CVE-2021-35211
Serv-U Remote Memory Escape Vulnerability
Exploited in the wild. In CISA KEV since 2021‑11‑03. Fixed versions are out.
What to do
Find your product and version, then upgrade to the build on the right.
- SolarWinds Serv-U Managed File Transfer Server and Serv-U Secured FTPAffected: ≥ SolarWinds Serv-U, < 15.2.3 HF1Upgrade to: 15.2.3 HF1Stated by: CVE record
- Solarwinds Serv-uAffected: < 15.2.3Upgrade to: 15.2.3Stated by: NVD
- SolarWinds Inc. Serv-U File ServerAffected: до 15.2.3 HF2Upgrade to: not statedStated by: BDU
Versions as the sources state them. Full version matrix after sign-in
Coverage timeline
2 publishersAdvisory coverage
Exploitation reported in the wild
Added to CISA KEV catalog
Sourced from public security reporting — each date is when it was published, not when it happened.
What it is
From the CVE record
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.
In plain language
No plain-language summary for this CVE yet.
Exploitation
Where each signal puts this CVE on the scale from published to confirmed exploited.
- CISA KEV
Listed as exploited in the wild since 2021-11-03.
US federal agencies must remediate by 2021-11-17.
Known use in ransomware campaigns.
Apply updates per vendor instructions.
- Public exploits
No public exploit or proof of concept found in the sources we track.
- EPSS
91% chance of exploitation activity in the next 30 days, which ranks it in the 99th percentile of scored CVEs.
Exploit Prediction Scoring System, FIRST.org. A probability, not a confirmation.
Lifecycle
9 events over 1807 days, from the signal feeds we watch.
- OpenVAS check added
- Nuclei check added
- Patch availableworkaround available, record updated
- Added to CISA KEVransomware campaign
- Publishedweakness classified, att&ck mapped
Affected products
Technical detail
CVSS 3.1 vector
Open in the CVSS calculatorCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H
Scored 9.0 by NVD.
How it is reached
- Attack Vector NetworkExploitable remotely over the network without any special conditions
- Attack Complexity HighRequires specific conditions like a race condition or non-default configuration
- Privileges Required NoneNo authentication required — anyone can exploit this
- User Interaction NoneNo user interaction needed — fully automated exploitation
Scope
- Scope ChangedThe exploit can affect other components (e.g. sandbox escape, host compromise from VM)
Impact if exploited
- Confidentiality HighTotal information disclosure — all data in the component is compromised
- Integrity HighTotal loss of integrity — attacker can modify any data in the component
- Availability HighTotal denial of service — the component is completely unavailable
Weaknesses
ATT&CK techniques
Mapped from the weaknesses above (CWE to ATT&CK), not observed in attacks.
- Initial AccessT1190Exploit Public-Facing Applicationhigh confidence
- Privilege EscalationT1068Exploitation for Privilege Escalationhigh confidence
Sources
References in the record
- solarwinds.com/trust-center/security-advisories/cve-2021-35211
- microsoft.com/security/blog/2021/07/13/microsoft-discovers-threat-actor-targeting-solarwinds-serv-u-software-with-0-day-exploit
- cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-35211
And 4 more references. See all after sign-in
In the news
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