Summary
Astro: Authorization bypass from missing path-segment boundary check when stripping the configured base
Astro stripped a configured base path from request pathnames using a string-prefix check that did not verify a path-segment boundary. With base: "/app", a request to /appX/admin was treated as being under the base and resolved internally to the /admin route, while middleware still observed the public pathname /appX/admin. Middleware that authorizes routes by inspecting context.url.pathname could therefore be bypassed.
Affected versions
astro <= 7.2.3.
Workarounds
Upgrade to astro 7.2.4 or later. As a mitigation before upgrading, avoid relying solely on prefix checks of context.url.pathname for authorization, or reject requests whose pathname does not begin with the configured base followed by a path-segment boundary.
Credits
Reported by @Ryoga-exe.
Impact
An unauthenticated remote attacker can bypass pathname-based middleware authorization in applications that:
- Configure a non-root
base. - Protect base-prefixed routes in middleware using
context.url.pathname.
Because routing and middleware resolved different effective pathnames, a request such as /appX/admin (or other single-character extensions like /app2/admin or /app-/admin) reached the protected /admin route without passing the middleware check that guards /app/admin. Astro's authentication guide demonstrates protecting routes in middleware via context.url.pathname, so this is a reasonable and expected pattern.
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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Fixed in astro 7.2.4. Base stripping now requires the pathname to equal the base without its trailing slash, or to be followed by a /, so a prefix that does not end on a path-segment boundary is no longer treated as being under the base. Routing and context.url.pathname now resolve the same pathname.
Frequently Asked Questions
- What is CVE-2026-84376? CVE-2026-84376 is a medium-severity security vulnerability in astro (npm), affecting versions <= 7.2.3. It is fixed in 7.2.4.
- Which versions of astro are affected by CVE-2026-84376? astro (npm) versions <= 7.2.3 is affected.
- Is there a fix for CVE-2026-84376? Yes. CVE-2026-84376 is fixed in 7.2.4. Upgrade to this version or later.
- Is CVE-2026-84376 exploitable, and should I be worried? Whether CVE-2026-84376 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-2026-84376 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-2026-84376? Upgrade
astroto 7.2.4 or later.