⚠ Reference material — not professional advice. Test in staging, back up first, verify against your specific version. Use your own judgment for your environment.
● High · CVSS 7

How to Fix CVE-2026-44503: Open Redirect in kiota-java

Other vulnerabilities in the same area that are worth patching alongside this one:

*By Sai Kiran Pandrala*

⚡ At a glance
SeverityCVSS 7 - High
Actively exploited?Not currently listed in CISA KEV
Affected< 1.9.1, < 1.22.0, < 1.5.5, < 1.0.0-preview.100, < 1.9.1, < 1.9.9
Fixed inSee vendor advisory
Type (CWE)CWE-601: URL Redirection to Untrusted Site ('Open Redirect')

What is CVE-2026-44503?

CVE-2026-44503 is an open-redirect flaw in kiota-java. The product forwards users to a URL taken from a parameter without validating the destination, which phishing campaigns use to abuse the product's trusted domain. Vendor 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.

Why this CVE matters

Open redirects on a trusted domain are routinely used by phishing kits to land victims on credential-harvesting pages while bouncing through a domain the victim trusts.

For deployments of kiota-java that have been exposed to the public internet during the disclosure window, the operating assumption should be that scanning has already happened. Even where exploitation has not been publicly observed, scanning for the vulnerable fingerprint is cheap and routine. Patching closes the door; log review and credential rotation close out the rest of the response.

Am I affected?

You are affected if your installation matches any of these version ranges:

Check your installed version against the list above. If you cannot determine the version, treat the system as affected and follow the upgrade path below.

On Windows, check the product's installed version via Settings - Apps - Installed apps, or run Get-Package from PowerShell to enumerate installed versions.

How to fix CVE-2026-44503

  1. Read the vendor advisory in full: https://github.com/microsoft/kiota-java/security/advisories/GHSA-7j59-v9qr-6fq9
  2. Upgrade kiota-java to the patched build listed in the vendor advisory.
  3. Back up the configuration (and database, where applicable) before upgrading.
  4. Apply the patch in a maintenance window. For HA pairs, upgrade the standby node first, fail over, then upgrade the former primary.
  5. Restart the affected service so the patched binary loads, then verify the new version (see verification section).

Update the maven / gradle dependency


# CVE-2026-44503 affects kiota-java < 1.9.1. Fixed in 1.9.1.
# Vendor advisory: https://github.com/microsoft/kiota-java/security/advisories/GHSA-7j59-v9qr-6fq9

# Maven: bump the dependency in pom.xml then re-resolve.
mvn versions:use-dep-version -Dincludes=kiota-java -DdepVersion=1.9.1 -DforceVersion=true
mvn clean install

# Gradle: bump in build.gradle then refresh.
./gradlew --refresh-dependencies build

# Restart the affected JVM service so the patched JAR loads.
sudo systemctl restart <service-name>

# Verify the runtime is on the patched build.
java -version


# Vendor advisory: https://github.com/microsoft/kiota-java/security/advisories/GHSA-7j59-v9qr-6fq9
# Restart the equivalent Windows service after upgrading the JAR.
Restart-Service -Name "<service-name>"
Get-Service -Name "<service-name>"

Verify the fix landed


# CVE-2026-44503 verification checklist.

# 1. Confirm the running version matches 1.9.1 (replace the version probe with
#    the platform-specific command shown above).

# 2. Re-scan the host with your vulnerability scanner (Nessus, Qualys, Tenable,
#    OpenVAS, Wazuh). The scanner must no longer flag CVE-2026-44503.

# 3. Inspect recent service and kernel logs for crash-loops or rollback events.
journalctl -u <service-name> --since "10 minutes ago"
dmesg --since "10 minutes ago"

# 4. Cross-check the running build against the vendor advisory:
#    https://github.com/microsoft/kiota-java/security/advisories/GHSA-7j59-v9qr-6fq9

If you cannot patch immediately

Block the redirect parameter at a reverse proxy, or strip it from inbound requests. Patch as the durable fix.

How to verify the fix worked

If your installation was internet-reachable during the disclosure window, treat log review as part of the remediation rather than an optional follow-up. Look for log entries that do not match your normal request patterns, especially repeated requests to the same uncommon endpoint, and any administrative changes you cannot tie back to a known operator.

Frequently asked questions

Is CVE-2026-44503 being exploited in the wild?

Public exploitation has not been confirmed by CISA at the time of writing. Treat the patch as time-sensitive anyway; reports often lag actual abuse.

Will a WAF or IDS rule fully mitigate CVE-2026-44503?

No. Network-layer filters can reduce noise and slow opportunistic scanners, but they will not stop a determined attacker. The vendor patch is the only durable fix.

How long should I plan for the upgrade?

Typical vendor-documented upgrade windows for kiota-java run from a few minutes to under an hour depending on cluster size. Test in a staging environment first and follow the vendor's documented HA upgrade order.

References

*This guide was assembled from the official vendor advisory, the NVD record, and the CISA KEV catalog entry on 2026-05-25. Always confirm against the vendor advisory before applying changes in production.*