Kaseya VSA dl.asp Credential Disclosure and Authentication Bypass
CVE-2021-30116 affects Kaseya VSA before 9.5.7. The on-premises product exposes a default client download page at /dl.asp. An attacker can download and install a Windows agent client, which generates a KaseyaD.ini file containing an Agent_Guid and AgentPassword. Those credentials can then be supplied to /dl.asp, including via a GET request, to authenticate as an agent and obtain a sessionId cookie. The issue is therefore a credential disclosure flaw combined with improper separation of agent-facing and broader application authentication contexts, enabling authentication bypass for functionality not intended to be accessible to agents. The vulnerability was reported as exploited in the wild during the July 2021 Kaseya VSA compromise.
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Impact, mitigation & remediation
What it means. What to do now. Patch path, mitigations, and the assume-compromise checklist.
Impact
What an attacker gets, and what they’ve been doing with it.
Mitigation
If you can’t patch tonight, do this now.
Remediation
Patch, then assume compromise.
Exploits
No public exploits tracked yet. Mallory keeps watching.
No public exploit code observed for this vulnerability.
Affected products & vendors
Products and vendors Mallory has correlated with this vulnerability. Open in Mallory to drill down to specific CPE configurations and version ranges.
Vendor-confirmed product mapping. Mallory continuously reconciles this list against your asset inventory.
Recent activity
5 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.
A Kaseya VSA vulnerability referenced as previously targeted by REvil affiliates to gain initial access.
A zero-day vulnerability in Kaseya VSA used in the 2021 supply-chain compromise to bypass authentication and gain access to VSA servers, enabling downstream ransomware deployment.
A zero-day vulnerability in Kaseya VSA software that allowed attackers to bypass authentication and execute arbitrary commands, leading to ransomware deployment.
The version that knows your environment.
Query your assets running an affected version, and investigate the blast radius.
Every observed campaign linking this CVE to a named adversary.
Malware families riding this exploit, with evidence and IOCs.
YARA, Sigma, Snort, and vendor rules, auto-deployed to your SIEM.
Cross-references every affected SKU, including bundled OEM variants.
Community discussion across Reddit, Mastodon, and other social sources.