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A Vulnerability in SolarWinds Serv-U Could Allow for Remote Code Execution

MS-ISAC ADVISORY NUMBER:

2021-086

DATE(S) ISSUED:

07/13/2021

OVERVIEW:

A vulnerability has been discovered in SolarWinds Serv-U, which could result in remote code execution. SolarWinds Serv-U is an FTP server software for secure file transfer. Successful exploitation of this vulnerability could allow for remote code execution within the context of a privileged process. Depending on the privileges associated with this application, an attacker could then install programs; view, change, or delete data; or create new accounts with full user rights. If this application has been configured to have fewer user rights on the system, exploitation of this vulnerability could have less impact than if it was configured with administrative rights.

THREAT INTELLIGENCE:

Microsoft has provided evidence of limited, targeted customer impact, though SolarWinds does not currently have an estimate of how many customers may be directly affected by the vulnerability.

SYSTEMS AFFECTED:

  • SolarWinds Serv-U versions prior to Serv-U 15.2.3 HF2

RISK:

Government:
  • Large and medium government entities: HIGH
  • Small government entities: HIGH
Businesses:
  • Large and medium business entities: HIGH
  • Small business entities: HIGH
Home Users: LOW

TECHNICAL SUMMARY:

A vulnerability has been discovered in SolarWinds Serv-U, which could result in remote code execution. SolarWinds Serv-U is prone to a remote memory escape vulnerability that can allow a threat actor to run arbitrary code within the context of a privileged process. Depending on the privileges associated with this application, an attacker could then install programs; view, change, or delete data; or create new accounts with full user rights. If this application has been configured to have fewer user rights on the system, exploitation of this vulnerability could have less impact than if it was configured with administrative rights.

RECOMMENDATIONS:

We recommend the following actions be taken:
  • Apply appropriate updates provided by SolarWinds immediately after appropriate testing.
  • Run all software as a non-privileged user (one without administrative privileges) to diminish the effects of a successful attack.
  • Remind users not to visit un-trusted websites or follow links provided by unknown or un-trusted sources.
  • Inform and educate users regarding the threats posed by hypertext links contained in emails or attachments especially from un-trusted sources.
  • Apply the Principle of Least Privilege to all systems and services.

REFERENCES:

SolarWinds:
https://www.solarwinds.com/trust-center/security-advisories/cve-2021-35211

BleepingComputer:
https://www.bleepingcomputer.com/news/security/solarwinds-patches-critical-serv-u-vulnerability-exploited-in-the-wild/

ZDNet:
https://www.zdnet.com/article/solarwinds-releases-security-advisory-after-microsoft-says-customer-targeted-through-vulnerability/

CVE:
https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-35211

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