CVE-2026-59866: Kiota is an OpenAPI based HTTP Client code generator

Q: How do I fix CVE-2026-59866?

No fixed release is listed yet. Watch the vendor advisory and apply any mitigation shown on this page.

Q: Is CVE-2026-59866 being exploited?

CVE-2026-59866 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2026-59866 affect?

CVE-2026-59866 affects affected software. Severity is critical (CVSS 9.3). Kiota is an OpenAPI based HTTP Client code generator. Prior to 1.29.1 and 1.32.5, Kiota emitted x-ms-kiota-info clientClassName and clientNamespaceName values without identifier or path sanitization as both generated client class or namespa

Q: How urgent is CVE-2026-59866?

Priority 59/100. Critical severity; CISA SSVC: automatable with total technical impact; Remotely exploitable, no login, no user action

This month

CRITICAL 9.3REMOTE

CVE-2026-59866 is a critical-severity flaw (CVSS 9.3) affecting affected software. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Kiota is an OpenAPI based HTTP Client code generator. Prior to 1.29.1 and 1.32.5, Kiota emitted x-ms-kiota-info clientClassName and clientNamespaceName values without identifier or path sanitization as both generated client class or namespace names and generated output path components when `kiota generate` ran without -c/--class-name, allowing an attacker-controlled or compromised OpenAPI description to write generated source outside the -o outpu

Why this priority

Critical severity
CISA SSVC: automatable with total technical impact
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	9.3 (Critical)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	1.4% (top 27%)
CISA exploited list	No
Weakness	CWE-22, CWE-94
Published	2026-07-16
Last modified	2026-10-24

Publisher (CNA): GitHub, Inc.

Last updated 2026-10-24 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Timeline

2026-07-16 16:19 UTCPublished CVE record published
2026-10-24 20:10 UTCUpdated Record last modified

Exact fixes by distribution

NuGet (.NET) · Microsoft.OpenApi.Kiota · FIXED · 1.32.5 · vulnerable: >= 1.30.0, < 1.32.5 · source

dotnet add package Microsoft.OpenApi.Kiota --version 1.32.5

NuGet (.NET) · Microsoft.OpenApi.Kiota.Builder · FIXED · 1.32.5 · vulnerable: >= 1.30.0, < 1.32.5 · source

dotnet add package Microsoft.OpenApi.Kiota.Builder --version 1.32.5

Fedora 46 · conda · FIXED · 26.9.4-2.fc46 · FEDORA-2026-09931756f1 · source

sudo dnf upgrade --advisory=FEDORA-2026-09931756f1

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-59866?

No fixed release is listed yet. Watch the vendor advisory and apply any mitigation shown on this page.

Is CVE-2026-59866 being exploited?

CVE-2026-59866 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-59866 affect?

CVE-2026-59866 affects affected software. Severity is critical (CVSS 9.3). Kiota is an OpenAPI based HTTP Client code generator. Prior to 1.29.1 and 1.32.5, Kiota emitted x-ms-kiota-info clientClassName and clientNamespaceName values without identifier or path sanitization as both generated client class or namespa

How urgent is CVE-2026-59866?

Priority 59/100. Critical severity; CISA SSVC: automatable with total technical impact; Remotely exploitable, no login, no user action

References

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