CVE-2021-4091: A double-free was found in the way 389-ds-base handles virtual attributes context in persistent searches

Q: How do I fix CVE-2021-4091?

389-ds-base: upgrade to 1.3.10.2; enterprise linux desktop: mitigate or apply the listed mitigation; enterprise linux for ibm z systems: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Q: Is CVE-2021-4091 being exploited?

CVE-2021-4091 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-2021-4091 affect?

CVE-2021-4091 affects 389-ds-base, enterprise linux desktop, enterprise linux for ibm z systems. Severity is high (CVSS 7.5). A double-free was found in the way 389-ds-base handles virtual attributes context in persistent searches. An attacker could send a series of search requests, forcing the server to behave unexpectedly, and crash.

Q: How urgent is CVE-2021-4091?

Priority 56/100. High severity; Remotely exploitable, no login, no user action; On your watchlist

This month

HIGH 7.5REMOTEWATCHLISTUPGRADEMITIGATEMITIGATE

CVE-2021-4091 is a high-severity flaw (CVSS 7.5) affecting 389-ds-base, enterprise linux desktop, enterprise linux for ibm z systems. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

A double-free was found in the way 389-ds-base handles virtual attributes context in persistent searches. An attacker could send a series of search requests, forcing the server to behave unexpectedly, and crash.

Why this priority

High severity
Remotely exploitable, no login, no user action
On your watchlist

A fixed release or distro patch exists.

Risk facts

CVSS score	7.5 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	2.0% (top 19%)
CISA exploited list	No
Weakness	CWE-415
Published	2022-02-18
Last modified	2026-06-17

Publisher (CNA): Red Hat, Inc. · Vendor: port389 · redhat

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

Am I affected?

Timeline

2022-02-18 18:15 UTCPublished CVE record published
2026-06-17 04:19 UTCUpdated Record last modified

port389 389-ds-base UPGRADE

Affected: < 1.3.10.2

Fixed in: 1.3.10.2

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy 389-ds-base || rpm -q 389-ds-base || 389-ds-base --version

2. UPGRADE to 1.3.10.2 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade 389-ds-base

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade 389-ds-base

Note

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

redhat enterprise linux desktop MITIGATE

Affected: 7

Fixed in: no fixed release known

Safe to downgrade to: a release before 7

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.

redhat enterprise linux for ibm z systems MITIGATE

Affected: 7.0

Fixed in: no fixed release known

Safe to downgrade to: a release before 7.0

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.

redhat enterprise linux for power big endian MITIGATE

Affected: 7.0

Fixed in: no fixed release known

Safe to downgrade to: a release before 7.0

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.

redhat enterprise linux for power little endian MITIGATE

Affected: 7.0

Fixed in: no fixed release known

Safe to downgrade to: a release before 7.0

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.

redhat enterprise linux for scientific computing MITIGATE

Affected: 7.0

Fixed in: no fixed release known

Safe to downgrade to: a release before 7.0

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-2021-4091?

389-ds-base: upgrade to 1.3.10.2; enterprise linux desktop: mitigate or apply the listed mitigation; enterprise linux for ibm z systems: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2021-4091 being exploited?

CVE-2021-4091 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-2021-4091 affect?

CVE-2021-4091 affects 389-ds-base, enterprise linux desktop, enterprise linux for ibm z systems. Severity is high (CVSS 7.5). A double-free was found in the way 389-ds-base handles virtual attributes context in persistent searches. An attacker could send a series of search requests, forcing the server to behave unexpectedly, and crash.

How urgent is CVE-2021-4091?

Priority 56/100. High severity; Remotely exploitable, no login, no user action; On your watchlist

Related CVEs

CVE-2022-2850 MEDIUM 6.5 DOWNGRADE MITIGATE A flaw was found In 389-ds-base
CVE-2022-0918 HIGH 7.5 DOWNGRADE MITIGATE A vulnerability was discovered in the 389 Directory Server that allows an unauthenticated attacker with networ
CVE-2021-3652 MEDIUM 6.5 UPGRADE A flaw was found in 389-ds-base

References

← Back to latest CVEs