CVE-2026-82533: DeepSeek Harness < 0.1.2-alpha.1 Authentication Bypass via Host Header Spoofing
DeepSeek Harness before 0.1.2-alpha.1 contains an authentication bypass vulnerability that grants unauthenticated access to its local HTTP agent-control API by accepting a client-supplied loopback Host header in place of validating the actual TCP connection origin. On the default configuration, a confined tool-executed process can reach the loopback API without any port exposure and use it to escape its own OS sandbox, escalate to unconfined execution, and disable the approval prompt. When the port is externally reachable via tunnel, SSH forward, or reverse proxy, a remote attacker can exploit the same flaw to create sessions, execute arbitrary commands, and exfiltrate stored conversation transcripts without credentials.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade
DeepSeek Harnessto a version that resolves this vulnerability.Fixed in 0.1.2-alpha.1
Event History
Frequently Asked Questions
Which deployments are exposed?
Deployments running DeepSeek Harness before 0.1.2-alpha.1 are affected if an attacker can send requests to the local HTTP control-plane API. The issue is in validation of the client-supplied Host header rather than the actual TCP connection origin.
Does exploitation require credentials or an API key?
No. An attacker can bypass authentication by supplying a spoofed Host header, without any credential or API key. User interaction is required according to the supplied severity vector.
What access can an attacker obtain after bypassing authentication?
An attacker can gain full agent control, including invoking privileged commands such as commands/execute with danger-full-access permissions. They can also escalate session approval policies to unconfined execution and retrieve all stored conversations.
How can I determine whether my installation is affected?
Check the installed DeepSeek Harness version. Versions before 0.1.2-alpha.1 are affected; 0.1.2-alpha.1 is the referenced release containing the fix.