How severe is CVE-2021-41355?

CVE-2021-41355 has a CVSS score of 5.7/10, rated MEDIUM. Review your exposure and patch according to your risk tolerance.

Which packages are affected by CVE-2021-41355?

CVE-2021-41355 affects the following packages: System.DirectoryServices.Protocols (NuGet). Ecosystems affected: NuGet.

How do I fix CVE-2021-41355?

Update System.DirectoryServices.Protocols to 5.0.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-41355 is resolved across your whole dependency graph.

How do I detect CVE-2021-41355 in my NuGet dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for System.DirectoryServices.Protocols, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2021-41355 if there is no patch (or I can't update yet)?

Assume what was exposed is already known: rotate any credential, token or key that the affected component could return, restrict the endpoint to callers that genuinely need it, and strip sensitive fields from responses and error output at the boundary rather than relying on the client not to read them.

Is CVE-2021-41355 actively exploited in the wild?

No public exploit code has been indexed for CVE-2021-41355 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2021-41355?

CVE-2021-41355 has an EPSS (Exploit Prediction Scoring System) score of 20.3%, placing it in the 97th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score warrants monitoring and prompt remediation.

When was CVE-2021-41355 published, and has it been updated?

CVE-2021-41355 was published on October 13, 2021 and was last updated on September 22, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

.NET

.NET NuGet

Not in CISA KEV

MEDIUM severity

CVE-2021-41355 — System.DirectoryServices.…

MEDIUM

CVE-2021-41355 is a medium-severity (CVSS 5.7) vulnerability in System.DirectoryServices.Protocols. EPSS puts its 30-day exploitation probability at 20.3% (97th percentile). A fix is available for System.DirectoryServices.Protocols — see the affected versions and patch details below.

Credential Disclosure in System.DirectoryServices.Protocols

Also known asBIT-dotnet-2021-41355BIT-dotnet-sdk-2021-41355BIT-powershell-2021-41355GHSA-9cxh-gqpx-qc5m

Published

Oct 13, 2021

Updated

Sep 22, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Oct 9, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗

20.3%probability of exploitation in next 30 days

Moderate Risk0.00%

Lower risk than most CVEs97th percentile — riskier than 97% of all scored CVEsHighest risk

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

CVE-2021-41355 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.

Where this sits among everything scored

Of 385,738 CVEs with a current EPSS score, this one falls in the 10–50% band (highlighted). Counts from FIRST.org, log-scaled.

Real-World Exposure

1 pkg affected

.NETSystem.DirectoryServices.Protocols

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects NuGet packages — download data is not available via public APIs for these ecosystems.

Description

A Information Disclosure vulnerability exists in .NET where System.DirectoryServices.Protocols.LdapConnection may send credentials in plain text on Linux.

Patches

Any .NET application that uses System.DirectoryServices.Protocols with a vulnerable version listed below on system based on Linux.

Package name	Vulnerable versions	Secure versions
System.DirectoryServices.Protocols	5.0.0	5.0.1

Other Details

Announcement for this issue can be found at dotnet/announcements#202
An Issue for this can be found at https://github.com/dotnet/runtime/issues/60301
MSRC details for this can be found at https://msrc.microsoft.com/update-guide/en-US/vulnerability/CVE-2021-41355

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
.NETNuGet	`System.DirectoryServices.Protocols`	all versions	5.0.1`dotnet add package System.DirectoryServices.Protocols --version 5.0.1`

Affected Products

3 products · 3 configurations

Application

.netmicrosoft

1 version

5.0

Application

powershellmicrosoft

≥ 7.1 && < 7.1.5

range

Application

visual studio 2019microsoft

≥ 16.0 && ≤ 16.11

range

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for System.DirectoryServices.Protocols, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update System.DirectoryServices.Protocols to 5.0.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-41355 is resolved across your whole dependency graph.
Workarounds
Assume what was exposed is already known: rotate any credential, token or key that the affected component could return, restrict the endpoint to callers that genuinely need it, and strip sensitive fields from responses and error output at the boundary rather than relying on the client not to read them.

Fixing This On Your OS

If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.

Red HatImportant

Product	Fixed in	Advisory
.NET Core on Red Hat Enterprise Linux	`rh-dotnet50-dotnet-0:5.0.208-1.el7_9`	RHSA-2021:3818
Red Hat Enterprise Linux 8	`dotnet5.0-0:5.0.208-1.el8_4`	RHSA-2021:3819

Frequently Asked Questions

Microsoft is releasing this security advisory to provide information about a vulnerability in .NET. This advisory also provides guidance on what developers can do to update their applications to remove this vulnerability. A Information Disclosure vulnerability exists in .NET where System.DirectoryServices.Protocols.LdapConnection may send credentials in plain text on Linux. ### Patches Any .NET application that uses `System.DirectoryServices.Protocols` with a vulnerable version listed below on system based on Linux. Package name | Vulnerable versions | Secure versions ------------ | -------

O3 Security · Impact-Aware SCA

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CVSS Score

5.7/10CVSS v3 base

Vector breakdown

Attack Vector

Adjacent

Attack Complexity

Low

Privileges Required

None

User Interaction

Required

Scope

Unchanged

Confidentiality

High

Integrity

None

Availability

None

Raw vector

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

Weaponization

No known public exploit tooling found.

OpenSSF Scorecard

Package health score

runtime

6.5/10

Maintained10/10

Code-Review10/10

Branch-Protection8/10

Assessed Oct 5, 2026

Timeline

Disclosed

Oct 13, 2021

Last updated

Sep 22, 2026

Identifiers

CVE-2021-41355

GHSA-9cxh-gqpx-qc5m

BIT-dotnet-2021-41355

BIT-dotnet-sdk-2021-41355

BIT-powershell-2021-41355

References

Advisoryoracle.com Advisorynvd.nist.gov Fixportal.msrc.microsoft.com Webgithub.com Webgithub.com Webmsrc.microsoft.com Packagegithub.com

Provenance

Sources

OSV.devNVDFIRST.org (EPSS)

Last verifiedSep 22, 2026

CVE-2021-41355 — System.DirectoryServices.…

EPSS Exploitation Probability

How urgent is this, really

Where this sits among everything scored

Real-World Exposure

Description

Patches

Other Details

Affected Packages

Affected Products

Detection & mitigation playbook

Detect

Fix

Workarounds

Fixing This On Your OS

Frequently Asked Questions

Is CVE-2021-41355 in your dependencies?