CVE-2025-66511

Exploitation

Assessed, none found. CISA's assessment recorded neither public exploit code nor evidence of exploitation when it was made.

SSVC decision

• ExploitationnoneCISA recorded no public exploit code and no evidence of exploitation.
• AutomatablenoAt least one step from reconnaissance to exploitation cannot be reliably automated.
• Technical ImpactpartialSuccessful exploitation gives limited control of the vulnerable component.

CISA publishes the decision points, not a final SSVC decision. The decision also depends on mission and well-being impact, which is a property of your deployment rather than of the vulnerability.

EPSS probability

0.29% probability of exploitation activity in the next 30 days.

EPSS percentile

Equal to or higher than the score of 21.8% of scored records. A rank, not a probability.

NVD base score

6.5 (CVSS v3.x), scored by the NVD independently of the CNA.

NVD CVSS vector

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

NVD analysis status

Analyzed. NVD last modified this record on 2026-10-18.

Red Hat severity

No Red Hat rating. Red Hat rates the CVEs that affect its products.

Exploit-prediction scores from FIRST. Independent scoring and analysis status from the NVD. Vendor severity from Red Hat. Exploitation assessment and catalog membership from CISA.

Published

2025-12-05 16:42Z10 MO AGO

Last updated

2025-12-05 16:53Z10 MO AGO

Reserved

2025-12-03

Assigning CNA

GitHub_M

Record state

PUBLISHED

Severity

Medium (CVSS 4.8)

CNA CVSS vector

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

Weaknesses

• CWE-330Use of Insufficiently Random ValuesClass

Data version

5.2

Document digest

3bad396ef2208d2173447138c08cc179bee22090c702d5ccfb4922ada3b3df86

• github.comhttps://github.com/nextcloud/security-advisories/security/advisories/GHSA-whm3-vv55-gf27x_refsource_CONFIRM
• github.comhttps://github.com/nextcloud/calendar/pull/7659x_refsource_MISC
• github.comhttps://github.com/nextcloud/calendar/commit/8de14ae87f321f5f09280d9895a27d54d24f33fbx_refsource_MISC
• hackerone.comhttps://hackerone.com/reports/3385434x_refsource_MISC