CVE-2026-121619

What it is

The Symfony FrameworkBundle framework.trusted_proxies option and the HttpFoundation Request::setTrustedProxies() method trust remote clients as reverse proxies when the private_ranges shortcut is used, allowing remote attackers to spoof the client IP address, host and scheme in Symfony FrameworkBundle versions 7.1 prior to 7.4.23 and 8.x prior to 8.1.11, and HttpFoundation versions 7.2 prior to 7.4.23 and 8.x prior to 8.1.11. The private_ranges and PRIVATE_SUBNETS keywords resolved to IpUtils::PRIVATE_SUBNETS, the deny list of NoPrivateNetworkHttpClient, which lists the private and special-purpose prefixes a server must not connect to. Since the fix for CVE-2026-48736 (7.4.13 and 8.0.13), this list also covers the IPv6 prefixes that embed an IPv4 address: IPv4-mapped (::ffff:0:0/96), IPv4-compatible (::/96), 6to4 (2002::/16), Teredo (2001::/32) and NAT64 (64:ff9b::/96). The IPv4-mapped entry has been in the list since the private_ranges shortcut was introduced, in 7.1 for framework.trusted_proxies and in 7.2 for Request::setTrustedProxies(). Over-blocking is safe for a deny list, but when the same entries are used as the allow list of trusted proxies, they trust remote clients. A client whose connection arrives with such a source address is treated as a reverse proxy, and the X-Forwarded-For, X-Forwarded-Host, X-Forwarded-Proto, X-Forwarded-Port and X-Forwarded-Prefix headers it sends are honoured. For example, with Request::setTrustedProxies(['private_ranges'], ...), a request with REMOTE_ADDR set to ::ffff:203.0.113.7 and the headers X-Forwarded-For: 10.0.0.9, X-Forwarded-Host: evil.example.com and X-Forwarded-Proto: https makes getClientIp() return 10.0.0.9, getHost() return evil.example.com and isSecure() return true. Two kinds of deployments are exposed: a server listening on the IPv6 wildcard address without IPV6_V6ONLY reports every IPv4 client in the IPv4-mapped form, so every client is trusted, and a server reachable over IPv6 trusts any client sourcing from 6to4 or Teredo space, which is globally routed, whatever its listener. A spoofed client address defeats IP allow lists, rate limiting and audit logs; a spoofed host poisons the URLs written into password reset and login link e-mails and into shared caches; a spoofed scheme satisfies requires_channel: https over plain HTTP. Symfony 6.4 does not point any trusted proxy setting at IpUtils::PRIVATE_SUBNETS and is not affected by default, but an application that passes that constant to Request::setTrustedProxies() itself could be exposed in the same way on any version. This issue is fixed in 7.4.23 and 8.1.11.

At a glance

Exploitability

Can be exploited over the network without logging in. Limited direct impact.

Exploit odds

0.2% chance of exploitation in the next 30 days (EPSS).

Fix

A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

1. 2026-11-03 16:42 UTC ReservedThe CVE id was reserved by its CNA
2. 2026-11-12 19:16 UTC PublishedDisclosed publicly on CVE.org and NVD
3. 2026-11-12 19:16 UTC Last updatedMost recent change to the record

Why it ranks here

• Exploited in the wild: no, CISA does not list it.
• Exploit odds: 0.2% in the next 30 days (EPSS).
• Severity: 6.3 MEDIUM (CVSS).
• Fix: a patch or advisory is linked.

Details

Published

2026-11-12 19:16 UTC

Last modified

2026-11-12 19:16 UTC

Exploit probability

0.2% · EPSS, next 30 days

Weakness

CWE-290

Record status

Awaiting Analysis

Attack profile CVSS 4.0 · 6.3

Attack vector

Network

Complexity

Low

Attack requirements

Present

Privileges needed

None

User interaction

None

Confidentiality

Low

Integrity

Low

Availability

None

Is it in your code?

Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.

Read https://cve-list.com/agent/cve/CVE-2026-121619.md and follow it. Check whether this project is affected by CVE-2026-121619. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.

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