CVE-2026-45281: Nextcloud is an open source content collaboration platform

Routine

HIGH 8.1UPGRADE

CVE-2026-45281 is a high-severity flaw (CVSS 8.1) affecting nextcloud server. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Nextcloud is an open source content collaboration platform. In Nextcloud Server from versions 32.0.0 to before 32.0.9, and 33.0.0 to before 33.0.3, with the knowledge of other users’ principal URL an attacker could possibly send a request to gain full access to their calendar. Therefore, the attacker must be an authenticated user. This is because of improper authorization controls in the backend of the calendar. If the attacker had access to the

Why this priority

High severity

A fixed release or distro patch exists.

Risk facts

CVSS score	8.1 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	Low
User interaction	None
EPSS exploit chance	0.3% (top 79%)
CISA exploited list	No
Weakness	CWE-639
Published	2026-06-01
Last modified	2026-07-22

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

Last updated 2026-07-22 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-06-01 19:16 UTCPublished CVE record published
2026-07-22 07:10 UTCUpdated Record last modified

nextcloud nextcloud server UPGRADE

Affected: >= 32.0.0 and < 32.0.9 · >= 33.0.0 and < 33.0.3 · >= 21.0.0 and < 21.0.9.23 · >= 22.0.0 and < 22.2.10.39 · >= 23.0.0 and < 23.0.12.35 · >= 24.0.0 and < 24.0.12.34 · >= 25.0.0 and < 25.0.13.29 · >= 26.0.0 and < 26.0.13.26

Fixed in: 21.0.9.23, 22.2.10.39, 23.0.12.35, 24.0.12.34, 25.0.13.29, 26.0.13.26, 27.1.11.26, 28.0.14.17, 29.0.16.16, 30.0.17.9, 31.0.14.5, 32.0.9, 33.0.3

Safe to downgrade to: a release before 21.0.0

1. Check installed version

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

2. UPGRADE to 21.0.9.23 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade nextcloud-server

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade nextcloud-server

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 21.0.0 (Debian / Ubuntu)

apt-cache madison nextcloud-server sudo apt install nextcloud-server=<VERSION_BEFORE_21.0.0> sudo apt-mark hold nextcloud-server

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

dnf --showduplicates list nextcloud-server sudo dnf downgrade nextcloud-server-<VERSION_BEFORE_21.0.0> sudo dnf versionlock add nextcloud-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.

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-2026-45281?

nextcloud server: upgrade to 21.0.9.23, 22.2.10.39, 23.0.12.35, 24.0.12.34, 25.0.13.29, 26.0.13.26, 27.1.11.26, 28.0.14.17, 29.0.16.16, 30.0.17.9, 31.0.14.5, 32.0.9, 33.0.3. Exact commands for each OS are on this page.

Is CVE-2026-45281 being exploited?

CVE-2026-45281 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-2026-45281 affect?

CVE-2026-45281 affects nextcloud server. Severity is high (CVSS 8.1). Nextcloud is an open source content collaboration platform. In Nextcloud Server from versions 32.0.0 to before 32.0.9, and 33.0.0 to before 33.0.3, with the knowledge of other users’ principal URL an attacker could possibly send a request t

How urgent is CVE-2026-45281?

Priority 34/100. High severity

Software pages

Nextcloud vulnerabilities

Related CVEs

CVE-2026-45285 MEDIUM 6.4 UPGRADE Nextcloud is an open source content collaboration platform
CVE-2026-45810 MEDIUM 6.8 UPGRADE Nextcloud is an open source content collaboration platform
CVE-2026-45690 MEDIUM 5.9 UPGRADE Nextcloud is an open source content collaboration platform
CVE-2026-45691 MEDIUM 5.9 UPGRADE Nextcloud is an open source content collaboration platform
CVE-2026-45282 MEDIUM 6.5 UPGRADE Nextcloud is an open source content collaboration platform

References

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