CVE-2026-48736

MEDIUMPre-NVD 0.0
0.0
EchelonGraph verdictMonitorLow exploitation likelihood right now — keep watching.
  • No confirmed exploitation signals yet
CISA-KEV: Not listedEPSS: —CVSS: —Exploit: NoneExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

Symfony: IpUtils::PRIVATE_SUBNETS Omits IPv6 Transition Forms (6to4, NAT64, Teredo, IPv4-compatible): SSRF Bypass in NoPrivateNetworkHttpClient

Description

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).

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.

Real-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.

Resolution

The 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.

The patches for this issue are available here for branch 5.4 and here for branch 6.4 (and forward-ported to 7.4, 8.0 and 8.1).

Credits

Symfony would like to thank tonghuaroot for reporting the issue and Nicolas Grekas for providing the fix.

CVSS v3
—
EG Score
0.0(none)
EPSS
—
KEV
Not listed

Published

June 15, 2026

Last Modified

June 15, 2026

Vendor Advisories for CVE-2026-48736(1)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Affected Packages

(3 across 1 ecosystem)
Packagist(3)
PackageVulnerable rangeFixed inDependents
symfony/http-clientv5.4.0 ... v5.4.9 (41 versions)5.4.53—
symfony/http-foundationv8.0.0 ... v8.0.8 (8 versions)8.0.13—
symfony/symfonyv8.0.0 ... v8.0.9 (13 versions)8.0.13—

Data Freshness Timeline

(refreshed 0× in last 7d / 1× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

  1. 2026-06-15 17:45 UTCEG score recompute

Frequently asked(3)

What is CVE-2026-48736?
CVE-2026-48736 is a medium vulnerability published on June 15, 2026. Symfony: IpUtils::PRIVATE_SUBNETS Omits IPv6 Transition Forms (6to4, NAT64, Teredo, IPv4-compatible): SSRF Bypass in NoPrivateNetworkHttpClient Description Symfony\Component\HttpClient\NoPrivateNetworkHttpClient is documented as a decorator that blocks requests to private networks by default. The…
When was CVE-2026-48736 disclosed?
CVE-2026-48736 was first published in the National Vulnerability Database on June 15, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
How do I remediate CVE-2026-48736?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2026-48736, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

Dependency Blast Radius

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