CVE-2021-30116Known exploitationNetwork attack vector

Authentication bypass via leaked agent credentials

Published Jul 9, 2021 · Updated Aug 14, 2026

Credential disclosure in Kaseya VSA before 9.5.7 allows remote attackers to obtain authenticated web sessions through dl.asp. The public dl.asp client-download workflow exposes Windows agent credentials, then accepts them in a GET request and returns a sessionId cookie usable beyond agent services. Default on-premises exposure requires no initial account; installing the downloadable client reveals Agent_Guid and AgentPassword values that grant semi-authenticated access to further VSA functions.

CVSS severity9.8
Critical
EPSS probability85.73%
Next 30 days · Sep 16, 2026
Known exploitationReported
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Credential disclosure in Kaseya VSA before 9.5.7 allows remote attackers to obtain authenticated web sessions through dl.asp. The public dl.asp client-download workflow exposes Windows agent credentials, then accepts them in a GET request and returns a sessionId cookie usable beyond agent services. Default on-premises exposure requires no initial account; installing the downloadable client reveals Agent_Guid and AgentPassword values that grant semi-authenticated access to further VSA functions.

The record

CVE
CVE-2021-30116
Published
Jul 9, 2021
Updated
Aug 14, 2026
Vendor
Unknown vendor
Product
Unknown product
Classifications
CWE-522, T1550.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jul 2, 2021Exploitation reportedREvil ransomware exploitation of Kaseya VSA
  2. Jul 9, 2021CVE publishedPublication date reported by the CVE source.
  3. Aug 14, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Affected buildAffected product and version details are unavailable.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Affected products and versions are unavailable in this record.

Published CVSS scores

9.8NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
7.5NVDAV:N/AC:L/Au:N/C:P/I:P/A:P

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationReported
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-522Insufficiently Protected Credentials
T1550.004Use Alternate Authentication Material: Web Session Cookie

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Reported exploitation

Technologies

Your stack

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Your stack

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