What is CVE-2021-35211?
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.
The record classifies CVE-2021-35211 under weakness class CWE-787. Its CVSS v3 base vector states that the flaw is reachable remotely over the network, needs no prior authentication, needs no user interaction, and has high impact on confidentiality, integrity, availability. 1 affected-product entry is recorded, across 1 vendor, listed below. The identifier was first published 1914 days ago.
Severity and exploitation probability
- CVSS v3.1 base score
- 9 — CRITICAL
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H - EPSS (FIRST)
- 91.1% probability of exploitation in the next 30 days, higher than 99.8% of all scored CVEs
- CISA KEV
- Listed since 2021-11-03, federal remediation deadline 2021-11-17 — used in known ransomware campaigns
- Threadlinqs priority
- 10/10 — CISA lists it as used in ransomware, which Threadlinqs scores at the maximum
- Published
- 2021-07-14, last modified 2025-10-21
Is CVE-2021-35211 being exploited?
CISA added CVE-2021-35211 to the Known Exploited Vulnerabilities catalog on 2021-11-03, which means the agency holds evidence of exploitation in the wild; US federal civilian agencies had to remediate it by 2021-11-17 under BOD 22-01. CISA flags the vulnerability as one used in known ransomware campaigns. Weaponised exploit code for CVE-2021-35211 is publicly available. 4 public proof-of-concept repositories are tracked for this identifier. A ProjectDiscovery Nuclei detection template exists (javascript/cves/2021/CVE-2021-35211.yaml). It currently carries a trending score of 50 in the Threadlinqs vulnerability feed.
- BishopFox/CVE-2021-35211 (github)
- NattiSamson/Serv-U-CVE-2021-35211 (github)
- 0xhaggis/CVE-2021-35211 (github)
- trickest/cve (trickest)
Affected products and versions
- SolarWinds: Serv-U Managed File Transfer Server and Serv-U Secured FTP
How to fix CVE-2021-35211
The record marks a vendor fix as available for CVE-2021-35211. Patch reference: https://www.microsoft.com/security/blog/2021/07/13/microsoft-discovers-threat-actor-targeting-solarwinds-serv-u-software-with-0-day-exploit. Vendor advisory: https://www.microsoft.com/security/blog/2021/07/13/microsoft-discovers-threat-actor-targeting-solarwinds-serv-u-software-with-0-day-exploit. Because CVE-2021-35211 is KEV-listed, US federal civilian agencies were required to apply the vendor fix, or stop using the product, by 2021-11-17. Apply the vendor fix referenced above to every affected product listed in this record, then confirm the running version against the vendor advisory.
Threat activity tracking CVE-2021-35211
1 tracked threat in the Threadlinqs corpus references CVE-2021-35211, either in the campaign’s CVE list or as an indicator on the campaign record.
Sources
Enriched from CVE.org, NVD, FIRST EPSS, CISA KEV, GitHub Security Advisories, public proof-of-concept repositories, ProjectDiscovery Nuclei. Last verified by Threadlinqs on . This product uses the NVD API but is not endorsed or certified by the NVD.