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CVE-2026-45074 – Authentication Bypass – Symfony security-http 7.1.0–7.4.11 / 8.0.0–8.0.11

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Summary

CVE-2026-45074 is a high-severity authentication bypass vulnerability in the symfony/security-http component, affecting Symfony versions 7.1.0 through 7.4.11 and 8.0.0 through 8.0.11. The flaw allows an attacker who controls another application registered on the same Central Authentication Service (CAS) server to replay a victim’s authentication ticket and impersonate that user, achieving full account takeover without valid credentials. Patches are available in Symfony 7.4.12 and 8.0.12.

Technical details

  • Root cause: Cas2Handler constructs the CAS service parameter by calling Request::getSchemeAndHttpHost(), which reflects the value of the HTTP Host header from the incoming request. When framework.trusted_hosts is not configured — the default state in Symfony — this value is entirely attacker-controlled.
  • Trigger conditions: The vulnerability is present in any Symfony application that uses CAS authentication via Cas2Handler and has not explicitly configured framework.trusted_hosts (or called Request::setTrustedHosts()).
  • Attack vector: A network-accessible attacker who controls any other application registered with the same CAS server can craft a request with a spoofed Host header pointing to their controlled application, obtain or intercept a victim’s CAS service ticket, and replay it against the target Symfony application. Because the service URL is derived from the spoofed header, the CAS server validates the ticket as legitimate for the attacker’s registered service.
  • Impact: Successful exploitation results in complete authentication bypass — the attacker is authenticated to the Symfony application as the victim user. CVSS 4.0 rates confidentiality and integrity impact at High (VC:H, VI:H), reflecting the full account-takeover consequence.
  • Weakness type: CWE-290 — Authentication Bypass by Spoofing.

Affected software

  • symfony/security-http 7.1.0 through 7.4.11 (inclusive)
  • symfony/security-http 8.0.0 through 8.0.11 (inclusive)

Severity

  • CVSS 4.0: 7.6 (HIGH) — CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N
  • CVSS 3.1: 7.5 (HIGH) — CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N

Mitigation and recommended actions

  • Immediate — upgrade: Update symfony/security-http to 7.4.12 or 8.0.12 (or any later release). The fix requires framework.trusted_hosts to be configured before Cas2Handler will operate, and throws a LogicException at startup if it is not set, preventing silent misconfiguration.
  • Workaround (if immediate patching is not possible): Explicitly configure trusted hosts in your Symfony application to prevent Host header spoofing: 
    # config/packages/framework.yaml
framework:
    trusted_hosts: ['your-domain.example.com', '^www.example.com$']

    Alternatively, call Request::setTrustedHosts([...]) early in your application bootstrap. This causes Symfony’s HttpFoundation layer to reject requests with unrecognized Host headers before the CAS service URL is constructed.

  • Additional hardening: Review all internet-exposed Symfony applications using CAS SSO and confirm that framework.trusted_hosts is configured, regardless of patching status.

IONIX Status

The IONIX research team is tracking ongoing exploitation attempts and recommends immediate patching. Potentially affected assets are outlined in this post.

References

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