{"id":"DEBIAN-CVE-2026-18540","details":"undici's retry interceptor can append the body of a ranged retry response to bytes already delivered from an earlier partial response while still presenting the original response's status and headers. This happens when an upstream server delivers part of a body without a trustworthy resume checkpoint, for example a non-success response whose headers were already sent or a partial-content response with an unusable content range, then closes the connection and answers the resumed range request with more bytes. As a result the response body can be longer than the Content-Length that the application observes. An application that relays such a response to a downstream HTTP/1.1 peer without normalizing the framing can emit a body that exceeds the forwarded Content-Length, and the excess bytes can be interpreted as the start of a following response, which enables downstream response splitting or desynchronization. Exploitation requires an attacker-controlled upstream server and an application that forwards the response through a framing-sensitive path. This affects undici versions before 6.28.1, from 7.0.0 up to 7.29.1, and from 8.0.0 up to 8.10.2. Users should upgrade to undici 6.28.1, 7.29.1, or 8.10.2.","modified":"2026-09-17T08:47:31.421077292Z","published":"2026-09-04T18:17:50.020Z","upstream":["CVE-2026-18540"],"references":[{"type":"ADVISORY","url":"https://security-tracker.debian.org/tracker/CVE-2026-18540"}],"affected":[{"package":{"name":"node-undici","ecosystem":"Debian:12","purl":"pkg:deb/debian/node-undici?arch=source&distro=bookworm"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["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","5.15.0+dfsg1+~cs20.10.9.3-1+deb12u3","5.15.0+dfsg1+~cs20.10.9.3-1+deb12u4","5.19.1+dfsg1+~cs20.10.9.5-1","5.19.1+dfsg1+~cs20.10.9.5-2","5.22.1+dfsg1+~cs20.10.10.2-1","5.26.3+dfsg1+~cs23.10.12-1","5.26.3+dfsg1+~cs23.10.12-2","5.26.3+dfsg1+~cs23.10.12-3","5.28.0+dfsg1+~cs23.11.12.3-1","5.28.0+dfsg1+~cs23.11.12.3-2","5.28.2+dfsg1+~cs23.11.12.3-1","5.28.2+dfsg1+~cs23.11.12.3-2","5.28.2+dfsg1+~cs23.11.12.3-3","5.28.2+dfsg1+~cs23.11.12.3-4","5.28.2+dfsg1+~cs23.11.12.3-5","5.28.2+dfsg1+~cs23.11.12.3-6","5.28.4+dfsg1+~cs23.12.11-1","5.28.4+dfsg1+~cs23.12.11-2","7.1.0+dfsg1+~cs24.12.10-1","7.15.0+dfsg+~cs3.2.0-1","7.15.0+dfsg+~cs3.2.0-3","7.16.0+dfsg+~cs3.2.0-1","7.16.0+dfsg+~cs3.2.0-2","7.18.2+dfsg+~cs3.2.0-1","7.2.3+dfsg1+~cs24.12.11-1","7.2.3+dfsg1+~cs24.12.11-2","7.24.5+dfsg+~cs3.2.0-1","7.24.6+dfsg+~cs3.2.0-1","7.24.6+dfsg+~cs3.2.0-2","7.24.6+dfsg+~cs3.2.0-3","7.3.0+dfsg1+~cs24.12.11-1","7.3.0+dfsg1+~cs24.12.11-2","8.10.2+dfsg+~cs3.2.2-1","8.5.0+dfsg+~cs3.2.0-1","8.5.0+dfsg+~cs3.2.0-2","8.5.0+dfsg+~cs3.2.0-3","8.9.0+dfsg+~cs3.2.0-1"],"ecosystem_specific":{"urgency":"not yet assigned"},"database_specific":{"source":"https://storage.googleapis.com/osv-test-debian-osv/debian-cve-osv/DEBIAN-CVE-2026-18540.json"}},{"package":{"name":"node-undici","ecosystem":"Debian:13","purl":"pkg:deb/debian/node-undici?arch=source&distro=trixie"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["7.15.0+dfsg+~cs3.2.0-1","7.15.0+dfsg+~cs3.2.0-3","7.16.0+dfsg+~cs3.2.0-1","7.16.0+dfsg+~cs3.2.0-2","7.18.2+dfsg+~cs3.2.0-1","7.24.5+dfsg+~cs3.2.0-1","7.24.6+dfsg+~cs3.2.0-1","7.24.6+dfsg+~cs3.2.0-2","7.24.6+dfsg+~cs3.2.0-3","7.3.0+dfsg1+~cs24.12.11-1","7.3.0+dfsg1+~cs24.12.11-2","8.10.2+dfsg+~cs3.2.2-1","8.5.0+dfsg+~cs3.2.0-1","8.5.0+dfsg+~cs3.2.0-2","8.5.0+dfsg+~cs3.2.0-3","8.9.0+dfsg+~cs3.2.0-1"],"ecosystem_specific":{"urgency":"not yet assigned"},"database_specific":{"source":"https://storage.googleapis.com/osv-test-debian-osv/debian-cve-osv/DEBIAN-CVE-2026-18540.json"}},{"package":{"name":"node-undici","ecosystem":"Debian:14","purl":"pkg:deb/debian/node-undici?arch=source&distro=forky"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"8.10.2+dfsg+~cs3.2.2-1"}]}],"versions":["7.15.0+dfsg+~cs3.2.0-1","7.15.0+dfsg+~cs3.2.0-3","7.16.0+dfsg+~cs3.2.0-1","7.16.0+dfsg+~cs3.2.0-2","7.18.2+dfsg+~cs3.2.0-1","7.24.5+dfsg+~cs3.2.0-1","7.24.6+dfsg+~cs3.2.0-1","7.24.6+dfsg+~cs3.2.0-2","7.24.6+dfsg+~cs3.2.0-3","7.3.0+dfsg1+~cs24.12.11-1","7.3.0+dfsg1+~cs24.12.11-2","8.5.0+dfsg+~cs3.2.0-1","8.5.0+dfsg+~cs3.2.0-2","8.5.0+dfsg+~cs3.2.0-3","8.9.0+dfsg+~cs3.2.0-1"],"ecosystem_specific":{"urgency":"not yet assigned"},"database_specific":{"source":"https://storage.googleapis.com/osv-test-debian-osv/debian-cve-osv/DEBIAN-CVE-2026-18540.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N"}]}