Kiota: Code injection through doc-comment delimiter reformation in Kiota Java and PHP generators

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

8.8 · CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

EPSS

• CVE-2026-105796: 0.90% estimated exploitation activity in the next 30 days; percentile 59.60 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

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…

Published by the source

6 Oct 2026, 15:36 UTC

Last modified by the source

6 Oct 2026, 15:46 UTC

Source last checked

26 Oct 2026, 17:05 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-rm89-rhwj-9j92

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-rm89-rhwj-9j92

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# Patch Next advisory brief: CVE-2026-105796

Advisory: Kiota: Code injection through doc-comment delimiter reformation in Kiota Java and PHP generators
IDs: CVE-2026-105796, GHSA-rm89-rhwj-9j92
Record: https://patchnext.com/advisories/cve-2026-105796 (revision 2, source checked 26 Oct 2026, 17:05 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 8.8)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: microsoft.openapi.kiota 1.35.0; microsoft.openapi.kiota.builder 1.35.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- NuGet microsoft.openapi.kiota: affected >= 0.5.0, < 1.35.0; fixed in 1.35.0
- NuGet microsoft.openapi.kiota.builder: affected >= 0.5.0, < 1.35.0; fixed in 1.35.0

## Suggested inspection (read-only)
- NuGet microsoft.openapi.kiota: check the installed version with your package manager.
- NuGet microsoft.openapi.kiota.builder: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on microsoft.openapi.kiota, microsoft.openapi.kiota.builder.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-rm89-rhwj-9j92 (OSV record GHSA-rm89-rhwj-9j92 lists affected ranges: NuGet microsoft.openapi.kiota >=0.5.0 =0.5.0 <1.35.0 (fixed))
- Verified: https://github.com/advisories/GHSA-rm89-rhwj-9j92 (GitHub-reviewed advisory GHSA-rm89-rhwj-9j92 lists affected ranges: NuGet microsoft.openapi.kiota >=0.5.0 =0.5.0 <1.35.0)

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