MediumCVE-2026-121619

SensioLabs Symfony: Authentication Bypass by Spoofing (CVE-2026-121619)

Published 12.11.2026Last modified 12.11.2026Sources: EUVD, CVE.org

What is affected, what to do

The available sources name no fixed version. Check the vendor guidance in the references below.

Not sure whether and how you are affected? Ask a question about this vulnerability

Metrics

6.3

XIEM Effective CVSS

Highest available CVSS rating from NVD and vendor data.

Source: Vendor (CNA), CVSS v4

6.3

CVSS v4

Severity Medium on the scale from 0 to 10.

Source: EUVD, CVE.org

—

EPSS score

No value is available for this vulnerability.

Show all metrics

Severity: Medium
Priority (0–325) The priority score is a consolidated metric that condenses several individual signals into a single, action-guiding ranking: technical severity (CVSS), exploitation likelihood (EPSS), known-exploited status (KEV) and the context of the affected asset. The aim is to answer the only truly important question in vulnerability management: what first? Read in glossary: 61.50 Methodology
Exploit maturity An exploit is code or a technique that specifically uses a concrete vulnerability to force unintended behaviour — such as executing code or escalating privileges. It is the tool that turns a theoretical flaw into a practical attack. Read in glossary: no public PoC known
XIEM Effective CVSS XIEM® is the tiered managed-security operating model from NEOSEC and a registered trademark of NEOSEC GmbH. It extends classic SIEM — the central collection, normalisation and correlation of security-relevant events — with endpoint forensics, network visibility and deception technology, and consolidates them into three building tiers: Sentry, Orchestrate and Command. Read in glossary: 6.3 Methodology
CVSS v4 CVSS is the globally established, open standard for assessing the technical severity of a vulnerability on a scale from 0 to 10. It describes how easily a flaw can be exploited and what damage it can cause — but not how likely its actual exploitation is. CVSS and the complementary EPSS deliberately answer different questions. Read in glossary: 6.3
KEV status The KEV catalogue is a list maintained by the US authority CISA of vulnerabilities for which active exploitation in the wild has been confirmed. It answers not the question „how severe?“ but „is it already being attacked?“ — thereby sharply prioritising patching. Read in glossary: —
Published: 12.11.2026
CWE CWE is a catalogue of typical weakness types in software and hardware — such as flawed input validation, unsafe memory handling or poor authentication. Where a CVE names a concrete vulnerability in a concrete product, a CWE describes the underlying class of defect. Read in glossary: CWE-290, CWE-348

Detection rules

No NEOSEC detection rule is available for this vulnerability yet.

Classification under NIS2 and CRA

Rule-based classification from exploitation status and severity. It does not replace a case-by-case assessment.

NIS2 NIS2 is EU Directive (EU) 2022/2555 to raise the level of cybersecurity across the Union. It substantially broadens obligations compared with the first NIS directive: more sectors, mandatory risk management, staged reporting duties and personal accountability of senior management. Read in glossary: Handle the vulnerability in regular vulnerability handling under Art. 21(2)(e) NIS2.
CRA The CRA is EU Regulation (EU) 2024/2847 setting horizontal cybersecurity requirements for „products with digital elements“ — from industrial controllers and software to connected consumer devices. For the first time manufacturers must ensure security across the entire product lifecycle, handle vulnerabilities and provide security updates. Read in glossary: From 11.12.2027, Annex I Part II CRA requires manufacturers of affected products with digital elements to handle vulnerabilities without delay and provide security updates.
ISO/IEC 27001 ISO/IEC 27001 is the internationally leading standard for an information security management system (ISMS). It describes a risk-based, process-oriented framework to systematically plan, implement, review and improve information security. Read in glossary: Control A.8.8, management of technical vulnerabilities: assess relevance to your systems, plan remediation and keep evidence.

Description

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.

Source: ENISA EUVD, cvelistv5, NVD (NIST), CVE.org (MITRE)

Affected products

The following versions are affected. Older releases of the same product line are also vulnerable unless stated otherwise.

Affected products
		Affected versions	Fixed in
sensiolabs	symfony	`—`	—

Vendors and products

Sensiolabs SensioLabs Symfony

Weakness classes (CWE)

CWE-290Authentication Bypass by Spoofing
Base
This attack-focused weakness is caused by incorrectly implemented authentication schemes that are subject to spoofing attacks.
Entry at MITRE CWE-290
CWE-348Use of Less Trusted Source
Base
The product has two different sources of the same data or information, but it uses the source that has less support for verification, is less trusted, or is less resistant to attack.
Entry at MITRE CWE-348

References & sources

github.comsymfony/symfony/security/advisories/GHSA-xg2q-4rrq-657qeuvd, Third-party advisory
github.comsymfony/symfony/commit/e109aa54d42678e2a72ec148092a8453a67de931euvd, Patch
NVD (NIST)vuln/detail/CVE-2026-121619euvd

Changes to this CVE

Who changed this CVE and when: NVD (analysis, affected products, CVSS), the CVE publisher (CNA) and additional providers such as CISA (ADP).

12.11.2026Received596c5446…

CVSS V4.0: AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N

Weakness type: CWE-290, CWE-348

Description added or changed

New references:

Show 7 original changes

Individual changes of this event as published by NVD
Type	Action	Before	After
Description	added	—	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.
CVSS	added	—	AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/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
Weakness type (CWE)	added	—	CWE-290
Weakness type (CWE)	added	—	CWE-348
Affected versions (publisher)	added	—	New affected value received. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/121xxx/CVE-2026-121619.json">CVE-2026-121619</a>
Reference	added	—	https://github.com/symfony/symfony/commit/e109aa54d42678e2a72ec148092a8453a67de931
Reference	added	—	https://github.com/symfony/symfony/security/advisories/GHSA-xg2q-4rrq-657q

Source identifier: 596c5446-0ce5-4ba2-aa66-48b3b757a647

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