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.
Attack Parameters
Attack Vector
Network
Can be exploited remotely
Attack Complexity
Low
Easy to exploit
Attack Requirements
None
No additional conditions
Privileges Required
None
No privileges needed
User Interaction
Passive
Minimal interaction
Impact Assessment
Confidentiality
High
Complete data leak
Integrity
High
Complete data modification
Availability
High
Complete denial of service
CVSS Vector v4.0
Weakness Type (CWE)
References 4
https://github.com/deepseek-ai/deepseek-harness/commit/3e24087bfaeabe40b58ba2f7…
disclosure@vulncheck.com
https://github.com/deepseek-ai/deepseek-harness/releases/tag/dsh-v0.1.2-alpha.1
disclosure@vulncheck.com
https://www.vulncheck.com/advisories/deepseek-harness-alpha-1-authentication-by…
disclosure@vulncheck.com
https://www.ox.security/blog/cve-2026-82533-deepseek-harness-ai-agent-sandbox-e…
disclosure@vulncheck.com