A data exfiltration vulnerability exists in Anthropic’s deprecated Slack Model Context Protocol (MCP) Server via automatic link unfurling. When an AI agent using the Slack MCP Server processes untrusted data, it can be manipulated to generate messages containing attacker-crafted hyperlinks embedding sensitive data. Slack’s link preview bots (e.g., Slack-LinkExpanding, Slackbot, Slack-ImgProxy) will then issue outbound requests to the attacker-controlled URL, resulting in zero-click exfiltration of private data.
CVE-2025-34072
This critical-severity CVE scores 9.3 under NVD CVSS v3. EPSS exploit probability: 0.4%, top 70% of all CVEs by exploit prediction. GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).
- High severity, but no confirmed exploitation yet
No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.
- CVSS v3
- 9.3
- EG Score
- 9.3(medium)
- EG Risk
- 58(Track)EG Risk 58/100SSVC: Track
EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).
How it’s computedSeverity93% × 45%Exploitation40% × 40%Automatability0% × 15%Action: Routine — remediate on your standard cadence. - EPSS PROB
- 0%
- EPSS %ILE
- 30%
- KEV
- Not listed
Published
July 2, 2025
Last Modified
April 15, 2026
Advisory Details (2)
Auto-updated Aug 1, 2026Anthropic Slack MCP Server Data Exfiltration via Link Unfurling | Advisories | VulnCheck
https://vulncheck.com/advisories/anthropic-slack-mcp-server-data-exfiltrationSecurity Advisory: Anthropic's Slack MCP Server Vulnerable to Data Exfiltration · Embrace The Red
https://embracethered.com/blog/posts/2025/security-advisory-anthropic-slack-mcp-server-data-leakage/Weakness Classification(2)
MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.
Data Freshness Timeline
(refreshed 6× in last 7d / 38× in last 30d)
Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.
Showing the most recent 100 of 139 total refreshes for this CVE.
- 2026-08-07 16:26 UTCEPSS rescore
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- 2026-06-08 16:02 UTCEG score recompute▲ 9.30
- 2026-06-08 16:02 UTCGHSA enrichment
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Related CVEs(same CWE)
Same CWE
10 shownCWE-20 · CWE-200
Frequently asked(5)
What is CVE-2025-34072?
When was CVE-2025-34072 disclosed?
Is CVE-2025-34072 actively exploited?
What is the CVSS score of CVE-2025-34072?
How do I remediate CVE-2025-34072?
Dependency Blast Radius
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