CVE-2021-35211

SolarWinds Serv-U Remote Code Execution

9.0 CRITICALActively exploited (CISA KEV)Used in ransomwareEPSS 91.2%

Published14 Jul 2021
Added to CISA KEV3 Nov 2021
Remediation due17 Nov 2021

Description

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.

CVSS 3.1 breakdown

Attack vectorNetwork

Attack complexityHigh

Privileges requiredNone

User interactionNone

ScopeChanged

ConfidentialityHigh

IntegrityHigh

AvailabilityHigh

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H

Affected products

SolarWinds Serv-u< 15.2.3 · 15.2.3

Remediation

Fixed in

SolarWinds Serv-u≥ 15.2.3

Patch & vendor advisories

References

https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-35211US Government Resource
https://www.microsoft.com/security/blog/2021/07/13/microsoft-discovers-threat-actor-targeting-solarwinds-serv-u-software-with-0-day-exploitPatchVendor Advisory
https://www.solarwinds.com/trust-center/security-advisories/cve-2021-35211PatchVendor Advisory

Related CVEs

Recent high-severity vulnerabilities sharing a weakness type.

Frequently asked

Is CVE-2021-35211 being actively exploited?

Yes. CVE-2021-35211 is listed in the CISA Known Exploited Vulnerabilities (KEV) catalog, added 3 Nov 2021. It has been used in ransomware campaigns.

How severe is CVE-2021-35211?

CVE-2021-35211 has a CVSS 3.1 base score of 9.0, rated critical. EPSS estimates a 91.2% probability of exploitation.

Which products are affected by CVE-2021-35211?

Affected products include SolarWinds Serv-u.

How do I fix CVE-2021-35211?

Upgrade affected software to a fixed version, for example SolarWinds Serv-u 15.2.3 or later, then confirm no affected versions remain in your inventory.

How Secuno handles this

Secuno correlates vulnerabilities like CVE-2021-35211 against the real software inventory on every managed device, as each hourly inventory arrives. Rather than a static severity, each match is scored in context: exploit availability, EPSS, the asset's exposure, and business criticality decide where it lands in the queue. Because it is on the CISA KEV list, a risk for it never ranks below high, and the update that fixes it moves to the Emergency patch lane. If an affected version is present anywhere across your portfolio, it surfaces automatically with a prioritised remediation path.

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Data from the NVD, CISA KEV catalog and FIRST EPSS. CVSS 3.1 base score shown where available.