DeepSeek Harness (dsh): Prompt injection via context compaction
Summary
DeepSeek Harness (dsh), an AI coding-agent runtime, replaces conversation history during context compaction with a model-generated summary that becomes the entire context of the resumed session. Instructions injected into external content such as web pages, emails or repository files can be reproduced verbatim in this summary and carried into the resumed session as established tasks. Under the conditions described, an attacker could use this for silent network exfiltration of workspace data, since network egress of the resumed session is unrestricted.
Affected
- DeepSeek Harness (dsh), developer preview, commit c291e796 (2026-09)
- Package: @deepseek-ai/dsh-compaction-basic
- No release version range known.
Fixed in
Unknown.
Workaround
- No vendor-documented mitigation found.
- Limit which external content agents can ingest (web pages, repositories, documents, tool output).
- Keep human approval prompts enabled.
- Do not treat the sandbox as a security boundary; it does not prevent network egress.
Exploitation
- No exploitation reported in the wild.
- No public proof of concept confirmed; a PoC repository is referenced in the CVE record.
- CISA SSVC: Exploitation none, Automatable no, Technical Impact total.
Our recommendation
- Inventory whether dsh is installed on workstations or CI runners.
- Pause or restrict use of dsh with untrusted repositories, web content or emails until a vendor fix is confirmed.
- Remove credentials and restrict shell and network access for agents that process untrusted content.
- Monitor outbound network traffic from agent hosts.
- Verify the NVD status and the vendor advisory for a fixed version.
Public exploits
PoC-in-GitHub, Metasploit and Exploit-DB list nothing for this CVE.
Research sources
- NVD / CVE record source: OpenCVE app.opencve.io
- VulDB 421297 vuldb.com
- Strix CVE-2026-95183 www.strix.ai
- Vendor compaction README github.com
- Referenced gist gist.github.com
- CNNVD CNNVD-2026-93031746 vulners.com
Researched and written up in English and German by an AI (Claude by Anthropic) based on NVD, CISA, EPSS and the sources listed. The vendor information is authoritative. Researched on 31 Oct 2026, 16:02.
Original description (NVD)
An issue in the context-compaction feature of DeepSeek Harness (dsh) commit c291e796 allows attackers to execute a prompt injection attack via crafted external content.
Sources
The tracker combines official, freely usable data sources – updated continuously:
- NVD (NIST) – CVEs, rating (CVSS), affected products
- CISA KEV – vulnerabilities confirmed by CISA as actively exploited
- CISA Vulnrichment – CISA assessment (SSVC) in the official CVE record
- FIRST EPSS – probability of exploitation
- Microsoft MSRC – Patch Tuesday: vulnerabilities, severity, updates
- PoC-in-GitHub – public proof-of-concept repositories
- Metasploit (Rapid7) – modules of the Metasploit Framework
- Exploit-DB (OffSec) – archive of public exploits (links only)
- Patch days: official vendor pages (linked per vendor) (Vendor patch days)
This product uses data from the NVD API but is not endorsed or certified by the NVD. EPSS data © FIRST.org.
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