CVE-2020-26251: Open Zaak is a modern, open-source data- and services-layer to enable zaakgericht werken, a Dutch approach to

Q: How do I fix CVE-2020-26251?

open zaak: upgrade to 1.3.3. Exact commands for each OS are on this page.

Q: Is CVE-2020-26251 being exploited?

CVE-2020-26251 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-2020-26251 affect?

CVE-2020-26251 affects open zaak. Severity is medium (CVSS 4.7). Open Zaak is a modern, open-source data- and services-layer to enable zaakgericht werken, a Dutch approach to case management. In Open Zaak before version 1.3.3 the Cross-Origin-Resource-Sharing policy in Open Zaak is currently wide open -

Q: How urgent is CVE-2020-26251?

Priority 26/100. No elevated risk signals yet.

Routine

MEDIUM 4.7UPGRADE

CVE-2020-26251 is a medium-severity flaw (CVSS 4.7) affecting open zaak. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Open Zaak is a modern, open-source data- and services-layer to enable zaakgericht werken, a Dutch approach to case management. In Open Zaak before version 1.3.3 the Cross-Origin-Resource-Sharing policy in Open Zaak is currently wide open - every client is allowed. This allows evil.com to run scripts that perform AJAX calls to known Open Zaak installations, and the browser will not block these. This was intended to only apply to development machin

Why this priority

No elevated risk signals yet

A fixed release or distro patch exists.

Risk facts

CVSS score	4.7 (Medium)
Attack vector	Network (remote)
Attack complexity	High
Privileges needed	None
User interaction	Required
EPSS exploit chance	0.5% (top 61%)
CISA exploited list	No
Weakness	CWE-346
Published	2020-12-18
Last modified	2026-06-17

Publisher (CNA): GitHub, Inc. · Vendor: openzaak

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

Am I affected?

Timeline

2020-12-18 18:15 UTCPublished CVE record published
2026-06-17 03:07 UTCUpdated Record last modified

openzaak open zaak UPGRADE

Affected: < 1.3.3

Fixed in: 1.3.3

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy open-zaak || rpm -q open-zaak || open-zaak --version

2. UPGRADE to 1.3.3 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade open-zaak

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade open-zaak

Note

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

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-2020-26251?

open zaak: upgrade to 1.3.3. Exact commands for each OS are on this page.

Is CVE-2020-26251 being exploited?

CVE-2020-26251 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-2020-26251 affect?

CVE-2020-26251 affects open zaak. Severity is medium (CVSS 4.7). Open Zaak is a modern, open-source data- and services-layer to enable zaakgericht werken, a Dutch approach to case management. In Open Zaak before version 1.3.3 the Cross-Origin-Resource-Sharing policy in Open Zaak is currently wide open -

How urgent is CVE-2020-26251?

Priority 26/100. No elevated risk signals yet.

References

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