Summary
Symfony possible session fixation vulnerability
Description
SessionStrategyListener does not always migrate the session after a successful login. It only migrate the session when the logged-in user identifier changes. In some use cases, the user identifier doesn't change between the verification phase and the successful login, while the token itself changes from one type (partially-authenticated) to another (fully-authenticated). When this happens, the session id should be regenerated to prevent possible session fixations.
Resolution
Symfony now checks the type of the token in addition to the user identifier before deciding whether the session id should be regenerated.
The patch for this issue is available here for branch 5.4.
Credits
We would like to thank Robert Meijers for reporting the issue and providing the fix.
Impact
CVE-2023-46733 has a CVSS score of 6.5 (Medium). The vector is network-reachable, low privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (5.4.31, 6.3.8); upgrading removes the vulnerable code path.
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 5.4.31 or later; symfony/security-http to 6.3.8 or later; symfony/symfony to 5.4.31 or later; symfony/symfony to 6.3.8 or later
Kodem Kai can prioritize this vulnerability in your dependency tree and generate a fix recommendation.
Frequently Asked Questions
- What is CVE-2023-46733? CVE-2023-46733 is a medium-severity security vulnerability in symfony/security-http (composer), affecting versions >= 5.4.21, < 5.4.31. It is fixed in 5.4.31, 6.3.8.
- How severe is CVE-2023-46733? CVE-2023-46733 has a CVSS score of 6.5 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
- Which packages are affected by CVE-2023-46733?
symfony/security-http(composer) (versions >= 5.4.21, < 5.4.31)symfony/symfony(composer) (versions >= 5.4.21, < 5.4.31)
- Is there a fix for CVE-2023-46733? Yes. CVE-2023-46733 is fixed in 5.4.31, 6.3.8. Upgrade to this version or later.
- Is CVE-2023-46733 exploitable, and should I be worried? Whether CVE-2023-46733 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-2023-46733 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-2023-46733?
- Upgrade
symfony/security-httpto 5.4.31 or later - Upgrade
symfony/security-httpto 6.3.8 or later - Upgrade
symfony/symfonyto 5.4.31 or later - Upgrade
symfony/symfonyto 6.3.8 or later
- Upgrade