CVE-2026-77866

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Source

https://cve.org/CVERecord?id=CVE-2026-77866

Import Source

https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-77866.json

JSON Data

https://api.osv.dev/v1/vulns/CVE-2026-77866

Aliases

EEF-CVE-2026-77866

Published

2026-09-15T15:38:15Z

Modified

2026-09-18T03:30:34Z

Severity

9.0 (Critical) CVSS_V4 - CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:L/VA:N/SC:H/SI:L/SA:N CVSS Calculator

Summary

SSRF protection bypass in safeurl via IPv6 addresses and unresolvable hosts

Details

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.

Database specific

{
    "cna_assigner": "EEF",
    "cwe_ids": [
        "CWE-636",
        "CWE-918"
    ],
    "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/77xxx/CVE-2026-77866.json",
    "unresolved_ranges": [
        {
            "extracted_events": [
                {
                    "introduced": "0.1.0"
                },
                {
                    "fixed": "*"
                },
                {
                    "introduced": "feabbd0a13f83028ab24b71710526e9da9841f70"
                },
                {
                    "fixed": "*"
                }
            ],
            "source": "AFFECTED_FIELD"
        }
    ]
}

References

Affected packages

Git / github.com/slab/safeurl-elixir

Affected ranges

Type

GIT

Repo

https://github.com/slab/safeurl-elixir

Events

Introduced

Fixed

feabbd0a13f83028ab24b71710526e9da9841f70

Database specific

Show details

{
    "source": "REFERENCES"
}

Database specific

source

"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-77866.json"