CVE-2018-20753
CVE-2018-20753 is a security flaw in Kaseya Virtual System/Server Administrator (VSA), remote-support software IT providers use to manage their customers’ computers. Attackers can run their own code on Kaseya Virtual System/Server Administrator (VSA). The US Cybersecurity and Infrastructure Security Agency (CISA) added it to its catalog of flaws known to be used in attacks on 13 Apr 2022, and says ransomware gangs have used it.[1]
Kaseya Virtual System/Server Administrator (VSA) is business software or equipment. Most families won’t have it, but attackers break into it to get inside companies, and from there to what those companies hold about their customers, patients and staff. Kaseya has published a fix or advice.
Description
CISA calls it a VSA remote code execution in Kaseya Virtual System/Server Administrator (VSA). In its words: “Kaseya VSA RMM allows unprivileged remote attackers to execute PowerShell payloads on all managed devices.”[1]
The CVE record adds: “Kaseya VSA RMM before R9.3 9.3.0.35, R9.4 before 9.4.0.36, and R9.5 before 9.5.0.5 allows unprivileged remote attackers to execute PowerShell payloads on all managed devices. In January 2018, attackers actively exploited this vulnerability in the wild.”[2]
It scores 9.8 out of 10 on the Common Vulnerability Scoring System, which rates it critical, scored by NVD using CVSS 3.1.[2]
Affected versions
NVD’s record doesn’t list version ranges for it; Kaseya’s advisory has them[3]. CISA names the product as Kaseya Virtual System/Server Administrator (VSA).
Most families won’t have Kaseya Virtual System/Server Administrator (VSA); it’s for whoever looks after IT at work.
Exploitation
CISA added it to its catalog of known exploited vulnerabilities on 13 Apr 2022, 1,163 days after it was made public. CISA lists a flaw only when it has reliable evidence of it being exploited, and gave US federal agencies until 4 May 2022 to fix it.[1] CISA says ransomware gangs have used it.
FIRST’s Exploit Prediction Scoring System, which estimates how likely a flaw is to be used in attacks in the next 30 days from what it sees across the internet, puts it at 30%. That’s in the top 2% of the flaws it scores.[4]
CISA assesses it as automatable: attackers can run it against many targets at once.
CISA doesn’t say who was attacked, or how.
Fix
Kaseya has published a fix or advice.[3] CISA’s required action: “Apply updates per vendor instructions.”[1]
- Check whether you use it.Kaseya Virtual System/Server Administrator (VSA) is business software or equipment, so most families won’t have it. If you run a business, or work from home on company equipment, ask whoever looks after your IT.
- Send this page to your IT person.Ask them to confirm it’s fixed, or not in use. CISA gave US government agencies until 4 May 2022 to fix it.
- If it can’t be fixed, take it offline.CISA’s advice when there’s no fix is to stop using the product, or take it off the internet, until there is one.
You can’t fix someone else’s server, but you can watch for what follows a break-in like this: a breach notice, a password reset you didn’t ask for, or a scam message that knows things it shouldn’t. HARD watches for those for you and your family.
Timeline
| Date | Event |
|---|---|
| The flaw is made public in the National Vulnerability Database, with a severity score of 9.8.[2] | |
| CISA adds it to its catalog of flaws known to be used in attacks, noting that ransomware gangs have used it.[1] | |
| CISA’s deadline for US government agencies to fix it.[1] | |
| FIRST puts the odds of it being used in attacks in the next 30 days at 30%.[4] |
See also
Other Kaseya Virtual System/Server Administrator (VSA) flaws
- CVE-2017-18362: VSA SQL injection ·
- CVE-2021-30116: information disclosure ·
Similar flaws
- CVE-2026-111357, Ivanti Connect Secure: missing authentication for critical function ·
- CVE-2026-97229, GitLab Community Edition and Enterprise Edition: integer overflow or wraparound ·
- CVE-2026-76418, Cisco Secure Firewall ASA Software and Cisco Secure FTD Software: unchecked return value to NULL pointer dereference ·
- CVE-2026-48356, Adobe Commerce and Magento: unrestricted upload of file with dangerous type ·
- CVE-2026-111497, Google Brotli: unchecked return value ·
Added the same day
- CVE-2022-24521, Microsoft Windows: CLFS driver privilege escalation ·
- CVE-2018-7602, Drupal Core: remote code execution ·
- CVE-2015-5123, Adobe Flash Player: use-after-free ·
- CVE-2015-5122, Adobe Flash Player: use-after-free ·
- CVE-2015-3113, Adobe Flash Player: heap-based buffer overflow ·
Every Kaseya flaw on CISA’s list · Everything added in April 2022
References
- ^ Cybersecurity and Infrastructure Security Agency. “Kaseya VSA Remote Code Execution Vulnerability”. Known Exploited Vulnerabilities Catalog, added 13 Apr 2022.
- ^ National Institute of Standards and Technology. “CVE-2018-20753 Detail”. National Vulnerability Database, published 5 Feb 2019.
- ^ Kaseya. Advisories and fixes: helpdesk.kaseya.com.
- ^ FIRST. “Exploit Prediction Scoring System”. EPSS 0.296, percentile 98.2, 31 Oct 2026.
- CVE Program. “CVE-2018-20753”. The official CVE record.
This article is built from CISA’s catalog (version 2026.10.30), NVD’s record and FIRST’s scores, kept in HARD’s database and checked every morning. The plain English is HARD’s.