CVE-2021-35242Network attack vector

Cross-site request forgery via incomplete session request

Published Dec 6, 2021 · Updated Aug 4, 2024

Cross-site request forgery in SolarWinds Serv-U before 15.2.5 allows remote attackers to obtain a valid CSRF token via a crafted request. The web request handler issues a valid CSRFToken when supplied only a Session value instead of rejecting the incomplete request. Exploitation requires user interaction and can submit requests through the victim's authenticated session, but SolarWinds has not disclosed the specific actions exposed.

CVSS severity8.3
High
EPSS probability0.73%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Cross-site request forgery in SolarWinds Serv-U before 15.2.5 allows remote attackers to obtain a valid CSRF token via a crafted request. The web request handler issues a valid CSRFToken when supplied only a Session value instead of rejecting the incomplete request. Exploitation requires user interaction and can submit requests through the victim's authenticated session, but SolarWinds has not disclosed the specific actions exposed.

The record

CVE
CVE-2021-35242
Published
Dec 6, 2021
Updated
Aug 4, 2024
Vendor
SolarWinds
Product
Serv-U File Server
Classifications
CWE-352, CAPEC-62, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Dec 6, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=15.2.4 Hotfix 1 and previous versions <15.2.5

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

SolarWinds · Serv-U File Serverversion=15.2.4 Hotfix 1 and previous versions <15.2.5

Published CVSS scores

8.8NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
6.8NVDAV:N/AC:M/Au:N/C:P/I:P/A:P
8.3SolarWindsCVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:C/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-352Cross-Site Request Forgery (CSRF)
CAPEC-62Cross Site Request Forgery
T1190Exploit Public-Facing Application

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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