Code Injection in Microsoft.OpenAPI.Kiota (CVE-2026-59861)
Summary
Code injection in Microsoft.OpenAPI.Kiota (CVE-2026-59861). Risk of unauthorized operations or information disclosure. Mitigation: upgrade to 1.29.1 or later.
Original description
The description as published by the source.
Code Generation Literal Injection in Kiota Ruby Generator Leads to Arbitrary Code Execution
Impact
The Kiota Ruby code generator is vulnerable to a code generation literal injection attack. The generator embeds string values from OpenAPI default fields and property names directly into Ruby double-quoted string literals without properly escaping the # character. Since Ruby evaluates string interpolation expressions like #{expr}, #$var, and #@var within double-quoted strings at runtime, an attacker who controls an OpenAPI specification file can inject arbitrary Ruby code into generated model classes.
Who is impacted
Developers using Kiota to generate Ruby API clients from external or untrusted OpenAPI specifications
Teams with CI/CD pipelines configured to automatically regenerate client code from remote specs
Applications that deploy generated Ruby code to production servers
Vulnerability details
Affected component: CodeMethodWriter.cs
Root cause: The shared SanitizeForQuotedLiteral() function in Writers/StringExtensions.cs does not escape the # character
Attack vectors
OpenAPI default fields in schema properties
Property wire-name hash keys in deserializer/serializer methods
Any schema-derived string embedded in Ruby double-quoted literals
Severity: Critical when generated code reaches production; High for CI/CD environments with access to production secrets; Medium for public third-party specs; Low for developer-controlled specs.
Patches
Source: NIST National Vulnerability Database NVD GitHub Advisory
Auto-generated summary
Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.
A vulnerability tracked as CVE-2026-59861 has been found in Microsoft.OpenAPI.Kiota.
Risk of unauthorized operations or information disclosure. CVSS score: 7.5/10.
What to do: upgrade Microsoft.OpenAPI.Kiota to 1.29.1 or later.
If unsure, ask your IT team or search "Microsoft.OpenAPI.Kiota CVE-2026-59861" on the vendor's site.
CVE-2026-59861 (Microsoft.OpenAPI.Kiota) — CWE-94 / CVSS v3 7.5
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Patched: 1.29.1 — apply immediately
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.
Arbitrary code execution (CWE-94) exists in Microsoft.OpenAPI.Kiota.
Check the vendor advisory for the affected versions of Microsoft.OpenAPI.Kiota.
Severity: High (CVSS 7.5/10). Risk of unauthorized operations or information disclosure.
Update to 1.29.1.
Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.
Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Run grep -r 'Microsoft.OpenAPI.Kiota' . against your dependency files (package-lock.json, requirements.txt, go.sum) to find affected services.
Response actions
Concrete steps and command examples for SOC/SRE teams to execute in order
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1Identify exposure identify
grep -r 'Microsoft.OpenAPI.Kiota' . | grep -v node_modulesリポジトリと本番環境の依存ファイル (package-lock.json / requirements.txt / go.sum / Gemfile.lock 等) で
Microsoft.OpenAPI.Kiotaを grep し、稼働しているサービス・バージョンを把握する。 -
2Apply patch patch
Upgrade Microsoft.OpenAPI.Kiota to 1.29.1ステージング環境で 1.29.1 に上げて回帰テスト → 本番反映。回帰テストはアプリの主要ハッピーパスを含めること。
-
3Post-deployment verification verify
Confirm patched version is live in productionパッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。
Affected packages
References
- advisory nvd.nist.gov
- package github.com
- web github.com
- web github.com
- web github.com
- web github.com
- web github.com