CVE-2026-59563 HMAC Confirmation Token Unbinding in zscaler-mcp-server
Attackers can replay HMAC tokens across resources, allowing unauthorized modification of data in Zscaler MCP Server.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- None listed
What is CVE-2026-59563?
CVE-2026-59563 is a medium-severity vulnerability in zscaler-mcp-server, published on 28 Sep 2026. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link.
Official description
Zscaler MCP Server versions 0.7.0 and 0.7.1 has an issue where HMAC confirmation tokens were not bound to the target resource identifier, allowing an MCP client or agent to replay a token generated for one resource to affect another resource of the same type. This issue is fixed in version 0.7.2.
Weakness: CWE-305
Which versions are affected by CVE-2026-59563?
How do I fix CVE-2026-59563?
No fix has been published for CVE-2026-59563 yet. Limit exposure of the affected software until one is available.
Is CVE-2026-59563 being exploited?
There is no known exploitation of CVE-2026-59563 in the wild and no public exploit code.
Sources
Also known as GHSA-6wjq-5f4c-p8f7.