Bug 2567709 (CVE-2026-123125)

Summary: CVE-2026-123125 symfony/validator: Symfony Validator: Server-Side Request Forgery via incomplete IP address validation
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
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Priority: medium    
Version: unspecifiedKeywords: Security
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Hardware: All   
OS: Linux   
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A flaw was found in the Symfony Validator component. The IP address validator improperly classifies certain internal and reserved network addresses as public, such as shared address spaces and IPv6 addresses embedding internal IPv4 addresses. A remote attacker can exploit this flaw by submitting specially crafted IP addresses to bypass validation, potentially leading to Server-Side Request Forgery (SSRF) and unauthorized access to internal network resources.
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Description OSIDB Bzimport 2026-11-05 22:19:47 UTC 
The Symfony Validator component IpValidator incompletely classifies internal addresses in the filtered modes of the Ip constraint, so some internal addresses are accepted as public, which can lead to Server-Side Request Forgery (SSRF) in Symfony versions prior to 5.4.56, 6.x prior to 6.4.50, 7.x prior to 7.4.23, and 8.x prior to 8.1.11.

In these modes, IpValidator relies on the PHP flags FILTER_FLAG_NO_PRIV_RANGE and FILTER_FLAG_NO_RES_RANGE to classify addresses as public, private, or reserved. These flags do not cover shared address space (100.64.0.0/10) or IPv4-mapped, IPv4-compatible, and 6to4 IPv6 addresses, which can embed internal IPv4 addresses. A value such as ::ffff:127.0.0.1 can therefore pass validation even though it points to an internal host.
Applications that rely on the Ip constraint to reject internal addresses, for example before making a server-side request to a user-supplied address, can be exposed to SSRF.