CVE-2021-27964

CRITICALNVD 9.89.8—
EchelonGraph scoreMEDIUM confidence

This critical-severity CVE scores 9.8 under NVD CVSS v3. EPSS exploit probability: 48.4%, top 1% of all CVEs by exploit prediction. GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: epss, nvd
Weaponized
9.8
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS: 48%CVSS: 9.8Exploit: NoneExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

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.

CVSS v3
9.8
EG Score
9.8(medium)
EG Risk
75(Track*)
EG Risk 75/100SSVC: Track*

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity98% × 45%
Exploitation65% × 40%
Automatability30% × 15%
Action: Watch closely — could escalate to Attend.
EPSS
98.7%
KEV
Not listed

Published

March 5, 2021

Last Modified

November 21, 2024

Advisory Details (1)

Auto-updated Jun 5, 2026
No patch confirmed yet.
generic

GitHub - erberkan/SonLogger-vulns: SonLogger Vulns (CVE-2021-27963, CVE-2021-27964) · GitHub

https://github.com/erberkan/SonLogger-vulns

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 10× in last 7d / 38× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

  1. 2026-07-23 14:16 UTCEPSS rescore
  2. 2026-07-23 01:59 UTCEG score recompute
  3. 2026-07-22 22:46 UTCEG score recompute
  4. 2026-07-22 14:06 UTCEPSS rescore
  5. 2026-07-22 14:06 UTCEPSS rescore
  6. 2026-07-21 15:22 UTCEPSS rescore
  7. 2026-07-21 15:22 UTCEPSS rescore
  8. 2026-07-20 17:05 UTCEPSS rescore
  9. 2026-07-19 02:27 UTCEPSS rescore
  10. 2026-07-19 02:27 UTCEPSS rescore
  11. 2026-07-16 17:00 UTCEPSS rescore
  12. 2026-07-15 16:55 UTCEPSS rescore
  13. 2026-07-15 16:55 UTCEPSS rescore
  14. 2026-07-15 01:58 UTCEPSS rescore
  15. 2026-07-13 22:27 UTCEPSS rescore
  16. 2026-07-13 22:27 UTCEPSS rescore
  17. 2026-07-13 06:10 UTCEPSS rescore
  18. 2026-07-12 05:44 UTCEPSS rescore
  19. 2026-07-12 05:44 UTCEPSS rescore
  20. 2026-07-11 08:25 UTCEPSS rescore
  21. 2026-07-11 08:25 UTCEPSS rescore
  22. 2026-07-09 19:07 UTCEPSS rescore
  23. 2026-07-08 15:12 UTCEPSS rescore
  24. 2026-07-06 16:25 UTCEPSS rescore
  25. 2026-07-06 16:25 UTCEPSS rescore
Show 41 more
  1. 2026-07-06 02:21 UTCEPSS rescore
  2. 2026-07-06 02:21 UTCEPSS rescore
  3. 2026-07-02 16:57 UTCEPSS rescore
  4. 2026-07-01 15:03 UTCEPSS rescore
  5. 2026-06-29 14:04 UTCEPSS rescore
  6. 2026-06-28 04:54 UTCEPSS rescore
  7. 2026-06-28 04:54 UTCEPSS rescore
  8. 2026-06-27 03:06 UTCEPSS rescore
  9. 2026-06-27 03:06 UTCEPSS rescore
  10. 2026-06-25 13:48 UTCEPSS rescore
  11. 2026-06-25 13:48 UTCEPSS rescore
  12. 2026-06-24 14:03 UTCEPSS rescore
  13. 2026-06-24 14:03 UTCEPSS rescore
  14. 2026-06-23 21:31 UTCEPSS rescore
  15. 2026-06-23 21:31 UTCEPSS rescore
  16. 2026-06-21 01:58 UTCEPSS rescore
  17. 2026-06-21 01:58 UTCEPSS rescore
  18. 2026-06-18 17:51 UTCEPSS rescore
  19. 2026-06-18 17:51 UTCEPSS rescore
  20. 2026-06-17 17:51 UTCEPSS rescore
  21. 2026-06-16 17:51 UTCEPSS rescore
  22. 2026-06-15 17:46 UTCEPSS rescore
  23. 2026-06-14 23:15 UTCEPSS rescore
  24. 2026-06-12 23:10 UTCEPSS rescore
  25. 2026-06-10 22:16 UTCEPSS rescore
  26. 2026-06-08 14:15 UTCEPSS rescore
  27. 2026-06-07 15:23 UTCEPSS rescore
  28. 2026-06-07 15:23 UTCEPSS rescore
  29. 2026-06-06 13:46 UTCEPSS rescore
  30. 2026-06-06 13:46 UTCEPSS rescore
  31. 2026-06-06 13:46 UTCEPSS rescore
  32. 2026-06-05 22:45 UTCEPSS rescore
  33. 2026-06-05 22:45 UTCEPSS rescore
  34. 2026-06-05 06:09 UTCEPSS rescore
  35. 2026-06-05 06:09 UTCEPSS rescore
  36. 2026-05-31 22:29 UTCEPSS rescore
  37. 2026-05-31 22:29 UTCEPSS rescore
  38. 2026-05-27 13:39 UTCEPSS rescore
  39. 2026-05-27 13:39 UTCEPSS rescore
  40. 2026-05-26 20:09 UTCEG score recompute
  41. 2026-05-26 20:09 UTCGHSA enrichment

Publicly available exploits

(2 references)

Working exploit code is in the public domain (1 Exploit-DB entry). Defenders should treat patch urgency accordingly — public PoCs typically lead to mass-exploitation within 24-72 hours.

  • Exploit-DBEDB-49651✓ verified
    First seen Mar 15, 2021

    SonLogger 4.2.3.3 - Unauthenticated Arbitrary File Upload (Metasploit)

    Open source ↗
  • Nucleihttp/cves/2021/CVE-2021-27964.yaml
    First seen Jan 1, 2021

    SonLogger - Arbitrary File Upload

    Open source ↗

Related CVEs(same CWE)

Frequently asked(5)

What is CVE-2021-27964?
CVE-2021-27964 is a critical vulnerability published on March 5, 2021. 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.
When was CVE-2021-27964 disclosed?
CVE-2021-27964 was first published in the National Vulnerability Database on March 5, 2021, with the most recent update on November 21, 2024. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2021-27964 actively exploited?
CVE-2021-27964 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 98.7% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2021-27964?
CVE-2021-27964 has a CVSS v3 base score of 9.8 (NVD).
How do I remediate CVE-2021-27964?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2021-27964, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

Dependency Blast Radius

Explore the affected products and dependency analysis for CVE-2021-27964

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