Service interruption via malformed Base64Url decoding
Published Mar 10, 2026 · Updated Mar 10, 2026
Out-of-bounds read in Microsoft .NET and Microsoft.Bcl.Memory allows remote attackers to interrupt services via malformed Base64Url input. The Base64Url decoder fails to validate an array index before reading malformed encoded data, causing a read beyond the intended bounds. No authentication or user interaction is required, but an application must pass attacker-controlled Base64Url data to the affected decoder; no data disclosure or modification is documented.
Summary
What happened
Out-of-bounds read in Microsoft .NET and Microsoft.Bcl.Memory allows remote attackers to interrupt services via malformed Base64Url input. The Base64Url decoder fails to validate an array index before reading malformed encoded data, causing a read beyond the intended bounds. No authentication or user interaction is required, but an application must pass attacker-controlled Base64Url data to the affected decoder; no data disclosure or modification is documented.
The record
- CVE
- CVE-2026-26127
- Published
- Mar 10, 2026
- Updated
- Mar 10, 2026
- Vendor
- Microsoft
- Product
- Microsoft.Bcl.Memory
- Classifications
- CWE-125, CWE-129, T1499.004
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Mar 10, 2026CVE publishedPublication date reported by the CVE source.
- Mar 10, 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?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=10.0.0 <10.0.4
- Affected versionversion=9.0.0 <9.0.14
What conditions does exploitation require?
What is affected?
Published CVSS scores
CVSS describes severity. EPSS estimates exploitation probability.
Attacks
What attackers are doing with it
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Weakness, pattern, technique
Public exploit references
No public exploit references are available in this record.
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Technologies
Your stack
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Your stack
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