Vulnerability report

Exploited in the wild Confirmed confidence In CISA KEV

CVE-2021-35211

Serv-U Remote Memory Escape Vulnerability

SolarWinds / Serv-U Managed File Transfer Server and Serv-U Secured FTP · affected before 15.2.3 HF1

Watch CVE-2021-35211 Browse KEV feed
Severity
CVSS 9.0 · Critical
Confidence
Confirmed
Exploit status
Exploited in the wild
EPSS
91.2%
First observed
—
Last observed
—

Decision summary

What security teams need to know first

Direct answers before the deeper technical record.

What it is

CVE-2021-35211 is an unauthenticated Serv-U Remote Memory Escape Vulnerability affecting SolarWinds Serv-U Managed File Transfer Server and Serv-U Secured FTP. Microsoft discovered a remote code execution (RCE)...

Is it exploited?

Yes. Previdian tracks this CVE as a known exploited vulnerability. Confidence is confirmed. Listed in CISA KEV.

Who is affected?

SolarWinds / Serv-U Managed File Transfer Server and Serv-U Secured FTP affected before 15.2.3 hf1.

What should we do?

Prioritize remediation. Validate affected assets and apply vendor fixes on an accelerated timeline.

Overview

Serv-U Remote Memory Escape Vulnerability

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.

SolarWinds Affected
Serv-U Managed File Transfer Server and Serv-U Secured FTP
Before 15.2.3 HF1
Published
14 Jul 2021
Exploitation Reported
03 Nov 2021
Attack vector
Remote
Complexity
High
Privileges
None
User interaction
None

Tags

nuclei_scanner malware windows ransomware cisa

CVE References

Exploitation evidence

Why Previdian marks this CVE as exploited

Third-party attestation and first-party sensor observation are shown separately so teams can judge the evidence chain.

Exploited in the wild

CISA

Recorded 03 Nov 2021

A trusted third party reported exploitation.

Used in malware

CISA

Recorded 03 Nov 2021

Malware families have been linked to exploitation of this CVE.

Proof of concept available

GitHub

Recorded 30 Sep 2021

Public scanner or PoC coverage increases practical exploitability.

Known exploited vulnerability sources

Per-source evidence links for KEV attestations are available through the Previdian Pro API.

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Source Added
CISA First 2021-11-03 00:00 UTC

Detection

Operational artifacts and observed signals

Make the evidence actionable in scanner, SOC, and edge-control workflows.

Observed signals

Request targets
User-Agents
Callback hosts
0
0
0

Request targets and User-Agents available in Pro. Callback host details available in Enterprise.

Virtual patch status

No Previdian virtual patch is currently available. Future rules ship for ModSecurity, Cloudflare, and AWS WAF.

Learn about virtual patches →

Scanner Artifacts

Scanner and exploit-framework references linked to this CVE.

Scanner Reference Detected
Nuclei https://github.com/projectdiscovery/nuclei-templates/blob/main/javascript/cves/2021/CVE-2021-35211.yaml 01 Jun 2026

Risk and context

Severity, weaknesses, and research context

CVSS v3.1

9.0 Critical

Potential damage if exploited. Separate from whether attackers are using it.

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

EPSS

91.2%

Estimated chance of exploitation in the next 30 days. Previdian's warning comes from evidence, not this score.

Weaknesses

Out-of-bounds Write CWE-787

Potential Proof of Concepts

These PoCs are unverified and could contain malware. Use at your own risk.

BishopFox/CVE-2021-35211

github · Created 2022-01-14 05:52:17 UTC · 35 stars · AI assessment 90%

SolarWinds Serv-U FTP - Remote Code Execution

nuclei · Created Unknown

Timeline

From disclosure to observed exploitation

  1. 15:34 UTC

    Nuclei template available

    Scanner coverage available

  2. 05:52 UTC

    Public PoC available

    Public proof-of-concept code published

  3. 00:00 UTC

    Added to CISA KEV

    Listed in the CISA Known Exploited Vulnerabilities catalog

  4. 00:00 UTC

    First public exploitation report

    Exploit observed in malware

  5. 20:55 UTC

    CVE published

    Vulnerability disclosed publicly

  6. 00:00 UTC

    CVE ID reserved

    Identifier reserved by the CNA

Pro API

Automate this intelligence

Confidence, exploit status, sensor telemetry, PoCs, scanner integrations, mentions, and tags are available programmatically for VM, SOC, and CTI workflows.

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  • Evidence confidence and provenance
  • First-party sensor telemetry
  • PoC and scanner references
  • Affected versions and enrichment
  • Automation-ready JSON delivery

GET /api/v2/pro/kevs/CVE-2021-35211

Free JSON includes basic KEV fields 
{
  "cve_id": "CVE-2021-35211",
  "confidence": "Confirmed",
  "cvss_score": 9.0,
  "cvss_estimated": false,
  "epss_score": 0.9116,
  "exploit_status": {
    "exploited_in_the_wild": true,
    "active_exploitation_observed": false
  },
  "sensor_telemetry": { "attempts": 0, "sensors": 0 }
}