CVE-2026-77866

SSRF protection bypass in safeurl via IPv6 addresses and unresolvable hosts

CVSS 4.0 9.0 CRITICALCheck source for fixed versionsKEV status unknown

Original advisory

cve-program · CVE-2026-77866

Published

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.

Read the publisher's advisory

Affected versions, risk and source history

cve-program · CVE-2026-77866

Published

safeurl

https://repo.hex.pm

Publisher's version information

Shown as published. These rules are not interpreted as NuGet package version ranges.

{
                    "collectionURL": "https://repo.hex.pm",
                    "cpes": [
                        "cpe:2.3:a:slab:safeurl:*:*:*:*:*:*:*:*"
                    ],
                    "defaultStatus": "unaffected",
                    "modules": [
                        "'Elixir.SafeURL'"
                    ],
                    "packageName": "safeurl",
                    "packageURL": "pkg:hex/safeurl",
                    "product": "safeurl",
                    "programFiles": [
                        "lib/safeurl/safeurl.ex"
                    ],
                    "programRoutines": [
                        {
                            "name": "'Elixir.SafeURL':validate/2"
                        },
                        {
                            "name": "'Elixir.SafeURL':allowed?/2"
                        }
                    ],
                    "repo": "https://github.com/slab/safeurl-elixir",
                    "vendor": "Slab",
                    "versions": [
                        {
                            "lessThan": "*",
                            "status": "affected",
                            "version": "0.1.0",
                            "versionType": "semver"
                        }
                    ]
                }

slab/safeurl-elixir

https://github.com

Publisher's version information

Shown as published. These rules are not interpreted as NuGet package version ranges.

{
                    "collectionURL": "https://github.com",
                    "cpes": [
                        "cpe:2.3:a:slab:safeurl:*:*:*:*:*:*:*:*"
                    ],
                    "defaultStatus": "unaffected",
                    "modules": [
                        "'Elixir.SafeURL'"
                    ],
                    "packageName": "slab/safeurl-elixir",
                    "packageURL": "pkg:github/slab/safeurl-elixir",
                    "product": "safeurl",
                    "programFiles": [
                        "lib/safeurl/safeurl.ex"
                    ],
                    "programRoutines": [
                        {
                            "name": "'Elixir.SafeURL':validate/2"
                        },
                        {
                            "name": "'Elixir.SafeURL':allowed?/2"
                        }
                    ],
                    "repo": "https://github.com/slab/safeurl-elixir",
                    "vendor": "Slab",
                    "versions": [
                        {
                            "lessThan": "*",
                            "status": "affected",
                            "version": "feabbd0a13f83028ab24b71710526e9da9841f70",
                            "versionType": "git"
                        }
                    ]
                }

Original source record · Cite this exact observation · Complete original publisher JSON