CVE-2026-18540
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 th…
Impact
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.
Affected packages
| Ecosystem | Package | Affected | Fixed in |
|---|---|---|---|
| npm | undici | < 6.28.1 | 6.28.1 |
Affected products
| Vendor | Product | Affected versions |
|---|---|---|
| Nodejs | Undici | before 6.28.1 from 7.0.0 before 7.29.1 from 8.0.0 before 8.10.2 |
Weakness classification
References
- NVD record
- CVE.org record
- GitHub advisory
- https://github.com/advisories/GHSA-r53p-7pc4-xj5r
- https://github.com/nodejs/undici/security/advisories/GHSA-r53p-7pc4-xj5r
- https://nvd.nist.gov/vuln/detail/CVE-2026-18540
- https://github.com/nodejs/undici/commit/0160a719063fb0a77f4fdf9500b9166b91e14329
- https://github.com/nodejs/undici/commit/cd8af90b38ae33c2838d54a2d629774122effe95
- https://github.com/nodejs/undici/commit/ce31bc824b578008faae5d3350da66c1b5f71548
- https://hackerone.com/reports/3900104
- https://hackerone.com/reports/3900615
- https://cna.openjsf.org/security-advisories.html
- https://github.com/nodejs/undici/releases/tag/v6.28.1
- https://github.com/nodejs/undici/releases/tag/v7.29.1
- https://github.com/nodejs/undici/releases/tag/v8.10.2