Summary
Undici's cookie header not cleared on cross-origin redirect in fetch
Impact
Undici clears Authorization headers on cross-origin redirects, but does not clear Cookie headers. By design, cookie headers are forbidden request headers, disallowing them to be set in RequestInit.headers in browser environments. Since Undici handles headers more liberally than the specification, there was a disconnect from the assumptions the spec made, and Undici's implementation of fetch.
As such this may lead to accidental leakage of cookie to a 3rd-party site or a malicious attacker who can control the redirection target (ie. an open redirector) to leak the cookie to the 3rd party site.
CVE-2023-45143 has a CVSS score of 3.9 (Low). The vector is network-reachable, high privileges required, and user interaction required. 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 (5.26.2); 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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This was patched in e041de359221ebeae04c469e8aff4145764e6d76, which is included in version 5.26.2.
Frequently Asked Questions
- What is CVE-2023-45143? CVE-2023-45143 is a low-severity security vulnerability in undici (npm), affecting versions < 5.26.2. It is fixed in 5.26.2.
- How severe is CVE-2023-45143? CVE-2023-45143 has a CVSS score of 3.9 (Low). 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 versions of undici are affected by CVE-2023-45143? undici (npm) versions < 5.26.2 is affected.
- Is there a fix for CVE-2023-45143? Yes. CVE-2023-45143 is fixed in 5.26.2. Upgrade to this version or later.
- Is CVE-2023-45143 exploitable, and should I be worried? Whether CVE-2023-45143 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-2023-45143 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-2023-45143? Upgrade
undicito 5.26.2 or later.