PatchTheCVECVE-2026-33257: An attacker can send a web request that causes unlimited memory allocation in the internal web server, leading
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Routine
MEDIUM 5.3REMOTEUPGRADEUPGRADEUPGRADE
CVE-2026-33257 is a medium-severity flaw (CVSS 5.3) affecting authoritative, dnsdist, recursor. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.
An attacker can send a web request that causes unlimited memory allocation in the internal web server, leading to a denial of service. The internal web server is disabled by default.
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 | 0.5% (top 57%) |
| 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
- Published CVE record published
- Updated Record last modified
powerdns authoritative UPGRADE
Affected: >= 4.9.0 and < 4.9.14 · >= 5.0.0 and < 5.0.4
Fixed in: 4.9.14, 5.0.4
Safe to downgrade to: a release before 4.9.0
1. Check installed version
apt-cache policy authoritative || rpm -q authoritative || authoritative --version
2. UPGRADE to 4.9.14 (Debian / Ubuntu)
sudo apt update && sudo apt install --only-upgrade authoritative
2. UPGRADE (RHEL / Amazon Linux / Fedora)
sudo dnf upgrade authoritative
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 4.9.0 (Debian / Ubuntu)
apt-cache madison authoritative
sudo apt install authoritative=<VERSION_BEFORE_4.9.0>
sudo apt-mark hold authoritative
3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)
dnf --showduplicates list authoritative
sudo dnf downgrade authoritative-<VERSION_BEFORE_4.9.0>
sudo dnf versionlock add authoritative
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.
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.
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.
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-2026-33257?
authoritative: upgrade to 4.9.14, 5.0.4; dnsdist: upgrade to 1.9.13, 2.0.4; recursor: upgrade to 5.2.9, 5.3.6. Exact commands for each OS are on this page.
Is CVE-2026-33257 being exploited?
CVE-2026-33257 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-2026-33257 affect?
CVE-2026-33257 affects authoritative, dnsdist, recursor. Severity is medium (CVSS 5.3). An attacker can send a web request that causes unlimited memory allocation in the internal web server, leading to a denial of service. The internal web server is disabled by default.
How urgent is CVE-2026-33257?
Priority 34/100. Remotely exploitable, no login, no user action
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