CVE-2026-33594: A client can trigger excessive memory allocation by generating a lot of queries that are routed to an overload

Routine

MEDIUM 5.3REMOTEUPGRADE

CVE-2026-33594 is a medium-severity flaw (CVSS 5.3) affecting dnsdist. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

A client can trigger excessive memory allocation by generating a lot of queries that are routed to an overloaded DoH backend, causing queries to accumulate into a buffer that will not be released until the end of the connection.

Why this priority

Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	5.3 (Medium)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.4% (top 69%)
CISA exploited list	No
Weakness	CWE-770
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 14:16 UTCPublished CVE record published
2026-10-26 21:10 UTCUpdated Record last modified

powerdns dnsdist UPGRADE

Affected: >= 1.9.0 and < 1.9.13 · >= 2.0.0 and < 2.0.4

Fixed in: 1.9.13, 2.0.4

Safe to downgrade to: a release before 1.9.0

1. Check installed version

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

2. UPGRADE to 1.9.13 (Debian / Ubuntu)

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

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade dnsdist

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 1.9.0 (Debian / Ubuntu)

apt-cache madison dnsdist sudo apt install dnsdist=<VERSION_BEFORE_1.9.0> sudo apt-mark hold dnsdist

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

dnf --showduplicates list dnsdist sudo dnf downgrade dnsdist-<VERSION_BEFORE_1.9.0> sudo dnf versionlock add dnsdist

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-2026-33594?

dnsdist: upgrade to 1.9.13, 2.0.4. Exact commands for each OS are on this page.

Is CVE-2026-33594 being exploited?

CVE-2026-33594 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-2026-33594 affect?

CVE-2026-33594 affects dnsdist. Severity is medium (CVSS 5.3). A client can trigger excessive memory allocation by generating a lot of queries that are routed to an overloaded DoH backend, causing queries to accumulate into a buffer that will not be released until the end of the connection.

How urgent is CVE-2026-33594?

Priority 31/100. Remotely exploitable, no login, no user action

Related CVEs

CVE-2026-33257 MEDIUM 5.3 UPGRADE UPGRADE An attacker can send a web request that causes unlimited memory allocation in the internal web server, leading
CVE-2026-33597 LOW 3.7 UPGRADE PRSD detection denial of service
CVE-2026-33602 MEDIUM 6.5 UPGRADE A rogue backend can send a crafted UDP response with a query ID off by one related to the maximum configured v
CVE-2026-33593 HIGH 7.5 UPGRADE A client can trigger a divide by zero error leading to crash by sending a crafted DNSCrypt query.
CVE-2026-33598 MEDIUM 4.8 UPGRADE A cached crafted response can cause an out-of-bounds read if custom Lua code calls getDomainListByAddress() or

References

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