 DOWNGRADE mstolfp in libntp/mstolfp.c in NTP 4.2.8p15 has an out-of-bounds write in the cp<cpdec while loop

References

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