CVE-2026-33259: Having many concurrent transfers of the same RPZ can lead to inconsistent RPZ data, use after free and/or a cr

Routine

MEDIUM 5.0UPGRADE

CVE-2026-33259 is a medium-severity flaw (CVSS 5.0) affecting recursor. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Having many concurrent transfers of the same RPZ can lead to inconsistent RPZ data, use after free and/or a crash of the recursor. Normally concurrent transfers of the same RPZ zone can only occur with a malfunctioning RPZ provider.

Why this priority

No elevated risk signals yet

A fixed release or distro patch exists.

Risk facts

CVSS score	5.0 (Medium)
Attack vector	Network (remote)
Attack complexity	High
Privileges needed	High
User interaction	None
EPSS exploit chance	0.2% (top 87%)
CISA exploited list	No
Weakness	CWE-416
Published	2026-04-22
Last modified	2026-10-26

Publisher (CNA): Open-Xchange · Vendor: powerdns

Last updated 2026-10-26 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-04-22 10:16 UTCPublished CVE record published
2026-10-26 00:10 UTCUpdated Record last modified

powerdns recursor UPGRADE

Affected: >= 5.2.0 and < 5.2.9 · >= 5.3.0 and < 5.3.6 · 5.4.0

Fixed in: 5.2.9, 5.3.6

Safe to downgrade to: a release before 5.2.0

1. Check installed version

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

2. UPGRADE to 5.2.9 (Debian / Ubuntu)

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

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade recursor

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 5.2.0 (Debian / Ubuntu)

apt-cache madison recursor sudo apt install recursor=<VERSION_BEFORE_5.2.0> sudo apt-mark hold recursor

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

dnf --showduplicates list recursor sudo dnf downgrade recursor-<VERSION_BEFORE_5.2.0> sudo dnf versionlock add recursor

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-2026-33259?

recursor: upgrade to 5.2.9, 5.3.6. Exact commands for each OS are on this page.

Is CVE-2026-33259 being exploited?

CVE-2026-33259 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-2026-33259 affect?

CVE-2026-33259 affects recursor. Severity is medium (CVSS 5.0). Having many concurrent transfers of the same RPZ can lead to inconsistent RPZ data, use after free and/or a crash of the recursor. Normally concurrent transfers of the same RPZ zone can only occur with a malfunctioning RPZ provider.

How urgent is CVE-2026-33259?

Priority 21/100. No elevated risk signals yet.

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References

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