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

### 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 Java delimiter neutralization after non-ASCII normalization. - Fix: https://github.com/microsoft/kiota/pull/8017 - Fixed release: https://github.com/microsoft/kiota/releases/tag/v1.35.0 ### Workarounds Until upgrading, generate clients only from trusted, integrity-protected OpenAPI descriptions. Review generated Java and PHP source before compiling, loading, or deploying it. Restrict the privileges and secrets available to generation and build environments. ### Related advisories This is distinct from PHP double-quoted string interpolation (GHSA-jqwh-526h-c92j) and C# XML documentation newline breakout (GHSA-3hrf-2gc2-mx32). Those fixes do not address Java/PHP block-comment delimiter reformation.

Source published

6 Oct 2026 15:36:00 UTC

Source modified

6 Oct 2026 15:46:48 UTC

Observed here

23 Oct 2026 16:01:25 UTC

Source terms

GitHub Advisory Database · CC-BY-4.0

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This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: osv · GitHub Advisory Database · CC-BY-4.0. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS_V3 · CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

Publisher rating · HIGH