Effect: Cookie attribute injection via domain, path, and name fields in @effect/platform makeCookie()

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS 4.0

6.3 · CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:L/VA:N/SC:L/SI:L/SA:N · score source

EPSS

• CVE-2026-115779: 0.63% estimated exploitation activity in the next 30 days; percentile 50.40 (FIRST EPSS, 2026-11-10). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Impact The `name`, `domain`, and `path` fields of `makeCookie()` were validated with a regex that allows `;`, the attribute separator in `Set-Cookie` headers. Because `serializeCookie()` writes those fields verbatim, a caller who passes untrusted input into any of them can append arbitrary attributes to the header. For example, a `domain` of `"legit.com; Domain=.parent.tld"` serializes to `session=token; Domain=legit.com; Domain=.parent.tld`. RFC 6265 §5.3 takes the last occurrence, so the injected domain wins and the cookie widens to the parent domain. The same trick sets `SameSite=None` or `Max-Age` when the caller has not set those options itself. The `value` field is unaffected: it passes through `encodeURIComponent`, which encodes `;`. CR and LF are rejected by the existing regex, so header splitting is not possible.

Patches Fixed in #6763 (v4) and #6765 (v3): the shared regex is split into per-field validators that reject `;`, and `serializeCookie()` now validates…

Published by the source

10 Nov 2026, 15:57 UTC

Last modified by the source

10 Nov 2026, 16:15 UTC

Source last checked

11 Nov 2026, 06:15 UTC

1. Revision 2 · amended · 11 Nov 2026

   Amended from osv record GHSA-chp3-j5qr-2vfr

2. Revision 1 · created · 10 Nov 2026

   Published from ghsa record GHSA-chp3-j5qr-2vfr

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# Patch Next advisory brief: CVE-2026-115779

Advisory: Effect: Cookie attribute injection via domain, path, and name fields in @effect/platform makeCookie()
IDs: CVE-2026-115779, GHSA-chp3-j5qr-2vfr
Record: https://patchnext.com/advisories/cve-2026-115779 (revision 2, source checked 11 Nov 2026, 06:15 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 6.3)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: @effect/platform 0.97.1; effect 4.0.0-beta.103. A vendor fix does not mean a deployment is fixed.

## Affected components
- npm @effect/platform: affected >= 0.1.0, < 0.97.1; fixed in 0.97.1
- npm effect: affected >= 4.0.0-beta.0, < 4.0.0-beta.103; fixed in 4.0.0-beta.103

## Suggested inspection (read-only)
- `npm ls @effect/platform --all`: lists every installed copy and version, including transitive ones. Run in the project root after `npm ci`.
- `npm ls effect --all`: lists every installed copy and version, including transitive ones. Run in the project root after `npm ci`.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on @effect/platform, effect.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-chp3-j5qr-2vfr (GitHub-reviewed advisory GHSA-chp3-j5qr-2vfr lists affected ranges: npm @effect/platform >=0.1.0 =4.0.0-beta.0 <4.0.0-beta.103)
- Verified: https://osv.dev/vulnerability/GHSA-chp3-j5qr-2vfr (OSV record GHSA-chp3-j5qr-2vfr lists affected ranges: npm @effect/platform >=0.1.0 =4.0.0-beta.0 <4.0.0-beta.103 (fixed))

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