CVE-2021-35211
Serv-U Remote Memory Escape Vulnerability
- Published
- Updated
- Reserved
- Assigned by
- SolarWinds
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.
Exploited in the wild
CISA lists this vulnerability in its Known Exploited Vulnerabilities catalog as SolarWinds Serv-U Remote Code Execution Vulnerability.
- Added
- 3 Nov 2021
- Fix due (US federal)
- 17 Nov 2021
- Used by ransomware
- Known
Apply updates per vendor instructions.
Public exploit
An exploit or proof of concept is public: anyone can try it against an unpatched system. CISA's SSVC rates its exploitation: it is being exploited.
Timeline
ID reserved
By SolarWinds
- 22 days later
· 22 days later
Published
- 4 months later
· 4 months later
Added to CISA KEV
Known exploited, also by ransomware
- 4 years later
· 4 years later
Record updated
Changes after publication (a new score, a public exploit, EPSS crossing 1, 10 or 50 %, leaving KEV) are kept since November 2026; earlier ones are not known.
Scores
| Scored by | CVSS | Score | Vector |
|---|---|---|---|
| SolarWindsCNA (assigner) | 3.1 | Critical9.0 | CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H |
| NVDNVD · Analyzed | 3.1 | Critical10.0 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H |
- EPSS (exploitation in 30 days)
- 91.2% · top 0.2% of all CVEs (7 Nov 2026)
- CISA SSVC
- Exploitation: active · Automatable: no · Technical impact: total
The list uses the assigner's score when there is one, then CISA's, then NVD's: Critical 9.0.
Weakness
- Memory Escape Vulnerability in Solarwinds Serv-U
- CWE-787 Out-of-bounds Write (opens in a new tab)All about CWE-787 and its CVEs
Affected products
SolarWinds · Serv-U Managed File Transfer Server and Serv-U Secured FTP
- affected SolarWinds Serv-U – < 15.2.3 HF1
What to do
Solution: SolarWinds has released a hotfix 15.2.3 HF2 It is suggested to upgrade to the latest hotfix as soon as possible
Workaround: SolarWinds advises to disconnect Serv-U Server from internet until patched.
References (3)
- https://www.solarwinds.com/trust-center/security-advisories/cve-2021-35211 (opens in a new tab)x_refsource_MISCx_transferred
- https://www.microsoft.com/security/blog/2021/07/13/microsoft-discovers-threat-actor-targeting-solarwinds-serv-u-software-with-0-day-exploit (opens in a new tab)x_refsource_MISCx_transferred
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-35211 (opens in a new tab)government-resource
Sources
The same CVE in the primary databases and aggregators, to check against.
- CVE.org record (opens in a new tab)
- CVE List JSON (GitHub) (opens in a new tab)
- NVD (opens in a new tab)
- CISA KEV catalog (opens in a new tab)
- FIRST EPSS (opens in a new tab)
- OSV.dev (opens in a new tab)
- GitHub Advisories (opens in a new tab)
- CIRCL Vulnerability-Lookup (opens in a new tab)
Badge for a README or a ticket
[](https://trackcve.app/cve/CVE-2021-35211)Record last updated .