CVE-2026-11791: A flaw was found in 389 Directory Server

Routine

MEDIUM 5.0WATCHLISTDOWNGRADEMITIGATEMITIGATE

CVE-2026-11791 is a medium-severity flaw (CVSS 5.0) affecting directory server, 389 directory server, enterprise linux. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

A flaw was found in 389 Directory Server. During schema reload, the attr_syntax_swap_ht() function unconditionally frees attribute syntax information nodes, bypassing the refcount-based deferred deletion used elsewhere in the attribute syntax subsystem. If an administrator triggers schema reload while concurrent LDAP query traffic is active, worker threads may access freed memory, resulting in use-after-free or double-free and a denial of service

Why this priority

On your watchlist

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

Risk facts

CVSS score	5.0 (Medium)
Attack vector	Network (remote)
Attack complexity	High
Privileges needed	High
User interaction	None
EPSS exploit chance	0.4% (top 72%)
CISA exploited list	No
Weakness	CWE-416
Published	2026-06-18
Last modified	2026-06-30

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

Last updated 2026-06-30 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-06-18 16:16 UTCPublished CVE record published
2026-06-30 11:16 UTCUpdated Record last modified

redhat directory server DOWNGRADE

Affected: 11.0 · 12.0 · 13.0

Fixed in: no fixed release known

Safe to downgrade to: a release before 11.0

1. Check installed version

apt-cache policy directory-server || rpm -q directory-server || directory-server --version

2. No fixed release: DOWNGRADE to a release before 11.0 (Debian / Ubuntu)

apt-cache madison directory-server sudo apt install directory-server=<VERSION_BEFORE_11.0> sudo apt-mark hold directory-server

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

dnf --showduplicates list directory-server sudo dnf downgrade directory-server-<VERSION_BEFORE_11.0> sudo dnf versionlock add directory-server

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.

redhat 389 directory server 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.

redhat enterprise linux MITIGATE

Affected: 7.0 · 8.0 · 9.0 · 10.0

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-2026-11791?

directory server: downgrade or apply the listed mitigation; 389 directory server: mitigate or apply the listed mitigation; enterprise linux: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2026-11791 being exploited?

CVE-2026-11791 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-2026-11791 affect?

CVE-2026-11791 affects directory server, 389 directory server, enterprise linux. Severity is medium (CVSS 5.0). A flaw was found in 389 Directory Server. During schema reload, the attr_syntax_swap_ht() function unconditionally frees attribute syntax information nodes, bypassing the refcount-based deferred deletion used elsewhere in the attribute synt

How urgent is CVE-2026-11791?

Priority 30/100. On your watchlist

Related CVEs

CVE-2026-15722 HIGH 7.5 DOWNGRADE MITIGATE A stack buffer overflow flaw was found in 389 Directory Server (389-ds-base)
CVE-2026-11770 HIGH 7.5 DOWNGRADE MITIGATE A flaw was found in 389 Directory Server
CVE-2026-18651 MEDIUM 5.4 DOWNGRADE MITIGATE A flaw was found in 389 Directory Server
CVE-2026-11611 MEDIUM 6.5 DOWNGRADE MITIGATE A flaw was found in 389 Directory Server
CVE-2026-14940 MEDIUM 5.3 DOWNGRADE MITIGATE A heap-buffer-overflow flaw was found in 389 Directory Server (389-ds-base)

References

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