CVE-2026-44503 Kiota abstractions RedirectHandler leaks Cookie/Proxy-Authorization headers on cross-host redirect
The Kiota HTTP client libraries leak sensitive Cookie and Proxy-Authorization headers to external hosts during cross-host redirects, exposing user credentials.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- Available
What is CVE-2026-44503?
CVE-2026-44503 is a high-severity vulnerability in Microsoft.Kiota.Abstractions, published on 14 May 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Official description
The RedirectHandler middleware in microsoft/kiota-java (com.microsoft.kiota:microsoft-kiota-http-okHttp v1.9.0) and other Kiota libraries fails to strip sensitive HTTP headers when following 3xx redirects to a different host or scheme. Only the Authorization header is removed; Cookie, Proxy-Authorization, and all custom headers are forwarded to the redirect target.
Weakness: CWE-601
Which versions are affected by CVE-2026-44503?
12 open source packages ship an affected version, including Microsoft.Kiota.Abstractions, github.com/microsoft/kiota-http-go and com.microsoft.kiota:microsoft-kiota-abstractions.
| Package | Affected | Fixed in |
|---|---|---|
Microsoft.Kiota.Abstractions NuGet | All versions | 1.22.0 |
Microsoft.Kiota.Abstractions NuGet | All versions | 1.22.0 |
github.com/microsoft/kiota-http-go Go | All versions | 1.5.5 |
github.com/microsoft/kiota-http-go Go | All versions | 1.5.5 |
github.com/microsoft/kiota-http-go Go | All versions | 1.5.5 |
com.microsoft.kiota:microsoft-kiota-abstractions Maven | All versions | 1.9.1 |
6 more packages
com.microsoft.kiota:microsoft-kiota-abstractions Maven | All versions | 1.9.1 |
microsoft-kiota-http PyPI | All versions | 1.9.9 |
microsoft-kiota-http PyPI | All versions | 1.9.9 |
microsoft-kiota-http PyPI | All versions | 1.9.9 |
kiota-typescript npm | All versions | 1.0.0-preview.100 |
kiota-typescript npm | All versions | 1.0.0-preview.100 |
How do I fix CVE-2026-44503?
Upgrade Microsoft.Kiota.Abstractions to 1.22.0 or later.
Is CVE-2026-44503 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-44503 exists.
Sources
Also known as CLEANSTART-2026-DB48135, CLEANSTART-2026-VZ99865, ECHO-0e0d-c481-2581, GHSA-7j59-v9qr-6fq9, GO-2026-5224, MINI-56g5-7v32-5c2q and 14 more.