CVE-2026-45281

Description

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 calendar, they would be able to view and modify it. It is recommended that the Nextcloud Server is upgraded to 33.0.3 or 32.0.9. It is recommended that the Nextcloud Enterprise Server is upgraded to 33.0.3, 32.0.9, 31.0.14.5, 30.0.17.9, 29.0.16.16, 28.0.14.17, 27.1.11.26, 26.0.13.26, 25.0.13.29, 24.0.12.34, 23.0.12.35, 22.2.10.39, or 21.0.9.23

CVSS v3.1 Score

8.1

HIGH

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N

EPSS — Exploit Prediction

0.0028

Probability of exploitation

0.20%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-639 CWE-639

Affected Products

Vendor	Product	Versions
nextcloud	nextcloud_server	32.0.0 — 32.0.9
nextcloud	nextcloud_server	33.0.0 — 33.0.3
nextcloud	nextcloud_server	21.0.0 — 21.0.9.23
nextcloud	nextcloud_server	22.0.0 — 22.2.10.39
nextcloud	nextcloud_server	23.0.0 — 23.0.12.35
nextcloud	nextcloud_server	24.0.0 — 24.0.12.34
nextcloud	nextcloud_server	25.0.0 — 25.0.13.29
nextcloud	nextcloud_server	26.0.0 — 26.0.13.26
nextcloud	nextcloud_server	27.0.0 — 27.1.11.26
nextcloud	nextcloud_server	28.0.0 — 28.0.14.17
nextcloud	nextcloud_server	29.0.0 — 29.0.16.16
nextcloud	nextcloud_server	30.0.0 — 30.0.17.9
nextcloud	nextcloud_server	31.0.0 — 31.0.14.5
nextcloud	nextcloud_server	32.0.0 — 32.0.9
nextcloud	nextcloud_server	33.0.0 — 33.0.3

References

Advisories & Patches

https://github.com/nextcloud/security-advisories/security/advisories/GHSA-hrrv-mp25-26vv https://github.com/nextcloud/server/pull/59962

Other References

https://hackerone.com/reports/3545964

Frequently Asked Questions

What is CVE-2026-45281? +

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 calendar, they would be able to view and modify it. It is recommended that the Nextcloud Server is upgraded to 33.0.3 or 32.0.9. It is recommended that the Nextcloud Enterprise Server is upgraded to 33.0.3, 32.0.9, 31.0.14.5, 30.0.17.9, 29.0.16.16, 28.0.14.17, 27.1.11.26, 26.0.13.26, 25.0.13.29, 24.0.12.34, 23.0.12.35, 22.2.10.39, or 21.0.9.23 It has a CVSS v3.1 base score of 8.1 (HIGH).

How severe is CVE-2026-45281? +

CVE-2026-45281 has a CVSS v3.1 score of 8.1 out of 10, rated HIGH. This is a high-severity vulnerability that should be prioritized for patching. The EPSS score is 0.0028, placing it in the 0th percentile for exploitation probability.

What products are affected by CVE-2026-45281? +

CVE-2026-45281 affects products from nextcloud, specifically: nextcloud_server. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2026-45281? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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