Arbitrary Code Injection Affecting elysia package, versions <1.4.17
Threat Intelligence
Snyk has a proof-of-concept or detailed explanation of how to exploit this vulnerability.
The probability is the direct output of the EPSS model, and conveys an overall sense of the threat of exploitation in the wild. The percentile measures the EPSS probability relative to all known EPSS scores. Note: This data is updated daily, relying on the latest available EPSS model version. Check out the EPSS documentation for more details.
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Start learning- Snyk IDSNYK-JS-ELYSIA-14287466
- published10 Dec 2025
- disclosed9 Dec 2025
- creditsportshead
Introduced: 9 Dec 2025
NewCVE-2025-66457 (opens in a new tab)How to fix?
Upgrade elysia to version 1.4.17 or higher.
Overview
elysia is an Ergonomic Framework for Human
Affected versions of this package are vulnerable to Arbitrary Code Injection via the cookie config. An attacker can execute arbitrary code by injecting malicious input into the configuration when dynamic cookies are enabled and the cookie schema is provisioned by the environment.
Note: This is only exploitable if an attacker has write access to the cookie configuration.
Workaround
This vulnerability can be mitigated by sanitizing cookie-related input from the environment before it is used.
PoC
new Elysia({
cookie: {
secrets: `' + console.log('pwned from secrets') + '`
},
})
.get("/", () => "hello world", {
cookie: t.Cookie({
foo: t.Any(),
}),
})