Threats / Kaseya / CVE-2021-30116
CVE-2021-30116
· EUVD no mirror located
· GCVE no mirror located
Verified 2026-08-04
Kaseya Virtual System/Server Administrator (VSA) vulnerability
Kaseya VSA contains an information disclosure vulnerability that exposes sessionId values, enabling attackers to conduct authenticated attacks against affected systems.
Verdict
Today item, not a backlog item.
This vulnerability allows unauthenticated attackers to obtain valid session identifiers through information disclosure, bypassing authentication controls and enabling lateral movement and system compromise within VSA deployments.
CISA KEV Yes · 2021-11-035Ransomware use Flagged5EPSS 0.85735 (verify live)6CVSS 103CISA SSVC Exploitation: active · Automatable: yes · Impact: total4Exploit Public PoC / detection · nuclei template12
01
Is it exploitable?
— the evidence, ranked above the scoreReported exploitation
19 independent public reports of in-the-wild exploitation are cataloged.Distinct reporting sources (vendor, incident response, government); open them for the underlying claims.
Exploited in the wild
Listed in the CISA Known Exploited Vulnerabilities catalog (added 2021-11-03), flagged for known ransomware use.
Probability (EPSS)
EPSS 0.85735 — modeled likelihood of exploitation activity.EPSS is a daily-changing model output — open the source for today's value.
Severity / affected
CVSS 10 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H) · Affected: Kaseya, Virtual System/Server Administrator (VSA). Confirm exact fixed builds in the vendor advisory.CVSS — CNA-assigned (CVE.org), version 3.1, set at disclosure.
Weakness (CWE)
Mapped to CWE-522 Insufficiently Protected Credentials — weakness family: Authentication.CWE assignment from the public NVD record (may be stale); the weakness class drives how the flaw is exploited.
CISA SSVC (triage disposition)
Exploitation: active · Automatable: yes · Technical Impact: totalCISA's own stakeholder-specific triage inputs, published in the CVE record (CISA Coordinator role). NOTE: this is CISA's three decision points; the final Act/Attend/Track decision also requires a Mission & Well-being input not published here, so no overall decision is asserted.
Currency of the record
CISA added this to its KEV catalog 117 days after the CVE record was published.KEV lag = CISA-KEV dateAdded − CVE.org datePublished; a floor on how long the known-exploited flaw sat in the public record before the federal catalog listed it. Severity/weakness here is CNA- or CISA-assigned (current at disclosure), independent of NVD's analysis backlog.
Public exploit available
Public exploit tooling is catalogued for this CVE (a public proof-of-concept / detection template). Catalog entries: nuclei template. We link the catalog page(s) only — no payload or code is hosted or restated here.Link, never host — the catalog page is the source; basicsecurity.net does not redistribute payloads.
02
Who’s exploiting it?
— attribution turns risk into urgencyAttribution not established
No confirmed (advisory-backed) threat-actor attribution is established for this record. Absence of a named actor is not absence of compromise — see Coverage & confidence.
03
Why it matters
— the attack path, told twice: adversary, then board1
Front door — unauthenticated access narrative 1
Attacker
I extract a valid sessionId from the VSA application through information disclosure.
Business
Authentication controls are circumvented, exposing the system to unauthorized access.
2
Keys to the kingdom — privilege/identity takeover narrative 2
Attacker
I use the stolen sessionId to execute authenticated API calls and administrative actions without providing credentials.
Business
Attackers gain administrative capabilities over managed systems and infrastructure.
3
Lateral reach — past segmentation narrative 3
Attacker
I deploy malware, ransomware, or backdoors across the customer base through VSA's management capabilities.
Business
Widespread compromise of customer environments and data encryption for ransom demands.
04
What to do
— defensible action- Remediate per the vendor advisory — confirm the fixed build for your version and verify exposure.1
Say it to the boardA vulnerability with this evidence profile is a defensible budget line, not a backlog ticket — fund the change against the proof above.
05