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.
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.
References
gavinbarron Remediation developer
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.KiotaandMicrosoft.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.
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.
References