{"id":"CVE-2026-48736","aliases":["GHSA-38cx-cq6f-5755"],"title":"Symfony: IpUtils::PRIVATE_SUBNETS Omits IPv6 Transition Forms (6to4, NAT64, Teredo, IPv4-compatible): SSRF Bypass in NoPrivateNetworkHttpClient","summary":"Symfony: IpUtils::PRIVATE_SUBNETS Omits IPv6 Transition Forms (6to4, NAT64, Teredo, IPv4-compatible): SSRF Bypass in NoPrivateNetworkHttpClient","severity":"medium","cwe":["CWE-184","CWE-918"],"vendor":"symfony","product":"symfony/http-client","ecosystem":"composer","affected":["symfony/http-client >= 5.4.0, < 5.4.53","symfony/http-foundation >= 6.4.0, < 6.4.41","symfony/http-foundation >= 7.0.0, < 7.4.13","symfony/http-foundation >= 8.0.0, < 8.0.13","symfony/symfony >= 5.4.0, < 5.4.53","symfony/symfony >= 6.4.0, < 6.4.41","symfony/symfony >= 7.0.0, < 7.4.13","symfony/symfony >= 8.0.0, < 8.0.13"],"patched":["symfony/http-client 5.4.53","symfony/http-foundation 6.4.41","symfony/http-foundation 7.4.13","symfony/http-foundation 8.0.13","symfony/symfony 5.4.53","symfony/symfony 6.4.41","symfony/symfony 7.4.13","symfony/symfony 8.0.13"],"published":"2026-06-15","updated":"2026-06-15","source":"GHSA","sourceUrl":"https://github.com/advisories/GHSA-38cx-cq6f-5755","references":[{"url":"https://github.com/symfony/symfony/security/advisories/GHSA-38cx-cq6f-5755"},{"url":"https://github.com/symfony/symfony/commit/82765368cf74177c36613575182f168a2eb765b2"},{"url":"https://github.com/symfony/symfony/commit/85b831555be8ea1f43bf01078afe87bc4c92f65e"},{"url":"https://github.com/FriendsOfPHP/security-advisories/blob/master/symfony/http-client/CVE-2026-48736.yaml"},{"url":"https://github.com/FriendsOfPHP/security-advisories/blob/master/symfony/http-foundation/CVE-2026-48736.yaml"},{"url":"https://github.com/FriendsOfPHP/security-advisories/blob/master/symfony/symfony/CVE-2026-48736.yaml"},{"url":"https://symfony.com/cve-2026-48736"},{"url":"https://github.com/advisories/GHSA-38cx-cq6f-5755"}],"tags":["ghsa","composer"],"ingestedAt":"2026-07-07T15:41:58.734Z","epss":0.0057,"epssPercentile":0.4598,"slug":"CVE-2026-48736","body":"## Overview\n\n### Description\n\n`Symfony\\Component\\HttpClient\\NoPrivateNetworkHttpClient` is documented as a decorator that blocks requests to private networks by default. The list of blocked subnets (`Symfony\\Component\\HttpFoundation\\IpUtils::PRIVATE_SUBNETS` on 6.4+, a private constant in `NoPrivateNetworkHttpClient` on 5.4) enumerates RFC1918, loopback, link-local and IPv4-mapped IPv6 (`::ffff:0:0/96`) prefixes, but omits the remaining IPv6 transition forms that can embed a private IPv4 destination: 6to4 (`2002::/16`, RFC 3056), Teredo (`2001::/32`, RFC 4380), NAT64 (`64:ff9b::/96`, RFC 6052 and `64:ff9b:1::/48`, RFC 8215) and IPv4-compatible IPv6 (`::/96`, RFC 4291 §2.5.5.1).\n\n`IpUtils::checkIp6()` is a pure bitwise CIDR comparison against the constants list and never extracts the embedded IPv4, so an attacker who can supply a URL writes the loopback / RFC1918 IPv4 target as e.g. `http://[2002:7f00:1::]/` (6to4 → 127.0.0.1), `http://[64:ff9b::7f00:1]/` (NAT64 → 127.0.0.1), `http://[::7f00:1]/` (IPv4-compatible → 127.0.0.1) or `http://[2001::1]/` (Teredo). `IpUtils::isPrivateIp()` returns `false` and `NoPrivateNetworkHttpClient` dispatches the request.\n\nReal-world reachability of the embedded IPv4 depends on the deploy's IPv6 routing (6to4 tunnel interface, upstream NAT64 gateway, kernel handling of IPv4-compatible addresses), but the security boundary the decorator promises — the dispatch decision — is crossed regardless of whether the packet ultimately lands on the embedded IPv4.\n\n### Resolution\n\nThe private-subnet list now includes `::/96`, `2002::/16`, `2001::/32`, `64:ff9b::/96` and `64:ff9b:1::/48`. Blanket blocking of these prefixes matches the policy applied by Chromium and Mozilla's Private Network Access; server-side HTTPS APIs are not legitimately published on these prefixes.\n\nThe patches for this issue are available [here](https://github.com/symfony/symfony/commit/82765368cf74177c36613575182f168a2eb765b2) for branch 5.4 and [here](https://github.com/symfony/symfony/commit/85b831555be8ea1f43bf01078afe87bc4c92f65e) for branch 6.4 (and forward-ported to 7.4, 8.0 and 8.1).\n\n### Credits\n\nSymfony would like to thank tonghuaroot for reporting the issue and Nicolas Grekas for providing the fix.\n\n## Affected packages\n\n- `symfony/http-client >= 5.4.0, < 5.4.53`\n- `symfony/http-foundation >= 6.4.0, < 6.4.41`\n- `symfony/http-foundation >= 7.0.0, < 7.4.13`\n- `symfony/http-foundation >= 8.0.0, < 8.0.13`\n- `symfony/symfony >= 5.4.0, < 5.4.53`\n- `symfony/symfony >= 6.4.0, < 6.4.41`\n- `symfony/symfony >= 7.0.0, < 7.4.13`\n- `symfony/symfony >= 8.0.0, < 8.0.13`\n\n## Remediation\n\nUpgrade to a patched release:\n\n- `symfony/http-client 5.4.53`\n- `symfony/http-foundation 6.4.41`\n- `symfony/http-foundation 7.4.13`\n- `symfony/http-foundation 8.0.13`\n- `symfony/symfony 5.4.53`\n- `symfony/symfony 6.4.41`\n- `symfony/symfony 7.4.13`\n- `symfony/symfony 8.0.13`","depth":"sunlit","depthScore":28,"depthScoreParts":{"impact":27.5,"likelihood":0.1,"exploitation":0,"ransomware":0},"changes":[]}