CVE-2021-35247
MediumExploitedPublic exploitServ-U web login screen to LDAP authentication was allowing characters that were not sufficiently sanitized.
Published Jan 21, 2022 · Updated Oct 21, 2025 · Also known as TR-22-0070, TR-22-0075
Key Facts
Patch immediately- CVE-2021-35247 is a medium-severity vulnerability (CVSS 5.3 v3.1) affecting Serv-U (Solarwinds).
- It is exploited in the wild, listed in CISA KEV, Industry KEV feed, CIRCL KEV, ENISA EUVD since Jan 19, 2022. Public exploit code is available.
- EPSS estimates a 3.5% probability of exploitation in the next 30 days.
- Fixed versions are available, including Serv-U 15.3.
- Brandefense priority: patch immediately, because it is listed as exploited in the wild.
CVSS v3.1
5.3
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
EPSS (30-day exploit likelihood)
3.5%
Higher than 88.8% of all scored CVEs
Exploited in the wild
Yes
4 catalog listings
Public exploit code
Available
Proof-of-concept or weaponized module
Get the full CVE-2021-35247 brief as a PDF
Every affected product and fixed release, exploitation status and a first 24 hours response checklist, emailed within minutes.
Description
Serv-U web login screen to LDAP authentication was allowing characters that were not sufficiently sanitized. SolarWinds has updated the input mechanism to perform additional validation and sanitization. Please Note: No downstream affect has been detected as the LDAP servers ignored improper characters. To insure proper input validation is completed in all environments. SolarWinds recommends scheduling an update to the latest version of Serv-U.
Known-Exploited Catalog Listings
| Catalog | Added | Remediation due | Ransomware use |
|---|---|---|---|
| CISA KEV | Jan 21, 2022 | Feb 4, 2022 | Not reported |
| Industry KEV feed | Jan 19, 2022 | Feb 4, 2022 | Not reported |
| CIRCL KEV | Jan 21, 2022 | Feb 4, 2022 | Not reported |
| ENISA EUVD | Jan 21, 2022 | n/a | Not reported |
Required action: Apply updates per vendor instructions.
Affected Products
2 affected entries in total| Product | Affected versions | Fixed in |
|---|---|---|
| Serv-USolarwinds | >= 15.2.5 and previous versions | 15.3 |
Patched Releases
Serv-U
15.3
Timeline
Added to Industry KEV feed
Jan 19, 2022
Publicly disclosed
Jan 21, 2022
Added to CISA KEV
Jan 21, 2022
Added to CIRCL KEV
Jan 21, 2022
Added to ENISA EUVD
Jan 21, 2022
Last updated
Oct 21, 2025
Weakness Type
- CWE-20 Improper Input Validation
References
- advisoryhttps://documentation.solarwinds.com/en/success_center/servu/content/release_notes/servu_15-3_release_notes.htm
- advisoryhttps://thehackernews.com/2022/01/microsoft-hackers-exploiting-new.html
- advisoryhttps://www.microsoft.com/security/blog/2021/12/11/guidance-for-preventing-detecting-and-hunting-for-cve-2021-44228-log4j-2-exploitation/#CVE-2021-35247
- advisoryhttps://www.securityweek.com/log4shell-tools-and-resources-defenders-continuously-updated
- advisoryhttps://www.securityweek.com/microsoft-says-solarwinds-serv-u-zero-day-exploited-chinese-group
FAQ
Common Questions.
Serv-U web login screen to LDAP authentication was allowing characters that were not sufficiently sanitized.
Affected: Serv-U (Solarwinds) versions >= 15.2.5 and previous versions. The full list is in the CVE brief.
It is exploited in the wild, listed in CISA KEV, Industry KEV feed, CIRCL KEV, ENISA EUVD since Jan 19, 2022.
Yes. It was added on Jan 21, 2022 with a federal remediation due date of Feb 4, 2022.
Public exploit code is available.
Fixed versions are available, including Serv-U 15.3.
Brandefense priority: patch immediately, because it is listed as exploited in the wild.
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