GHSA-3HRF-2GC2-MX32
Vulnerability from github – Published: 2026-07-24 15:30 – Updated: 2026-08-17 14:52
VLAI
Summary
Microsoft Kiota: XML Doc-Comment Newline Breakout Code Injection
Details
Summary
Kiota versions prior to 1.32.3 and 1.29.1 are affected by a code-generation injection vulnerability in the C# XML documentation-comment sink (the description, externalDocs label, and externalDocs link fields emitted as /// … comments).
When text from an OpenAPI description is written into single-line XML doc comments without stripping newline and Unicode line-terminator characters, an attacker can break out of the /// comment line and inject additional code into generated C# clients.
Impact and Preconditions
This issue is only practically exploitable when:
- the OpenAPI description used for generation is from an untrusted source, or
- a normally trusted OpenAPI description has been compromised/tampered with.
The injected code is compiled (and may execute) when the developer or CI builds the generated client. If you only generate from trusted, integrity-protected API descriptions, risk is significantly reduced.
Affected Versions
- Affected: all versions < 1.29.1, >= 1.30.0, < 1.32.3
- Fixed: 1.29.1, 1.32.3, and later
Illustrative Exploit Example
Example OpenAPI fragment (malicious description)
openapi: 3.0.1
info:
title: Exploit Demo
version: 1.0.0
description: |-
Legitimate summary text
public static class Pwned { static Pwned() { System.Diagnostics.Process.Start("calc.exe"); } }
The newline inside description (also exploitable via \r, U+0085, U+2028, U+2029) terminates the doc-comment line.
Example generated C# snippet before fix (illustrative)
/// Legitimate summary text
public static class Pwned { static Pwned() { System.Diagnostics.Process.Start("calc.exe"); } }
The injected payload escapes the intended /// comment context and introduces attacker-controlled statements in generated code.
Note: this exploit is not limited to the
descriptionfield, but may also impact theexternalDocslabel and link text and other doc-comment-derived locations.
Remediation
- Upgrade Kiota to 1.32.3 or later.
- Regenerate/refresh existing generated clients as a precaution:
Refreshing generated clients ensures previously generated vulnerable code is replaced with hardened output. The fix (PR microsoft/kiota#7831) strips \r, \n, \u0085, \u2028, \u2029 (and normalizes tabs) from description, label, and link text before emitting doc comments.
Severity
{
"affected": [
{
"package": {
"ecosystem": "NuGet",
"name": "Microsoft.OpenApi.Kiota"
},
"ranges": [
{
"events": [
{
"introduced": "1.30.0"
},
{
"fixed": "1.32.3"
}
],
"type": "ECOSYSTEM"
}
]
},
{
"package": {
"ecosystem": "NuGet",
"name": "Microsoft.OpenApi.Kiota.Builder"
},
"ranges": [
{
"events": [
{
"introduced": "1.30.0"
},
{
"fixed": "1.32.3"
}
],
"type": "ECOSYSTEM"
}
]
},
{
"package": {
"ecosystem": "NuGet",
"name": "Microsoft.OpenApi.Kiota"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"fixed": "1.29.1"
}
],
"type": "ECOSYSTEM"
}
]
},
{
"package": {
"ecosystem": "NuGet",
"name": "Microsoft.OpenApi.Kiota.Builder"
},
"ranges": [
{
"events": [
{
"introduced": "0"
},
{
"fixed": "1.29.1"
}
],
"type": "ECOSYSTEM"
}
]
}
],
"aliases": [
"CVE-2026-59860"
],
"database_specific": {
"cwe_ids": [
"CWE-94"
],
"github_reviewed": true,
"github_reviewed_at": "2026-07-24T15:30:47Z",
"nvd_published_at": "2026-07-16T15:16:35Z",
"severity": "HIGH"
},
"details": "### Summary\n\nKiota versions **prior to 1.32.3 and 1.29.1** are affected by a code-generation injection vulnerability in the C# XML documentation-comment sink (the `description`, `externalDocs` label, and `externalDocs` link fields emitted as `/// \u2026` comments).\n\nWhen text from an OpenAPI description is written into single-line XML doc comments without stripping newline and Unicode line-terminator characters, an attacker can break out of the `///` comment line and inject additional code into generated C# clients.\n\n## Impact and Preconditions\n\nThis issue is only practically exploitable when:\n\n1. the OpenAPI description used for generation is from an **untrusted source**, or\n2. a normally trusted OpenAPI description has been **compromised/tampered with**.\n\nThe injected code is compiled (and may execute) when the developer or CI **builds** the generated client. If you only generate from trusted, integrity-protected API descriptions, risk is significantly reduced.\n\n## Affected Versions\n\n- **Affected:** all versions **\u003c 1.29.1**, **\u003e= 1.30.0, \u003c 1.32.3**\n- **Fixed: 1.29.1, 1.32.3,** and later\n\n## Illustrative Exploit Example\n\n### Example OpenAPI fragment (malicious description)\n\n```yaml\nopenapi: 3.0.1\ninfo:\n title: Exploit Demo\n version: 1.0.0\n description: |-\n Legitimate summary text\n public static class Pwned { static Pwned() { System.Diagnostics.Process.Start(\"calc.exe\"); } }\n```\n\nThe newline inside `description` (also exploitable via `\\r`, U+0085, U+2028, U+2029) terminates the doc-comment line.\n\n### Example generated C# snippet before fix (illustrative)\n\n```csharp\n/// Legitimate summary text\npublic static class Pwned { static Pwned() { System.Diagnostics.Process.Start(\"calc.exe\"); } }\n```\n\nThe injected payload escapes the intended `///` comment context and introduces attacker-controlled statements in generated code.\n\n\u003e Note: this exploit is not limited to the `description` field, but may also impact the `externalDocs` label and link text and other doc-comment-derived locations.\n\n## Remediation\n\n1. Upgrade Kiota to **1.32.3 or later**.\n2. Regenerate/refresh existing generated clients as a precaution:\n\nRefreshing generated clients ensures previously generated vulnerable code is replaced with hardened output. The fix (PR microsoft/kiota#7831) strips `\\r`, `\\n`, `\\u0085`, `\\u2028`, `\\u2029` (and normalizes tabs) from description, label, and link text before emitting doc comments.",
"id": "GHSA-3hrf-2gc2-mx32",
"modified": "2026-08-17T14:52:01Z",
"published": "2026-07-24T15:30:47Z",
"references": [
{
"type": "WEB",
"url": "https://github.com/microsoft/kiota/security/advisories/GHSA-3hrf-2gc2-mx32"
},
{
"type": "ADVISORY",
"url": "https://nvd.nist.gov/vuln/detail/CVE-2026-59860"
},
{
"type": "WEB",
"url": "https://github.com/microsoft/kiota/pull/7831"
},
{
"type": "WEB",
"url": "https://github.com/microsoft/kiota/commit/ebb632db90aa8e3c20949337d9faa2720d64ca44"
},
{
"type": "PACKAGE",
"url": "https://github.com/microsoft/kiota"
},
{
"type": "WEB",
"url": "https://github.com/microsoft/kiota/releases/tag/v1.32.3"
}
],
"schema_version": "1.4.0",
"severity": [
{
"score": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N",
"type": "CVSS_V4"
}
],
"summary": "Microsoft Kiota: XML Doc-Comment Newline Breakout Code Injection"
}
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Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
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The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the
vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base
model, served locally by ML-Gateway.
They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
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