CVE-2021-27963: SonLogger before 6.4.1 is affected by user creation with any user permissions profile (e.g., SuperAdmin)

Q: How do I fix CVE-2021-27963?

sonlogger: upgrade to 6.4.1. Exact commands for each OS are on this page.

Q: Is CVE-2021-27963 being exploited?

CVE-2021-27963 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2021-27963 affect?

CVE-2021-27963 affects sonlogger. Severity is high (CVSS 8.2). 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.

Q: How urgent is CVE-2021-27963?

Priority 60/100. High severity; Public exploit reference; Remotely exploitable, no login, no user action

This week

HIGH 8.2REMOTEUPGRADE

CVE-2021-27963 is a high-severity flaw (CVSS 8.2) affecting sonlogger. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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.

Why this priority

High severity
Public exploit reference
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	8.2 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	2.4% (top 16%)
CISA exploited list	No
Weakness	CWE-306
Published	2021-03-05
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: sfcyazilim

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2021-03-05 02:15 UTCPublished CVE record published
2026-06-17 03:45 UTCUpdated Record last modified

sfcyazilim sonlogger UPGRADE

Affected: < 6.4.1

Fixed in: 6.4.1

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy sonlogger || rpm -q sonlogger || sonlogger --version

2. UPGRADE to 6.4.1 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade sonlogger

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade sonlogger

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

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-2021-27963?

sonlogger: upgrade to 6.4.1. Exact commands for each OS are on this page.

Is CVE-2021-27963 being exploited?

CVE-2021-27963 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-2021-27963 affect?

CVE-2021-27963 affects sonlogger. Severity is high (CVSS 8.2). 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.

How urgent is CVE-2021-27963?

Priority 60/100. High severity; Public exploit reference; Remotely exploitable, no login, no user action

Related CVEs

CVE-2021-27964 CRITICAL 9.8 UPGRADE SonLogger before 6.4.1 is affected by Unauthenticated Arbitrary File Upload

References

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