CVE-2021-35211: SolarWinds Serv-U Remote Code Execution Vulnerability

Reference page built from the source records below, each shown as its source publishes it. Dataset version ref-ed0843ec4e9a, updated 2026-11-02T23:39:54.475Z.

CISA Known Exploited Vulnerabilities

Name: SolarWinds Serv-U Remote Code Execution Vulnerability
Vendor: SolarWinds
Product: Serv-U
Added to the catalog: 2021-11-03
Due date for US federal agencies: 2021-11-17
Weaknesses: CWE-787
Catalog version: 2026.10.30

SolarWinds Serv-U contains an unspecified memory escape vulnerability which can allow for remote code execution.

Required action (CISA)

Apply updates per vendor instructions.

Ransomware use: CISA marks this vulnerability as known to be used in ransomware campaigns. CISA does not say which group used it.

Links in CISA's notes

https://nvd.nist.gov/vuln/detail/CVE-2021-35211

Read on 2026-11-02T23:39:54.475Z under licence cisa-kev-cc0@b0067899 from https://www.cisa.gov/sites/default/files/feeds/known_exploited_vulnerabilities.json

NVD analysis

Status: Analyzed
Published: 2021-07-14T21:15:08.090
Last modified: 2026-06-17T03:57:18.450
Weaknesses: CWE-787

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.

Metric	Score	Severity	Vector	Scored by
CVSS 3.1	9	CRITICAL	CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:H/I:H/A:H	[email protected] (Secondary)
CVSS 3.1	10	CRITICAL	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H	[email protected] (Primary)
CVSS 2.0	10	HIGH	AV:N/AC:L/Au:N/C:C/I:C/A:C	[email protected] (Primary)

References

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

This product uses the NVD API but is not endorsed or certified by the NVD.

Read on 2026-11-02T23:41:59.479Z under licence nvd-api-terms-of-use@ff2a5288 from https://services.nvd.nist.gov/rest/json/cves/2.0?cveId=CVE-2021-35211

CVE record

Title (CNA): Serv-U Remote Memory Escape Vulnerability
Assigner: SolarWinds
State: PUBLISHED
Published: 2021-07-14T20:55:25.167Z
Updated: 2025-10-21T23:25:40.369Z
Problem types: Memory Escape Vulnerability in Solarwinds Serv-U

References

Read on 2026-11-03T01:08:17.344Z under licence cve-terms-of-use@81bfa2f3 from https://raw.githubusercontent.com/CVEProject/cvelistV5/main/cves/2021/35xxx/CVE-2021-35211.json

Detection rules (SigmaHQ)

SigmaHQ rules whose own tags name this CVE. Each rule page shows the rule as its author published it.

Suspicious Serv-U Process Pattern (status test, level high)
Serv-U Exploitation CVE-2021-35211 by DEV-0322 (status test, level critical)

Defensive techniques (MITRE D3FEND)

D3FEND maps these defensive techniques to the weakness (CWE) that NVD lists for this CVE, through the digital artifacts the weakness affects. D3FEND does not say they stop this vulnerability.

CWE-787: Out-of-bounds Write

Harden: Variable Initialization (acts on Subroutine)
Harden: Trusted Library (acts on Subroutine)
Harden: Software Update (acts on Software)
Model: Asset Vulnerability Enumeration (acts on Software)
Model: Software Inventory (acts on Software)
Harden: Domain Logic Validation (acts on Subroutine)
Harden: Credential Scrubbing (acts on Subroutine)
Isolate: Application-based Process Isolation (acts on Subroutine)
Restore: Restore Software (acts on Software)

D3FEND ontology version 1.6.0.

