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symfony/http-client: NoPrivateNetworkHttpClient now blocks IPv6 transition prefixes

The private-subnet list in NoPrivateNetworkHttpClient now includes IPv6 transition prefixes (::/96, 2002::/16, 2001::/32, 64:ff9b::/96, 64:ff9b:1::/48) to block

16 Jun 2026Read 1 minSeverity: schedule it

What changed

The private-subnet list in NoPrivateNetworkHttpClient now includes IPv6 transition prefixes (::/96, 2002::/16, 2001::/32, 64:ff9b::/96, 64:ff9b:1::/48) to block requests to private IPv4 addresses embedded in IPv6 addresses.

Who it affects

Users of Symfony HttpClient who rely on NoPrivateNetworkHttpClient to block requests to private networks.

What to do today

Update symfony/http-client to the latest patched version (5.4.x, 6.4.x, 7.4.x, 8.0.x, or 8.1.x) to ensure private network protection covers IPv6 transition mechanisms.

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