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ExploitedNot in CISA KEV yetFix available

CVE-2021-27964

Exploitation confirmed. First attested on 2023-10-14 by GCVE · kevintel, GCVE · shadowserver.

  • Published2021-03-05
  • Fixed in6.4.1
  • WeaknessCWE-434

Am I affected?

With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.

Description

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.

Timeline

dates in UTC
  1. 2021-03-0502:15CVE publishedNVD
  2. 2021-03-15Exploit-DB entryExploit-DB
  3. 2023-10-1414:56Listed as exploited by GCVEGCVE
  4. 2023-10-1414:56Exploitation first reportedGCVE

Observed activity

isMalicious corpus · updated 2026-11-03 21:37 UTC
Indicators tagged with this CVE, per day0 indicators over 7 days
Block these indicators
  • Firewall list (EDL, text): https://api.ismalicious.com/edl/cve/CVE-2021-27964?format=txt
  • CSV export: https://api.ismalicious.com/edl/cve/CVE-2021-27964?format=csv
  • TAXII collection of exploited CVEs
  • The EDL and CSV take an API key on the Pro plan.

Versions per branch

NVD
Sfcyazilim sonlogger
BranchAffectedFixed in
6.4< 6.4.16.4.1

as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.

Fix

  1. Update Sfcyazilim sonlogger to 6.4.1

Advisories and patches

Detection

read 2026-11-03 22:42 UTC
Nuclei template
available
ProjectDiscovery
Exploit-DB
EDB-49651
Exploit-DB
Proof-of-concept repositories
none listed
PoC-in-GitHub
Metasploit modules
none listed
Metasploit Framework

Sources

Identifiers

Technical details

CVSS v3 Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Published
2021-03-05
Last Modified
2026-06-17
NVD status
Modified

Frequently asked questions

What is CVE-2021-27964?

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.

Is CVE-2021-27964 actively exploited?

Active exploitation of CVE-2021-27964 has not been confirmed. Its EPSS score was 47.5% on 2026-11-03, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2021-27964?

CVE-2021-27964 has a CVSS v3 base score of 9.8 (CRITICAL severity), with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.

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Sources for this record