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CVE

EEF-CVE-2026-77866

SSRF protection bypass in safeurl via IPv6 addresses and unresolvable hosts
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CVE

EEF-CVE-2026-77866

SSRF protection bypass in safeurl via IPv6 addresses and unresolvable hosts

Summary

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.

Package Versions Affected

Package Version
patch Availability
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CVSS Version

Severity
Base Score
CVSS Version
Score Vector
C
H
U
9
-
4.0
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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
C
H
U
0
-
C
H
U
-

Related Resources

No items found.

References

https://cna.erlef.org/cves/CVE-2026-77866.html, https://github.com/slab/safeurl-elixir/commit/feabbd0a13f83028ab24b71710526e9da9841f70, https://hex.pm/packages/safeurl

Severity

0

CVSS Score
0
10

Basic Information

Base CVSS
0
EPSS Probability
0.0048%
EPSS Percentile
0.39449%
Introduced Version
0.1.0,feabbd0a13f83028ab24b71710526e9da9841f70
Fix Available

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