How severe is CVE-2021-27964?

CVE-2021-27964 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2021-27964 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 46% (99th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-27964?

CVE-2021-27964 affects Sfcyazilim Sonlogger. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2021-27964?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.

When was CVE-2021-27964 published?

CVE-2021-27964 was published on 2021-03-05 and last updated on 2026-06-17.

CVE-2021-27964

CVE-2021-27964 is a critical-severity vulnerability in Sfcyazilim Sonlogger with a CVSS 3.x base score of 9.8. Its EPSS exploit-prediction score of 46% places it in the 99th percentile, indicating an elevated likelihood of exploitation. The underlying weakness is classified as CWE-434.

Key facts

Severity: Critical (CVSS 3.x base score 9.8)
CVSS v2: 7.5
EPSS exploit prediction: 46% (99th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-434
Affected product: Sfcyazilim Sonlogger
Published: 2021-03-05
Last modified: 2026-06-17

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.

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.
How severe is CVE-2021-27964?: CVE-2021-27964 has a CVSS 3.x base score of 9.8, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2021-27964 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 46% (99th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-27964?: CVE-2021-27964 affects Sfcyazilim Sonlogger. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2021-27964?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.
When was CVE-2021-27964 published?: CVE-2021-27964 was published on 2021-03-05 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:sfcyazilim:sonlogger:*:*:*:*:*:*:*:*

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