Vulnerability · Published Nov 5, 2026 · Assigned by Checkmarx
CVE-2026-123125Symfony: Ip Constraint public/private Modes Accept IPv4-Mapped and IPv4-Compatible IPv6 Addresses allowing SSRF Filter Bypass
Medium 6.5
In plain English
A medium-severity server-side request forgery in symfony from sensiolabs. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.2% (higher than 11% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official description
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.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian:12 | symfony | no fix listed | DEBIAN-CVE-2026-123125 |
| Debian:13 | symfony | no fix listed | DEBIAN-CVE-2026-123125 |
| Debian:14 | symfony | 7.4.23+dfsg-1 | DEBIAN-CVE-2026-123125 |
| Ubuntu:26.04:LTS | symfony | no fix listed | UBUNTU-CVE-2026-123125 |
| Ubuntu:26.10 | symfony | no fix listed | UBUNTU-CVE-2026-123125 |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| sensiolabs | symfony | 0 – before 5.4.566.0.0 – before 6.4.507.0.0 – before 7.4.238.0.0 – before 8.1.11 |
Weakness: CWE-184, CWE-918 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N