PatchTheCVECVE-2021-27964: SonLogger before 6.4.1 is affected by Unauthenticated Arbitrary File Upload
CVE-2021-27964 is a critical-severity flaw (CVSS 9.8) 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 Unauthenticated Arbitrary File Upload. An attacker can send a POST request to /Config/SaveUploadedHotspotLogoFile without any authentication or session header. There is no check for the file extension or content of the uploaded file.
Why this priority
- Critical severity
- EPSS top 1%: very likely to be exploited
- Public exploit reference
- Remotely exploitable, no login, no user action
A fixed release or distro patch exists.
Risk facts
| CVSS score | 9.8 (Critical) |
| Attack vector | Network (remote) |
| Attack complexity | Low |
| Privileges needed | None |
| User interaction | None |
| EPSS exploit chance | 47.5% (top 1%) |
| CISA exploited list | No |
| Weakness | CWE-434 |
| Published | 2021-03-05 |
| Last modified | 2026-06-17 |
Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score
Am I affected?
Timeline
- Published CVE record published
- Updated Record last modified
Exact fixes by distribution
Public exploits and detection
Public code exists for this CVE. Treat unpatched systems as at risk, and only run PoCs in a lab.
- Write-up: github.com/erberkan/SonLogger-vulns
- Exploit-DB: SonLogger 4.2.3.3 - Unauthenticated Arbitrary File Upload (Metasploit)
- Nuclei scan template: SonLogger - Arbitrary File Upload
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-2021-27964?
sonlogger: upgrade to 6.4.1. Exact commands for each OS are on this page.
Is CVE-2021-27964 being exploited?
CVE-2021-27964 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-2021-27964 affect?
CVE-2021-27964 affects sonlogger. Severity is critical (CVSS 9.8). SonLogger before 6.4.1 is affected by Unauthenticated Arbitrary File Upload. An attacker can send a POST request to /Config/SaveUploadedHotspotLogoFile without any authentication or session header. There is no check for the file extension o
How urgent is CVE-2021-27964?
Priority 69/100. Critical severity; EPSS top 1%: very likely to be exploited; Public exploit reference; Remotely exploitable, no login, no user action
Related CVEs
- CVE-2021-27963 HIGH 8.2 UPGRADE SonLogger before 6.4.1 is affected by user creation with any user permissions profile (e.g., SuperAdmin)