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VULNERABILITIES

CVE-2026-77866 Details

Description

Server-Side Request Forgery (SSRF) vulnerability in Slab safeurl allows an attacker who controls a validated URL to reach internal network destinations the library is configured to block. Only IPv4 addresses are matched against the reserved ranges and the blocklist. Every other address is treated as matching nothing, so a destination that is rejected in its IPv4 form is accepted when written as an IPv6 address, IPv6 entries in the blocklist never match, and a host that resolves to no IPv4 address is accepted regardless of where it points. Deployments that rely on the allowlist instead are unaffected, because there an unmatched address is rejected. This issue affects safeurl: from 0.1.0 onward.

Metrics

CVSS 3.x Severity and Vector Strings:

No CVSS 3.x data is available for this CVE.

References to Advisories, Solutions, and Tools

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URLSource(s)Tag(s)
https://cna.erlef.org/cves/CVE-2026-77866.html EEF
https://github.com/slab/safeurl-elixir/commit/feabbd0a13f83028ab24b71710526e9da9841f70 EEF
https://osv.dev/vulnerability/EEF-CVE-2026-77866 EEF

Weakness Enumeration

CWE-IDCWE NameSource
CWE-636Not Failing Securely ('Failing Open')EEF
CWE-918Server-Side Request Forgery (SSRF)EEF

Affected Products

No affected product data is available for this CVE.

Change History

2 change records found show changes

QUICK INFO

CVE Dictionary Entry:
CVE-2026-77866
NVD Published Date:
Sep 15, 2026
NVD Last Modified:
Sep 21, 2026
Source:
EEF
CVE-2026-77866 Details - Not Deferred