What is CVE-2021-27963?

CVE-2021-27963 is a high-severity vulnerability in Sfcyazilim Sonlogger, classified under Missing Authentication for Critical Function. CVSS score: 8.2/10. Published 2021-03-05.

How severe is CVE-2021-27963?

High severity. CVSS v3 base score is 8.2 out of 10.

Is CVE-2021-27963 known to be exploited?

14 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.

Auth bypass in Sfcyazilim Sonlogger

CVE-2021-27963

SonLogger before 6.4.1 is affected by user creation with any user permissions profile (e.g., SuperAdmin). An anonymous user can send a POST request to /User/saveUser without any authentication or session header.

Vulnerability class: Broken Authentication

Published 2021-03-05 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 8.2 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:H/A:N.

EPSS exploit prediction

EPSS: 0.024 (83.8th percentile), scored 2026-10-07.

Low probability of exploitation in the next 30 days, but still tracked. 84th percentile — 83.8% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.024 · newest: 0.024 · change: 0.000

Affected products

Sfcyazilim Sonlogger

Weakness classification (CWE)

CWE-306 — Missing Authentication for Critical Function

Public proof-of-concept exploits

References

github.com/erberkan/SonLogger-vulns (Exploit, Third Party Advisory)
www.sonlogger.com/releasenotes (Release Notes, Vendor Advisory)

Frequently asked questions

What is CVE-2021-27963?: CVE-2021-27963 is a high-severity vulnerability in Sfcyazilim Sonlogger, classified under Missing Authentication for Critical Function. CVSS score: 8.2/10. Published 2021-03-05.
How severe is CVE-2021-27963?: High severity. CVSS v3 base score is 8.2 out of 10.
Is CVE-2021-27963 known to be exploited?: 14 public proof-of-concept repositories are indexed. Not currently listed in the CISA KEV catalog.