NVD / CVE Program· CNA SolarWinds

CVE-2021-35247: Improper Input Validation Vulnerability in Serv-U

Noroxi assessment

Priority: This week (action score 60/100)

CISA has confirmed exploitation in the wild (Jan 21, 2022). Remediation deadline for US federal agencies: Feb 4, 2022.
A ready-made attack tool exists and the flaw can be exploited over the network without an account, so priority is at least “This week”.
Probability of exploitation in the next 30 days: 3.6% (FIRST EPSS); higher than 89.6% of all records.
Anyone who can reach it over the internet can trigger it. No account or password is required. No user action is required. No special conditions are required; it is repeatable.
According to the record, no fixed version is available yet.
Mentioned 2 times in Turkish national cyber security advisories (siberguvenlik.gov.tr).

Don’t wait for the next maintenance window. Until a fix is released, restrict access to the affected component and follow the vendor's advisory.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · CISA KEV · FIRST EPSS

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.

MediumCVSS 5.3 · v3.1KEVWeaponized No fix recorded

Pre-auth

BDU:2022-00742

Published: Jan 10, 2022
Updated: Jun 16, 2026
EPSS: 3.6% · 89th percentile
CWE: CWE-20

Report tools

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Action score

This week

Don’t wait for the next maintenance window.

CVSS: 21 / 40 · 5.3 / 10
CISA KEV: 30 / 30 · Listed
EPSS: 1 / 30 · 3.6%
Ready-made attack tool: 8 / 60 · floor: at least 60

CISA SSVC decision

Exploitation: active
Automatable: no
Technical impact: partial

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD: 5.3
CNA · SolarWinds: 4.3; 1.0 point gap

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

Actively exploited in the wild

CISA added this to its Known Exploited Vulnerabilities catalog on Jan 21, 2022. That signals real attacks, not theory.

Remediation deadline for US federal agencies: Feb 4, 2022.

Get told when this record changes

In CISA KEV: exploitation in the wild confirmed
Weaponized exploit exists
No fixed version yet

If any of these changes, we'll tell you in the daily email digest.

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

Vendor	Product	CPE
solarwinds	serv-u	cpe:2.3:a:solarwinds:serv-u

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

solarwinds serv-ubefore 15.3

Versions reported by the vendor

Affected version ranges reported by the assigning authority (SolarWinds). Independent of NVD's CPE analysis and usually ahead of it.

SolarWinds Serv-U
- 15.2.5 and previous versions and later · before 15.3affected

Same product

solarwinds: all records

Other highest-scoring records for the same primary product.

CVE-2021-35211Serv-U Remote Memory Escape VulnerabilityKEV
97Now
CVE-2024-28995SolarWinds Serv-U L Directory Transversal VulnerabilityKEV
90Now
CVE-2026-28318SolarWinds Serv-U Unauthenticated Denial of Service VulnerabilityKEV
73This week

Published before and after this one in the same product

← EarlierCVE-2021-35242Dec 6, 2021 · A valid CSRF token is present in response to an invalid request
35Monitor
← EarlierCVE-2021-35245Dec 6, 2021 · Broken Access Control Vulnerability for SolarWinds Serv-U
27Monitor
Later →CVE-2021-35250Apr 25, 2022 · Directory Transversal Vulnerability in Serv-U 15.3
34Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

No fix version is recorded for this entry. Check the references for vendor advisories.

Exploit status

Weaponized

A ready exploit tool or active in-the-wild use is known for this vulnerability. This should be your top priority.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

PublishedJan 10, 2022
CISA KEVJan 21, 2022+11 d
TodayNov 6, 2026+1761 d

No history yet (it accumulates with the daily EPSS job).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

No commit or PR link among the references.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

Jonathan Bar OrMicrosoft (@yo_yo_yo_jbo) for reporting this vulnerability

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

No nightly-computed relations.

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

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Bug bounty scope