undici vulnerable to Subresource Integrity bypass via whitespace in integrity metadata

published 2026-11-06 3d ago modified 2026-11-06 3d ago also EUVD-2026-118182

cvss: 5.9; version 3.1, CNA
cisa kev: Not listed; not in CISA's catalog
epss: 0.1%; EPSS 0.1% chance of exploitation in 30 days, percentile 2%
public exploits: 0; none known

undici is an HTTP client for Node.js. In versions 7.15.0 through 7.30.1 and 8.0.0 through 8.12.3, fetch verifies Subresource Integrity metadata by splitting the integrity string on a single space, but the SRI grammar separates metadata by ASCII whitespace, which also includes the horizontal tab. An integrity value whose digest is preceded by a tab or other ASCII whitespace is parsed as a single unrecognized token and skipped, and when no recognized algorithm remains undici treats the integrity list as empty and accepts the response, so a server returning a body different from the pinned digest passes the check. An application that pins a response with a valid but whitespace-surrounded SRI value receives attacker-controlled bytes with no integrity error, and the attacker needs only to control the response body, not the integrity metadata. The issue is fixed in undici 7.30.2 and 8.12.4, and users should upgrade to one of those versions or later. As a workaround, supply SRI integrity metadata without surrounding whitespace, using a single space to separate multiple digests.

Patch / fix

fixed in 1

undici undici 7.30.2, 8.12.4

Is CVE-2026-120423 in your stack? Fencer shows which of your repositories are affected as soon as an advisory lands, and opens the fix as a pull request.

Check with Fencer

Exploit prediction

0.13% chance of exploitation in the next 30 days, higher than 2% of all scored CVEs (FIRST EPSS, 2026-11-09).

CVSS scores

assigned by	version	score	vector
CNA	3.1	5.9	CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N

Affected products

undici undici

Classification

Weakness

CWE-354 Improper Validation of Integrity Check Value

References

Sources

CVE List CVE-2026-120423
NVD CVE-2026-120423

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.