[dependabot]

Bumps undici from 6.24.0 to 6.27.0.

Release notes

Sourced from undici's releases.

v6.27.0

⚠️ Security Release

This release line addresses 4 security advisories.

Action required: Upgrade to undici 6.27.0 or later.

npm install undici@^6.27.0

Note on patched version: the v6 fixes shipped in v6.27.0, not 6.26.0 — v6.26.0 contains only the chunked-EOF fix (#5308) and the version bump, none of the security fixes below.

The v6 line is not affected by the SOCKS5 advisories (GHSA-vmh5-mc38-953g, GHSA-hm92-r4w5-c3mj), the shared-cache disclosure (GHSA-pr7r-676h-xcf6), or the 8.x-only WebSocket regression (GHSA-38rv-x7px-6hhq).

Summary

Advisory	CVE	Severity (CVSS)	Fixed in	Fix commit
GHSA-vxpw-j846-p89q	CVE-2026-12151	High (7.5)	6.27.0	b7f252e7
GHSA-p88m-4jfj-68fv	CVE-2026-9679	Moderate (5.9)	6.27.0	25efa447
GHSA-g8m3-5g58-fq7m	CVE-2026-11525	Low (3.7)	6.27.0	25efa447
GHSA-35p6-xmwp-9g52	CVE-2026-6733	Low (3.7)	6.27.0	f4c31d60

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High severity

WebSocket DoS via fragment count bypass — CVE-2026-12151

GHSA-vxpw-j846-p89q · CWE-400, CWE-770 Fix: b7f252e7 Backport WebSocket maxPayloadSize fixes (#5423, backported to v6 in #5428)

A malicious WebSocket server can stream a large number of small or empty continuation frames. Undici enforced a limit on cumulative payload size but did not limit the number of fragments per message, leading to unbounded memory growth and denial of service. All releases from 6.17.0 onward are affected.

• Affected: applications using new WebSocket(...) or WebSocketStream against untrusted endpoints.
• Workaround: none — upgrade is required.

---

Moderate severity

HTTP header injection via Set-Cookie percent-decoding — CVE-2026-9679

... (truncated)

Commits

• 551138c Bumped v6.27.0 (#5431)
• b7f252e Backport WebSocket maxPayloadSize fixes to v7.x (#5423) (#5428)
• 25efa44 fix(cookies): preserve values and parse SameSite strictly
• f4c31d6 fix: guard idle socket validation to skip fresh sockets (#5400)
• 768beac Bumped v6.26.0 (#5323)
• 7917b25 fix: validate EOF for chunked h1 responses (#5308)
• 3420499 Bumped v6.25.0 (#5029)
• d7a1e55 feat: add configurable maxPayloadSize for WebSocket (#4955)
• a9d1848 Do not mark v6.x releases as latest
• 0126586 Ignore local agent configuration files
• Additional commits viewable in compare view

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