Read on 2026-11-03T00:02:57.820Z under licence d3fend-terms-of-use@f98cbc7e from https://d3fend.mitre.org/api/weakness/cwe/CWE-787.json

MITRE D3FEND™ knowledge graph. © 2025 The MITRE Corporation.
"The MITRE Corporation (MITRE) hereby grants you a non-exclusive, royalty-free license to use D3FEND for research, development, and commercial purposes. Any copy you make for such purposes is authorized provided that you reproduce MITRE's copyright designation and this license in any such copy." Terms: https://d3fend.mitre.org/tou/

Sources and licences

CISA
Source: CISA Catalog of Known Exploited Vulnerabilities, version 2026.10.30, CC0 1.0. Use of this data does not imply endorsement by CISA or DHS.
CC0 1.0 Universal
National Vulnerability Database (NIST)
This product uses the NVD API but is not endorsed or certified by the NVD.
NVD API Terms of Use (NIST publications in the public domain, 17 U.S.C. 105)
CVE Program, The MITRE Corporation
Copyright © 1999-2026, The MITRE Corporation. CVE is a trademark and the CVE logo is a registered trademark of The MITRE Corporation. CVE Usage: MITRE hereby grants you a perpetual, worldwide, non-exclusive, no-charge, royalty-free, irrevocable copyright license to reproduce, prepare derivative works of, publicly display, publicly perform, sublicense, and distribute Common Vulnerabilities and Exposures (CVE™). Any copy you make for such purposes is authorized provided that you reproduce MITRE's copyright designation and this license in any such copy.
CVE Program Terms of Use ("CVE Usage" licence)
SigmaHQ
"Suspicious Serv-U Process Pattern" by Florian Roth (Nextron Systems) (SigmaHQ). Rule: https://github.com/SigmaHQ/sigma/blob/ccbb0369507f796db0b0ae6854c8a2be471b9d84/rules/windows/process_creation/proc_creation_win_servu_susp_child_process.yml.
Licensed under the Detection Rule License (DRL) 1.1: https://github.com/SigmaHQ/Detection-Rule-License
Detection Rule License (DRL) 1.1
SigmaHQ
"Serv-U Exploitation CVE-2021-35211 by DEV-0322" by Florian Roth (Nextron Systems) (SigmaHQ). Rule: https://github.com/SigmaHQ/sigma/blob/ccbb0369507f796db0b0ae6854c8a2be471b9d84/rules-emerging-threats/2021/Exploits/CVE-2021-35211/proc_creation_win_exploit_cve_2021_35211_servu.yml.
Licensed under the Detection Rule License (DRL) 1.1: https://github.com/SigmaHQ/Detection-Rule-License
Detection Rule License (DRL) 1.1
MITRE D3FEND
MITRE D3FEND™ knowledge graph. © 2025 The MITRE Corporation.
"The MITRE Corporation (MITRE) hereby grants you a non-exclusive, royalty-free license to use D3FEND for research, development, and commercial purposes. Any copy you make for such purposes is authorized provided that you reproduce MITRE's copyright designation and this license in any such copy." Terms: https://d3fend.mitre.org/tou/
MITRE D3FEND Terms of Use (site + knowledge graph); source repo MIT

Cite this page

Dragons Eye Ransomware Tracker, "CVE-2021-35211: SolarWinds Serv-U Remote Code Execution Vulnerability",
entity page, dataset version ref-ed0843ec4e9a, updated 2026-11-02T23:39:54.475Z,
https://ransomware-tracker.com/cve/CVE-2021-35211 (accessed 2026-11-03).
Underlying source: CISA Catalog of Known Exploited Vulnerabilities, version 2026.10.30.
Underlying source: National Vulnerability Database (NIST), CVE API 2.0, record last modified 2026-06-17T03:57:18.450.
Underlying source: CVE List (CVE Program, The MITRE Corporation), record updated 2025-10-21T23:25:40.369Z.
Underlying source: SigmaHQ rule 58f4ea09-0fc2-4520-ba18-b85c540b0eaf, commit ccbb0369507f796db0b0ae6854c8a2be471b9d84.
Underlying source: SigmaHQ rule 75578840-9526-4b2a-9462-af469a45e767, commit ccbb0369507f796db0b0ae6854c8a2be471b9d84.
Underlying source: MITRE D3FEND, ontology version 1.6.0.

Pages change. The dataset version identifies the data, but no archive of old versions is kept, so this citation cannot be replayed later.

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