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Findings

CVE-2026-109841

undici is an HTTP client library for Node.js.

Published Oct 15, 2026 · corrected/updated Oct 15, 2026 · evidence confidence high

undici is an HTTP client library for Node.js. In versions 7.15.0 through 7.30.0 and 8.0.0 through 8.12.1, its fetch() implementation verifies Subresource Integrity metadata by matching the algorithm token against a lowercase-only set, even though the SRI specification defines the token by its ASCII-lowercase form, so a valid but non-lowercase token such as an uppercase or mixed-case SHA256 is treated as unknown and skipped. When no recognized algorithm remains, undici treats the integrity list as empty and accepts the response, so a server returning a body that does not match the pinned digest passes the check. An attacker who controls only the response body can therefore deliver attacker-controlled bytes to an application that pinned a valid uppercase or mixed-case SRI token, with no integrity error, affecting response integrity only. The issue is fixed in undici 7.30.1 and 8.12.2, which normalize the algorithm token to ASCII lowercase before validation, and users should upgrade to one of those versions or later. As a workaround, use lowercase algorithm tokens such as sha256, sha384, or sha512 in integrity metadata.

Grounded briefings

Catalog interpretations for three audiences. Each brief cites ingested metadata and the original advisories below. They are not independent research and they do not invent exploit steps.

Executive

CVE-2026-109841 is a medium public vulnerability record for this product. It is not currently listed in the CISA Known Exploited catalog. Check the linked vendor or CERT advisories for patch status. This summary is a catalog interpretation of the ingested metadata and cites the original advisories below.

System administrator

Identify whether this product is in your estate, then compare installed versions with the affected ranges. Affected packages or ranges on record: node-undici (5.15.0+dfsg1+~cs20.10.9.3-1, 5.15.0+dfsg1+~cs20.10.9.3-1+deb12u1, 5.15.0+dfsg1+~cs20.10.9.3-1+deb12u2); node-undici (7.15.0+dfsg+~cs3.2.0-1, 7.15.0+dfsg+~cs3.2.0-3, 7.16.0+dfsg+~cs3.2.0-1); node-undici (7.15.0+dfsg+~cs3.2.0-1, 7.15.0+dfsg+~cs3.2.0-3, 7.16.0+dfsg+~cs3.2.0-1). Check the linked vendor or CERT advisories for patch status. Prefer the vendor or distribution advisory linked in Sources before changing production systems. This is a catalog interpretation, not a runbook.

Security analyst

Signals on file: CVSS 5.9, EPSS 0.3%. It is not currently listed in the CISA Known Exploited catalog. Weakness classes: CWE-178. Sources contributing to this record: cve_org, epss, nvd, osv. Public exploit references, when present, are outbound links only and are not proof of active exploitation. This is a catalog interpretation of stored metadata.

Exploitation and remediation

  • Exploitation evidence

    Not listed as known exploited in CISA KEV. Not in the CISA KEV catalog.

  • Patch and remediation

    No required-action text is stored yet. Use the vendor or CERT links in Sources for patch availability.

  • Safe detection guidance

    Compare installed versions with the affected ranges below and verify the advisory from the original publisher. This site stores metadata and outbound links only; it does not ship exploit code or proof-of-concept payloads.

Technology hubs

Debian

Code

The project this record applies to. Exploit listings stay in References.

Timeline

Detection, updates, and resolution for this record.

  1. Oct 15, 2026 · NIST NVD

    Detected

    undici is an HTTP client library for Node.js. In versions 7.15.0 through 7.30.0 and 8.0.0 through 8.12.1, its fetch() implementation verifies Subresource Integrity metadata by matching the algorithm token against a lowercase-only set, even though the SRI specification defines the token by its ASCII-lowercase form, so a valid but non-lowercase token such as an uppercase or mixed-case SHA256 is trea

  2. Oct 15, 2026 · OSV.dev

    Updated

    undici is an HTTP client library for Node.js. In versions 7.15.0 through 7.30.0 and 8.0.0 through 8.12.1, its fetch() implementation verifies Subresource Integrity metadata by matching the algorithm token against a lowercase-only set, even though the SRI specification defines the token by its ASCII-lowercase form, so a valid but non-lowercase token such as an uppercase or mixed-case SHA256 is trea

Affected

  • Debian:12 node-undici5.15.0+dfsg1+~cs20.10.9.3-1, 5.15.0+dfsg1+~cs20.10.9.3-1+deb12u1, 5.15.0+dfsg1+~cs20.10.9.3-1+deb12u2
  • Debian:13 node-undici7.15.0+dfsg+~cs3.2.0-1, 7.15.0+dfsg+~cs3.2.0-3, 7.16.0+dfsg+~cs3.2.0-1
  • Debian:14 node-undici7.15.0+dfsg+~cs3.2.0-1, 7.15.0+dfsg+~cs3.2.0-3, 7.16.0+dfsg+~cs3.2.0-1

Sources

  • CVE.orgVulnerability recordCVE-2026-109841

    Official CVE identifier

    cve.org
  • FIRST EPSSExploitation probabilityCVE-2026-109841

    30-day exploitation probability 0.3%

    first.org
  • NIST NVDVulnerability recordCVE-2026-109841

    undici is an HTTP client library for Node.js. In versions 7.15.0 through 7.30.0 and 8.0.0 through 8.12.1, its fetch() implementation verifies Subresource Integrity metadata by matching the algorithm token against a lowercase-only set, even though the SRI specification defines the

    nvd.nist.gov
  • OSV.devPackage advisoryDEBIAN-CVE-2026-109841
    osv.dev

References