# CVE-2026-123125: Symfony: Ip Constraint public/private Modes Accept IPv4-Mapped and IPv4-Compatible IPv6 Addresses allowing SSRF Filter Bypass

Status: published. Published: 2026-11-05. Updated: 2026-11-05.

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.

## Remediation

- fix: The reporting source identifies this reference as a patch. Check the advisory for affected versions and supported release branches. (source: CNA: Checkmarx) — https://github.com/symfony/symfony/commit/3bf8ea37fcb402c5ecc502a3f63012df85a7572e

## Affected products and versions

- sensiolabs / symfony (symfony/validator): ≥ 0; < 5.4.56 (affected, git); ≥ 6.0.0; < 6.4.50 (affected, git); ≥ 7.0.0; < 7.4.23 (affected, git); ≥ 8.0.0; < 8.1.11 (affected, git). Source: CNA: Checkmarx

## Severity and prioritization

- CVSS 4.0: 6.3 (medium); CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N; source: CNA: Checkmarx

- CVSS 3.1: 6.5 (medium); CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N; source: ADP: CISA-ADP

- CISA KEV: No listing in collected sources

- EPSS: Not available

- SSVC: exploitation none; automatable yes; technical impact partial; source ADP: CISA-ADP

- Weaknesses: CWE-184, CWE-918

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://github.com/symfony/symfony/security/advisories/GHSA-4qpf-57w4-m3wc (CNA: Checkmarx; third-party-advisory)

- https://github.com/symfony/symfony/commit/3bf8ea37fcb402c5ecc502a3f63012df85a7572e (CNA: Checkmarx; patch)

## Provenance

- CNA: Checkmarx: https://www.cve.org/CVERecord?id=CVE-2026-123125; retrieved 2026-11-05; source updated 2026-11-05

Revision: 5d4152450186368659f158a71c1795782d8d6af64c8dcd6bac59441713765536

Canonical: https://y2.dev/cve/CVE-2026-123125

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