Remote code execution via undisclosed text encoding flaw
Published Feb 25, 2021 · Updated May 28, 2026
Remote code execution in Microsoft's System.Text.Encodings.Web package allows remote attackers to execute arbitrary code via unspecified vectors. Microsoft attributes the flaw to text encoding but has not disclosed the affected API or the incorrect operation performed on untrusted input. Network access without authentication is sufficient, while successful exploitation depends on unspecified conditions reflected by the vendor's high attack-complexity assessment.
Summary
What happened
Remote code execution in Microsoft's System.Text.Encodings.Web package allows remote attackers to execute arbitrary code via unspecified vectors. Microsoft attributes the flaw to text encoding but has not disclosed the affected API or the incorrect operation performed on untrusted input. Network access without authentication is sufficient, while successful exploitation depends on unspecified conditions reflected by the vendor's high attack-complexity assessment.
The record
- CVE
- CVE-2021-26701
- Published
- Feb 25, 2021
- Updated
- May 28, 2026
- Vendor
- Microsoft
- Product
- .NET Core 2.1
- Classifications
- Unavailable
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Feb 25, 2021CVE publishedPublication date reported by the CVE source.
- May 28, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
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- Affected versionversion=2.1 <publication
What conditions does exploitation require?
What is affected?
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.
Weakness, pattern, technique
No sourced classifications are available.
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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