CVE-2025-26210: DeepSeek R1 · Cross-site Scripting
Source CVE Database V5
Not known to be exploited · CVSS 8.8 High.
Data as of 26 Oct 2026, 17:16 UTC
- EPSS
- 0.5% chance of exploitation in 30 days – higher than 47% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:HExploitation evidence
Disclosed: evidence found.
CVE published 3 Sep 2025
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.
What to do
AI-suggested
- Implement strict Content Security Policy (CSP) headers to restrict the execution of unauthorized scripts within the run-html-chat.deepseeksvc.com domain.
- Employ input validation and output encoding on all user-supplied data that is rendered in chat interfaces to prevent injection of malicious scripts.
- Use web application firewalls (WAFs) with rules tailored to detect and block XSS payloads targeting DeepSeek services.
- Educate users on the risks of interacting with unsolicited or suspicious chat messages and links, emphasizing cautious behavior to reduce successful social engineering.
- Monitor network traffic and logs for unusual activities indicative of exploitation attempts, such as anomalous script execution or unexpected requests to the chat domain.
- Isolate the DeepSeek chat service in a segmented network environment to limit lateral movement if exploitation occurs.
- Engage with DeepSeek vendors or service providers to obtain patches or updates as soon as they become available and plan for timely deployment.
- Consider temporary disabling or restricting access to the affected chat services if feasible until a fix is applied.
Description
DeepSeek R1 through V3.1 allows XSS, as demonstrated by JavaScript execution in the context of the run-html-chat.deepseeksvc.com domain. NOTE: some third parties have indicated that this is intended behavior.