Code Injection in Microsoft.OpenApi.Kiota (CVE-2026-105796)
Summary
Code injection in Microsoft.OpenApi.Kiota (CVE-2026-105796). Successful exploitation can lead to full system takeover. Exploitable via Microsoft.OpenApi.Kiota. Mitigation: upgrade to 1.35.0 or later.
Original description
The description as published by the source.
Impact
An attacker who controls or tampers with an OpenAPI description can cause Kiota to emit attacker-controlled Java or PHP source outside a generated documentation comment. The affected sanitizers remove comment terminators rather than neutralizing them, allowing a terminator to reform from overlapping characters or from subsequent normalization. The Java sanitizer also removes non-ASCII characters after removing terminators, which can create a new terminator.
Exploitation requires a developer or build pipeline to generate a client from the malicious description and subsequently compile and load the Java output, or load the PHP output. Code executes in the consuming application's or build environment's security context, not merely because Kiota reads the description.
Affected versions
The affected NuGet packages are Microsoft.OpenApi.Kiota and Microsoft.OpenApi.Kiota.Builder. The Java normalization-order defect was introduced in version 0.5.0 and remains present through version 1.34.1, including the separate 1.29.1 security-backport release. The PHP delimiter-reformation variant is also present in version 1.34.1 and 1.29.1. Version 1.35.0 fixes both variants.
The package version range below reflects the Java defect; it does not assert that PHP generation existed in every version in that range.
Patches
Upgrade to Kiota 1.35.0 or later and regenerate affected clients. The fix neutralizes block-comment delimiters instead of deleting them, and performs…
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-2026-105796 has been found in Microsoft.OpenApi.Kiota.
Attackers can target a specific entry point like Microsoft.OpenApi.Kiota over the network to misuse the product.
Successful exploitation can lead to full system takeover. CVSS score: 8.8/10.
What to do: upgrade Microsoft.OpenApi.Kiota to 1.35.0 or later.
If unsure, ask your IT team or search "Microsoft.OpenApi.Kiota CVE-2026-105796" on the vendor's site.
CVE-2026-105796 (Microsoft.OpenApi.Kiota) — CWE-94 / CVSS v3 8.8
Attack vector: remote (network-reachable) / unauthenticated
Attack surface: Microsoft.OpenApi.Kiota / Microsoft.OpenApi.Kiota.Builder
Patched: 1.35.0 — apply immediately
Workaround: Until upgrading, generate clients only from trusted, integrity-protected OpenAPI descriptions.
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. Attackers reach the vulnerable code path via Microsoft.OpenApi.Kiota without authentication.
Check the vendor advisory for the affected versions of Microsoft.OpenApi.Kiota. Attack surface: Microsoft.OpenApi.Kiota / Microsoft.OpenApi.Kiota.Builder.
Severity: High (CVSS 8.8/10). Successful exploitation can lead to full system takeover.
Update to 1.35.0.
Workaround: Until upgrading, generate clients only from trusted, integrity-protected OpenAPI descriptions.
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 temporary workaround mitigate
Until upgrading, generate clients only from trusted, integrity-protected OpenAPI descriptions.パッチが適用されるまでの応急処置として、Until upgrading, generate clients only from trusted, integrity-protected OpenAPI descriptions. を実施。回避策の副作用 (機能低下) を確認した上で。
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3Apply patch patch
Upgrade Microsoft.OpenApi.Kiota to 1.35.0ステージング環境で 1.35.0 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。
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4Post-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