Summary
Symfony's Cas2Handler Derives CAS service URL from Client Host Header → Cross-Service Ticket Replay
Cas2Handler builds this service parameter from Request::getSchemeAndHttpHost(), which reflects the attacker-controlled HTTP Host header whenever Symfony's framework.trusted_hosts setting is not configured (the default). An attacker who controls any other application registered with the same CAS server can replay a victim's ticket against the Symfony application, with a spoofed Host header, and be authenticated as that victim.
Resolution
A new required service_url configuration option is introduced on Cas2Handler. The CAS service parameter sent to the validation endpoint is now built from this configured URL instead of being derived from the request's Host header, preventing cross-service ticket replay via Host header spoofing.
The patch for this issue is available here for branch 7.4.
Credits
Symfony would like to thank Claude Mythos Preview (via Project Glasswing) for reporting the issue and Nicolas Grekas for providing the fix.
Impact
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
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symfony/security-http to 7.4.12 or later; symfony/security-http to 8.0.12 or later; symfony/symfony to 7.4.12 or later; symfony/symfony to 8.0.12 or later
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Frequently Asked Questions
- What is CVE-2026-45074? CVE-2026-45074 is a medium-severity security vulnerability in symfony/security-http (composer), affecting versions >= 7.1.0, < 7.4.12. It is fixed in 7.4.12, 8.0.12.
- Which packages are affected by CVE-2026-45074?
symfony/security-http(composer) (versions >= 7.1.0, < 7.4.12)symfony/symfony(composer) (versions >= 7.1.0, < 7.4.12)
- Is there a fix for CVE-2026-45074? Yes. CVE-2026-45074 is fixed in 7.4.12, 8.0.12. Upgrade to this version or later.
- Is CVE-2026-45074 exploitable, and should I be worried? Whether CVE-2026-45074 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2026-45074 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2026-45074?
- Upgrade
symfony/security-httpto 7.4.12 or later - Upgrade
symfony/security-httpto 8.0.12 or later - Upgrade
symfony/symfonyto 7.4.12 or later - Upgrade
symfony/symfonyto 8.0.12 or later
- Upgrade