ChangeIntel IT change radar
Public mode

No access to your tenant or devices. Every item links to its source. What this means

Sources need attention Customize Public modeDiscuss ChangeIntel on Discord
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

Exploitation and risk

Source status

CISA KEV lists vulnerabilities known to be exploited. FIRST EPSS estimates the likelihood of exploitation in the next 30 days. An unavailable score does not mean zero risk.

Which CVEs have scores here?

This view includes predictions for CVE identifiers explicitly listed in public NuGet advisories. Microsoft release pages have their own prediction coverage. Check source status for the scope and latest checks.

No exploitation or prediction data is available here for these CVEs. This does not mean they are safe or unlikely to be exploited.

cve-program · CVE-2026-77866

Published

SSRF protection bypass in safeurl via IPv6 addresses and unresolvable hosts

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.

Source published
15 Sep 2026 15:38:15 UTC
Source modified
21 Sep 2026 18:44:55 UTC
Saved here
23 Oct 2026 15:48:27 UTC
Source terms
CVE Program Terms of Use

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

Source: cve-program · CVE Program Terms of Use. The publisher's wording is preserved. ChangeIntel groups the information and labels changes. The JSON record includes additional source fields.

CVSS 4.0 · 9.0 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

ChangeIntel

An IT change radar: releases, security, known issues, retirements, documentation changes, and service status from public sources. Every item links to supporting evidence; dates and statuses can change after they are read.

Sources read 12 Nov 23:52 UTC · 273 of 275 readable · 271 fully read · documentation 469/469 current

No accounts or analytics; your preferences stay in your browser. Information, not advice. ChangeIntel is an independent tool and is not affiliated with or endorsed by Microsoft, Apple, Google, Broadcom (VMware), Jamf, Oracle, Mozilla, or any other vendor it covers. Product names are trademarks of their owners. Built by Evotec.