CVE-2021-35211
CriticalExploitedPublic exploitMicrosoft discovered a remote code execution (RCE) vulnerability in the SolarWinds Serv-U product utilizing a Remote Memory Escape Vulnerability.
Published Nov 11, 2021 · Updated Oct 21, 2025 · Also known as TR-21-0577, TR-21-0587, TR-21-0908
Key Facts
Patch immediately- CVE-2021-35211 is a critical-severity vulnerability (CVSS 10.0 v3.1) affecting Serv-U (Solarwinds), Serv-U Managed File Transfer Server and Serv-U Secured FTP.
- It is exploited in the wild, listed in CISA KEV, Industry KEV feed, CIRCL KEV, ENISA EUVD since Jul 13, 2021 and is known to be used in ransomware campaigns. Public exploit code is available.
- EPSS estimates a 91% probability of exploitation in the next 30 days.
- Fixed versions are available, including Serv-U Managed File Transfer Server and Serv-U Secured FTP 15.2.3 HF1, Serv-U 15.2.3.
- Brandefense priority: patch immediately, because it is listed as exploited in the wild.
CVSS v3.1
10.0
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H
EPSS (30-day exploit likelihood)
91%
Higher than 99.8% of all scored CVEs
Exploited in the wild
Yes
4 catalog listings, used by ransomware
Public exploit code
Available
Proof-of-concept or weaponized module
Get the full CVE-2021-35211 brief as a PDF
Every affected product and fixed release, exploitation status and a first 24 hours response checklist, emailed within minutes.
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.
Known-Exploited Catalog Listings
| Catalog | Added | Remediation due | Ransomware use |
|---|---|---|---|
| CISA KEV | Nov 3, 2021 | Nov 17, 2021 | Known |
| Industry KEV feed | Jul 13, 2021 | Nov 17, 2021 | Known |
| CIRCL KEV | Nov 3, 2021 | Nov 17, 2021 | Known |
| ENISA EUVD | Nov 3, 2021 | n/a | Not reported |
Required action: Apply updates per vendor instructions.
Affected Products
4 affected entries in total| Product | Affected versions | Fixed in |
|---|---|---|
| Serv-USolarwinds | 15.2.3, 15.2.3-hotfix1 | 15.2.3 |
| Serv-U Managed File Transfer Server and Serv-U Secured FTP | >= SolarWinds Serv-U | 15.2.3 HF1 |
Patched Releases
Serv-U Managed File Transfer Server and Serv-U Secured FTP
15.2.3 HF1
Serv-U
15.2.3
Timeline
Added to Industry KEV feed
Jul 13, 2021
Added to CISA KEV
Nov 3, 2021
Added to CIRCL KEV
Nov 3, 2021
Added to ENISA EUVD
Nov 3, 2021
Publicly disclosed
Nov 11, 2021
Last updated
Oct 21, 2025
Weakness Type
- CWE-787 Out-of-bounds Write
References
- advisoryhttp://feedproxy.google.com/
- advisoryhttps://beta.darkreading.com/vulnerabilities-threats/microsoft-patches-3-windows-zero-days-amid-117-cves?_mc=rss_x_drr_edt_aud_dr_x_x-rss-simple
- advisoryhttps://blog.talosintelligence.com/2021/11/microsoft-patch-tuesday-for-nov-2021.html?utm_source=feedburner&utm_medium=feed&utm_campaign=Feed:+feedburner/Talos+(Talos%E2%84%A2+Blog)Microsoft
- advisoryhttps://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-35211
- advisoryhttps://gixtools.net/2021/07/microsoft-patch-tuesday-july-2021-edition/
FAQ
Common Questions.
Microsoft discovered a remote code execution (RCE) vulnerability in the SolarWinds Serv-U product utilizing a Remote Memory Escape Vulnerability.
Affected: Serv-U (Solarwinds) versions 15.2.3, 15.2.3-hotfix1; Serv-U Managed File Transfer Server and Serv-U Secured FTP versions >= SolarWinds Serv-U. The full list is in the CVE brief.
It is exploited in the wild, listed in CISA KEV, Industry KEV feed, CIRCL KEV, ENISA EUVD since Jul 13, 2021 and is known to be used in ransomware campaigns.
Yes. It was added on Nov 3, 2021 with a federal remediation due date of Nov 17, 2021.
Public exploit code is available.
Fixed versions are available, including Serv-U Managed File Transfer Server and Serv-U Secured FTP 15.2.3 HF1, Serv-U 15.2.3.
Brandefense priority: patch immediately, because it is listed as exploited in the wild.
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