vulnerability / NVI-00016302 / Revision 1
hono: AWS Lambda adapter merges multiple `Set-Cookie` headers into one value, dropping cookies on ALB single-header and Lattice
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01 / Meaning
Why it matters
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5.3 medium
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As of · GitHub Advisory Database
02 / Applicability
The affected context
Affected versions, configuration prerequisites and known exclusions are public. Confirm each one against the deployed service.
hono
source listed< 4.12.25
### Summary On AWS Lambda, the ALB single-header response and the VPC Lattice v2 response join multiple `Set-Cookie` headers into one comma-separated value. Because commas also appear inside cookie attributes (for example `Expires` dates), clients cannot split the value back into individual cookies and silently drop or misparse them. ### Details Per RFC 6265, each cookie must be its own `Set-Cookie` header line, and commas may appear inside attribute values. Joining cookies with `", "` collides with those commas, producing a value that clients cannot reliably split. Only ALB single-header mode and VPC Lattice v2 are affected; API Gateway v1/v2 and ALB with multi-value headers enabled already use an array and are unaffected. ### Impact A client may receive only one of the cookies, a malformed cookie, or none. Session, CSRF, or preference cookies can silently fail to apply, breaking sessions or forcing re-authentication. This affects applications that set multiple cookies per response and run on AWS Lambda behind an ALB in single-header mode (the default) or VPC Lattice v2.
03 / Response
What to do next
- investigate
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04 / Limits
What this report cannot establish
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05 / Provenance
Sources you can inspect
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- GHSA-j6c9-x7qj-28xf ↗
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Public revision history
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- Revision 1 ·
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