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Fencer Vulns
low 2.4

CVE-2023-28833 json

Unrestricted filenames for logo or favicon as admin in the theming settings in nextcloud server

published 2023-03-30 3 y ago modified 2026-06-17 4 mo ago also EUVD-2023-32465

cvss
2.4
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.8%
EPSS 0.8% chance of exploitation in 30 days, percentile 55%
public exploits
0
none known

Summary

Nextcloud server is an open source home cloud implementation. In affected versions admins of a server were able to upload a logo or a favicon and to provided a file name which was not restricted and could overwrite files in the appdata directory. Administrators may have access to overwrite these files by other means but this method could be exploited by tricking an admin into uploading a maliciously named file. It is recommended that the Nextcloud Server is upgraded to 24.0.10 or 25.0.4. Users unable to upgrade should avoid ingesting logo files from untrusted sources.

Patch / fix

  • nextcloud nextcloud_server 23.0.14, 24.0.10, 25.0.4

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2023-28833 updated

nextcloud: Multiple vulnerabilities

  • Red Hat All currently supported Red Hat products
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
partial
Assessed
20 mo ago

Exploit prediction

0.76% chance of exploitation in the next 30 days, higher than 55% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 2.4 CVSS:3.1/AV:N/AC:L/PR:H/UI:R/S:U/C:N/I:N/A:L
NVD 3.1 8.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

Affected products

  • nextcloud security-advisories

Classification

Weakness
  • CWE-22 Improper Limitation of a Pathname to a Restricted Directory
  • CWE-434 Unrestricted Upload of File with Dangerous Type

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.