Elysia affected by arbitrary code injection through cookie config

CISA KEV is observed exploitation evidence. FIRST EPSS is a dated prediction of exploitation in the next 30 days. Missing scores are unknown. This collector requests predictions only for explicit CVE aliases in the public NuGet archive; Microsoft release views retain their existing prediction scope.

No collected risk observation for these identifiers. This does not establish absence of exploitation or a zero probability.

Elysia is a Typescript framework for request validation, type inference, OpenAPI documentation and client-server communication. Versions 1.4.17 and below are subject to arbitrary code execution from cookie config. When dynamic cookies are enabled (e.g. there an existing cookie schema), the cookie config is injected into the compiled route without first being sanitised. Availability of this exploit is generally low, but when combined with GHSA-hxj9-33pp-j2cc, it allows for a full RCE chain. An attack requires write access to either the Elysia app's source code (in which case the vulnerability is meaningless) or write access to the cookie config (perhaps where it is assumed to be provisioned by the environment). This issue is fixed in version 1.4.18.

Source published

9 Dec 2025 20:03:45 UTC

Source modified

12 Dec 2025 19:39:02 UTC

Observed here

23 Oct 2026 15:48:27 UTC

Source terms

CVE Program Terms of Use

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This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: cve-program · CVE Program Terms of Use. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS 4.0 · 7.5 CVSS:4.0/AV:N/AC:L/AT:P/PR:H/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N

Elysia is a Typescript framework for request validation, type inference, OpenAPI documentation and client-server communication. Versions 1.4.17 and below are subject to arbitrary code execution from cookie config. When dynamic cookies are enabled (e.g. there an existing cookie schema), the cookie config is injected into the compiled route without first being sanitised. Availability of this exploit is generally low, but when combined with GHSA-hxj9-33pp-j2cc, it allows for a full RCE chain. An attack requires write access to either the Elysia app's source code (in which case the vulnerability is meaningless) or write access to the cookie config (perhaps where it is assumed to be provisioned by the environment). This issue is fixed in version 1.4.18.

Source published

Dec 9, 2025, 8:03:45 PM (timezone not stated)

Source modified

Dec 12, 2025, 7:39:02 PM (timezone not stated)

Observed here

9 Nov 2026 06:02:50 UTC

Source terms

ENISA EUVD · source terms and attribution apply

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This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: euvd · ENISA EUVD · source terms and attribution apply. Source text is retained; field grouping and change labels are provided by ChangeIntel.

EUVD CVSS 4.0 · 7.5 CVSS:4.0/AV:N/AC:L/AT:P/PR:H/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N

Elysia is a Typescript framework for request validation, type inference, OpenAPI documentation and client-server communication. Versions 1.4.17 and below are subject to arbitrary code execution from cookie config. When dynamic cookies are enabled (e.g. there an existing cookie schema), the cookie config is injected into the compiled route without first being sanitised. Availability of this exploit is generally low, but when combined with GHSA-hxj9-33pp-j2cc, it allows for a full RCE chain. An attack requires write access to either the Elysia app's source code (in which case the vulnerability is meaningless) or write access to the cookie config (perhaps where it is assumed to be provisioned by the environment). This issue is fixed in version 1.4.18.

Source published

9 Dec 2025 20:15:54 UTC

Source modified

14 Oct 2026 21:10:00 UTC

Observed here

25 Oct 2026 03:17:36 UTC

Source terms

NIST NVD usage terms; underlying source attribution retained

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This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: nvd · NIST NVD usage terms; underlying source attribution retained. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS 4.0 · [email protected] · Secondary · 7.5 CVSS:4.0/AV:N/AC:L/AT:P/PR:H/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

CVSS 3.1 · [email protected] · Primary · 8.8 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H

Arbitrary code execution from cookie config. If dynamic cookies are enabled (ie there exists a schema for cookies), the cookie config is injected into the compiled route without first being sanitised. Availability of this exploit is generally low, as it requires write access to either the Elysia app's source code (in which case the vulnerability is meaningless) or write access to the cookie config (perhaps where it is assumed to be provisioned by the environment). However when combined with GHSA-hxj9-33pp-j2cc, this vulnerability allows for a full RCE chain. ### Impact - aot enabled (default) - cookie schema passed to route - Cookie config controllable eg. via env Example of vulnerable code ```js new Elysia({ cookie: { secrets: `' + console.log('pwned from secrets') + '` }, }) .get("/", () => "hello world", { cookie: t.Cookie({ foo: t.Any(), }), }) ``` POC: https://github.com/sportshead/elysia-poc ### Patches Patched by 1.4.17 (https://github.com/elysiajs/elysia/pull/1564) Reference commit: - https://github.com/elysiajs/elysia/pull/1564/commits/26935bf76ebc43b4a43d48b173fc853de43bb51e - https://github.com/elysiajs/elysia/pull/1564/commits/3af978663e437dccc6c1a2a3aff4b74e1574849e ### Workarounds Sanitize cookie-related env input ```typescript const overrideUnsafeQuote = (value: string) => // '`' + value + '`' '`' + value.replace(/'/g, '\\`').replace(/\${/g, '$\\{') + '`' ```

Source published

9 Dec 2025 17:12:05 UTC

Source modified

4 Feb 2026 03:09:32 UTC

Observed here

24 Oct 2026 13:17:17 UTC

Source terms

GitHub Advisory Database · CC-BY-4.0

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This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: osv · GitHub Advisory Database · CC-BY-4.0. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS_V4 · CVSS:4.0/AV:N/AC:L/AT:P/PR:H/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N

Publisher rating · HIGH