vulnerability / NVI-00013778 / Revision 1
Hono: Incomplete fix for CVE-2026-39408: `toSSG()` still writes files outside the output directory
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01 / Meaning
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6.5 medium
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As of · GitHub Advisory Database
02 / Applicability
The affected context
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hono
source listed< 4.13.5
### Summary The fix released for CVE-2026-39408 does not cover every traversal sequence. `toSSG()` can still write files outside the configured output directory when a route parameter contains consecutive parent-directory segments. ### Details Static site generation builds each output path from the route path and the values supplied through `ssgParams`, then verifies that the result stays inside the output directory. That check normalizes the path with the same routine that built it, and the routine did not fully collapse runs of consecutive parent-directory segments. A value carrying enough of them produces a path the check accepts, but the filesystem resolves outside the output directory. The earlier fix handled a single parent-directory segment, so it blocks the sequence reported at the time while leaving longer runs unhandled. The check also treated output directories that differ only in how they are rooted as equivalent. This arises when an application generates a static site from route parameter values it does not fully control — slugs coming from a CMS, an API, or user submissions. ### Impact A value reaching `ssgParams` from an untrusted source can cause build output
03 / Response
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04 / Limits
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05 / Provenance
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- GHSA-gqvv-2mrq-wpjv ↗
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- Revision 1 ·
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