GHSA-r5rp-j6wh-rvv4 Hono: Non-breaking space prefix bypass in cookie name handling in getCookie()

• npm hono: < 4.12.12 → fixed in 4.12.12

Summary A discrepancy between browser cookie parsing and `parse()` handling allows cookie prefix protections to be bypassed. Cookie names that are treated as distinct by the browser may be normalized to the same key by `parse()`, allowing attacker-controlled cookies to override legitimate ones. Details Browsers follow RFC 6265bis and only trim SP (`0x20`) and HTAB (`0x09`) from cookie names. Other characters, such as the non-breaking space (`U+00A0`), are preserved as part of the cookie name. For example, the browser treats the following cookies as distinct: ``` "dummy-cookie" "\u00a0dummy-cookie" ``` However, `parse()` previously used JavaScript's `trim()`, which removes a broader set of characters including `U+00A0`. As a result, both names are normalized to: ``` "dummy-cookie" ``` This mismatch allows attacker-controlled cookies with a `U+00A0` prefix to shadow or override legitimate cookies when accessed via `getCookie()`. Impact An attacker who can set cookies (e.g., via a man-in-the-middle on a non-secure page or other injection vector) can bypass cookie prefix protections and override sensitive cookies. This may lead to: • Bypassing `__Secure-` and `__Host-` prefix protections • Overriding cookies that rely on the Secure attribute • Session fixation or session hijacking depending on application usage This issue affects applications that rely on `getCookie()` for security-sensitive cookie handling.