CVE-2026-49859: CWE-693: Protection Mechanism Failure in denoland deno
Deno versions prior to 2.8.1 contain a vulnerability where the fetch() function enforces network restrictions based on hostname checks but fails to verify the resolved IP addresses against deny-net rules. This allows an attacker to bypass network restrictions by using a domain name that passes hostname validation but resolves to a denied IP address. The issue is fixed in version 2.8.1.
AI Analysis
Technical Summary
CVE-2026-49859 describes a protection mechanism failure in the Deno runtime before version 2.8.1. When the fetch() API was called, Deno checked the destination hostname against configured --deny-net rules but did not re-validate the IP addresses that the hostname resolved to. An attacker-controlled script could exploit this by using a crafted domain name that passes the hostname check but resolves to an IP address that should be denied, effectively bypassing network restrictions. This vulnerability is addressed in Deno 2.8.1.
Potential Impact
The vulnerability allows bypassing of network access restrictions configured via --deny-net rules, potentially enabling unauthorized network communication to IP addresses that should be blocked. This can lead to information disclosure or unauthorized interactions with restricted network resources. The CVSS score of 5.2 (medium severity) reflects limited impact with requirements for local privileges and low attack complexity.
Mitigation Recommendations
Upgrade Deno to version 2.8.1 or later, where this vulnerability is fixed. No other mitigations are specified. Patch status is confirmed by the vendor advisory stating the issue is fixed in 2.8.1.
CVE-2026-49859: CWE-693: Protection Mechanism Failure in denoland deno
Description
Deno versions prior to 2.8.1 contain a vulnerability where the fetch() function enforces network restrictions based on hostname checks but fails to verify the resolved IP addresses against deny-net rules. This allows an attacker to bypass network restrictions by using a domain name that passes hostname validation but resolves to a denied IP address. The issue is fixed in version 2.8.1.
CVSS v3.1
Score 5.2medium
Affected software
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AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
CVE-2026-49859 describes a protection mechanism failure in the Deno runtime before version 2.8.1. When the fetch() API was called, Deno checked the destination hostname against configured --deny-net rules but did not re-validate the IP addresses that the hostname resolved to. An attacker-controlled script could exploit this by using a crafted domain name that passes the hostname check but resolves to an IP address that should be denied, effectively bypassing network restrictions. This vulnerability is addressed in Deno 2.8.1.
Potential Impact
The vulnerability allows bypassing of network access restrictions configured via --deny-net rules, potentially enabling unauthorized network communication to IP addresses that should be blocked. This can lead to information disclosure or unauthorized interactions with restricted network resources. The CVSS score of 5.2 (medium severity) reflects limited impact with requirements for local privileges and low attack complexity.
Mitigation Recommendations
Upgrade Deno to version 2.8.1 or later, where this vulnerability is fixed. No other mitigations are specified. Patch status is confirmed by the vendor advisory stating the issue is fixed in 2.8.1.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- GitHub_M
- Date Reserved
- 2026-06-01T22:03:19.640Z
- Cvss Version
- 3.1
- State
- PUBLISHED
- Remediation Level
- null
Threat ID: 6a3ac4efeed863c81e61823e
Added to database: 06/23/2026, 17:39:59 UTC
Last enriched: 06/23/2026, 17:55:13 UTC
Last updated: 06/23/2026, 17:55:13 UTC
Views: 2
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