CVE-2021-35211
SolarWinds Serv-U Remote Code Execution Vulnerability
SolarWinds Serv-U
Microsoft discovered a remote code execution (RCE) vulnerability in the SolarWinds Serv-U product utilizing a Remote Memory Escape Vulnerability. If exploited, a threat actor may be able to gain privileged access to the machine hosting Serv-U Only. SolarWinds Serv-U Managed File Transfer and Serv-U Secure FTP for Windows before 15.2.3 HF2 are affected by this vulnerability.
Ransomware groups exploiting CVE-2021-35211
The ransomware group known as Cl0p is a variant of a previously known strain dubbed CryptoMix. It is worth noting that this variant was delivered as the final payload in a phishing campaign in 2019 and was exclusively financially motivated, with attacks carrie
Exploitation is attributed to these groups across their recorded activity. It does not follow that every organisation they listed was reached through CVE-2021-35211 — the source data does not record an entry point per incident.
Exploitation status
CISA Known Exploited Vulnerabilities
Listed by CISA on 3 November 2021. US federal agencies were required to remediate it by 17 November 2021. CISA records this vulnerability as known to be used in ransomware campaigns.
EPSS — exploitation probability
FIRST puts the probability of exploitation activity in the next 30 days at 91.2%, which is higher than 99.8% of all scored vulnerabilities. EPSS is a forecast of activity, not a measure of severity, and it is rescored daily.
CVSS vector
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H
Recent listings by these groups
Disclosures from the groups above, newest first.
Frequently asked questions
Is CVE-2021-35211 being exploited by ransomware groups?
Yes. CVE-2021-35211 is recorded as exploited by Clop. Between them these groups account for 783 victim disclosures in this database. CISA also records this vulnerability as used in ransomware campaigns.
What does CVE-2021-35211 affect?
CVE-2021-35211 affects SolarWinds Serv-U. Microsoft discovered a remote code execution (RCE) vulnerability in the SolarWinds Serv-U product utilizing a Remote Memory Escape Vulnerability. If exploited, a threat actor may be able to gain privileged access to the machine hosting Serv-U Only. SolarWinds Serv-U Managed File Transfer and Serv-U Secure FTP for Windows before 15.2.3 HF2 are affected by this vulnerability.
How severe is CVE-2021-35211?
CVE-2021-35211 is rated CRITICAL with a CVSS base score of 9. EPSS puts the probability of exploitation in the next 30 days at 91.2%, higher than 99.8% of all scored vulnerabilities. It is listed in the CISA Known Exploited Vulnerabilities catalog, with a federal remediation deadline of 17 November 2021.
How should organisations respond to CVE-2021-35211?
Apply the vendor patch for SolarWinds Serv-U as the first priority, and treat any internet-facing instance as the most urgent. Because this vulnerability is associated with ransomware activity, also review whether the affected systems were reachable before patching, rather than assuming that patching alone closes the incident.