CVE-2026-105796: 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.
Other sources
Kiota is an OpenAPI based HTTP Client code generator. From 0.5.0 until 1.35.0, Kiota's Java and PHP documentation-comment sanitizers delete block-comment terminators rather than neutralizing them, allowing overlapping characters to reform a terminator and place attacker-controlled OpenAPI text outside a generated documentation comment. The Java sanitizer also removes non-ASCII characters after deleting terminators, which can create a new terminator during normalization. Exploitation requires a developer or build pipeline to generate source from the malicious description and then compile and load the Java output or load the PHP output, after which injected code executes in the consuming application or build environment context. The version range is based on the Java defect and does not assert that PHP generation existed in every affected release. This issue is fixed in version 1.35.0.
— MITRE
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
nuget/Microsoft.OpenApi.Kiota.Builderto a version that resolves this vulnerability.Fixed in 1.35.0 - Upgrade
Upgrade
nuget/Microsoft.OpenApi.Kiotato a version that resolves this vulnerability.Fixed in 1.35.0 - Upgrade
Upgrade
Kiotato a version that resolves this vulnerability.Fixed in 1.35.0 - Compensating control
Until upgrading, generate clients only from trusted, integrity-protected OpenAPI descriptions.
- Compensating control
Restrict the privileges and secrets available to generation and build environments.
- Compensating control
Review generated Java and PHP source before compiling, loading, or deploying it.
- Operational
After upgrading, regenerate affected clients.
Event History
Frequently Asked Questions
Who is exposed to this issue?
Teams that generate Java or PHP clients from OpenAPI descriptions are exposed when those descriptions can be attacker-controlled or come from an untrusted source. The risk materializes in the application or build environment that compiles and loads the generated Java output or loads the generated PHP output.
What must an attacker provide or cause for exploitation?
An attacker needs a malicious OpenAPI description whose text is processed into generated documentation comments. A developer or build pipeline must then generate source from that description and compile and load the Java output, or load the PHP output.
Which versions should be remediated?
Kiota versions from 0.5.0 through 1.35.0 are identified as affected, and version 1.35.0 fixes the issue. The stated range is based on the Java defect and does not establish that PHP generation was present in every release in that range.
What should be done if generated clients cannot immediately be updated?
Do not generate or load clients from untrusted OpenAPI descriptions until the generator can be updated to the fixed version. Treat generated Java compilation/loading and PHP loading as execution of code in the consuming application or build environment context.