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CVE-2021-27964

75
FAUCET Score

CVE-2021-27964 is a critical unauthenticated arbitrary file upload vulnerability affecting SonLogger versions prior to 6.4.1. Attackers can exploit this by sending a POST request to /Config/SaveUploadedHotspotLogoFile without authentication, allowing them to upload any file type due to a lack of extension or content validation. This vulnerability carries a CVSS score of 9.8, indicating a high potential for complete compromise of confidentiality, integrity, and availability. While not currently on the KEV catalog, public exploit code, including a Metasploit module, is available, and Nuclei templates exist for detection, though there is minimal community discussion or media coverage.

Impacted Technologies

VendorProductVersion(s)CPE
< 6.4.1CPE matchmatch criteria
cpe:2.3:a:sfcyazilim:sonlogger:*:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

9.8CRITICAL

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

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
HIGH
Integrity Impact
HIGH
Availability Impact
HIGH
Exploitability Score
3.9
Impact Score
5.9
CvssVersion
3.1

Exploit Intelligence

EPSS Score
47.52%
Probability of exploitation in next 30 days
EPSS Percentile
98.7%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
Nuclei: CVE-2021-27964 · Jun 11, 2025
ExploitDB: EDB-49651 · Mar 15, 2021
This CVE's current EPSS score of 0.4752 is in the 96th percentile among its peer group of 36,897 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.1 Reddit, 0.3 Bluesky, 0.3 Mastodon, and 2.4 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.3 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Remediation records are not available for this CVE.

References

packetstormsecurity.com / files/161793/SonLogger-4.2.3.3-Shell-Upload.html
ExploitThird Party AdvisoryVDB Entry
github.com / erberkan/SonLogger-vulns
ExploitThird Party Advisory
sonlogger.com / releasenotes
Release NotesVendor Advisory