CVE-2026-16728
published 2026-07-29CVE-2026-16728: undici's retry interceptor can deliver a response whose body length does not match the Content-Length header exposed to the application after a retry or resume…
PriorityP431medium6.5CVSS 3.1
AVNACLPRNUINSUCNILAL
EPSS
0.18%
7.2th percentile
undici's retry interceptor can deliver a response whose body length does not match the Content-Length header exposed to the application after a retry or resume of a partial response. In undici before 6.28.0, from 7.0.0 up to before 7.29.0, and from 8.0.0 up to before 8.9.0, a malicious or faulty upstream can return a partial response with a mismatched framing header, close the socket early, and have the retry interceptor assemble a body of a different length while the original Content-Length stays attached. Applications that use the retry interceptor and forward upstream headers and bodies downstream, such as proxies or gateways, may then emit an invalid HTTP response with a stale Content-Length, leading to downstream response desynchronization, connection hangs, or response corruption. Exploitation requires the retry interceptor enabled, an upstream returning a mismatched partial response, and a downstream forwarder that does not remove or recalculate Content-Length. The issue is fixed in undici 6.28.0, 7.29.0, and 8.9.0.
Affected
9 ranges
| Vendor | Product | Version range | Fixed in |
|---|---|---|---|
| nodejs | undici | < 6.28.0 | 6.28.0 |
| nodejs | undici | >= 7.0.0 < 7.29.0 | 7.29.0 |
| nodejs | undici | >= 8.0.0 < 8.9.0 | 8.9.0 |
| undici | undici | < 6.28.0 | 6.28.0 |
| undici | undici | >= 0 < 6.28.0 | 6.28.0 |
| undici | undici | >= 7.0.0 < 7.29.0 | 7.29.0 |
| undici | undici | >= 7.0.0 < 7.29.0 | 7.29.0 |
| undici | undici | >= 8.0.0 < 8.9.0 | 8.9.0 |
| undici | undici | >= 8.0.0 < 8.9.0 | 8.9.0 |
CVSS provenance
nvdv3.16.5MEDIUMCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L
vendor_redhat6.5MEDIUM
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GHSA
undici vulnerable to downstream response desynchronization via retry interceptor
ghsa·2026-08-03
CVE-2026-16728 [MEDIUM] CWE-444 undici vulnerable to downstream response desynchronization via retry interceptor
undici vulnerable to downstream response desynchronization via retry interceptor
### Impact
Undici's `interceptors.retry()` can deliver a response whose body length does not match the `Content-Length` header exposed to the application after a retry or resume of a partial response. Applications that use `interceptors.retry()` and forward upstream response headers and bodies downstream, for example proxy or gateway applications, may emit an invalid HTTP response with a stale `Content-Length` header. This can lead to downstream response desynchronization, connection hangs, or response corruption in clients or intermediaries that rely on the forwarded framing metadata.
A malicious or faulty upstream can respond to a range request with a `206 Partial Content` response such as:
```http
Conte
VulDB
nodejs undici up to 6.27.x/7.28.x/8.8.x Retry Interceptor improper synchronization
vuldb·2026-07-29·CVSS 4.8
CVE-2026-16728 [MEDIUM] nodejs undici up to 6.27.x/7.28.x/8.8.x Retry Interceptor improper synchronization
A vulnerability, which was classified as critical, has been found in nodejs undici up to 6.27.x/7.28.x/8.8.x. This affects an unknown part of the component Retry Interceptor. The manipulation leads to improper synchronization.
This vulnerability is uniquely identified as CVE-2026-16728. The attack is possible to be carried out remotely. No exploit exists.
It is advisable to upgrade the affected component.
Red Hat
undici: undici: Response desynchronization via retry interceptor with mismatched Content-Length
vendor_redhat·2026-07-29·CVSS 6.5
CVE-2026-16728 [MEDIUM] CWE-444 undici: undici: Response desynchronization via retry interceptor with mismatched Content-Length
undici: undici: Response desynchronization via retry interceptor with mismatched Content-Length
undici's retry interceptor can deliver a response whose body length does not match the Content-Length header exposed to the application after a retry or resume of a partial response. In undici before 6.28.0, from 7.0.0 up to before 7.29.0, and from 8.0.0 up to before 8.9.0, a malicious or faulty upstream can return a partial response with a mismatched framing header, close the socket early, and have the retry interceptor assemble a body of a different length while the original Content-Length stays attached. Applications that use the retry interceptor and forward upstream headers and bodies downstream, such as proxies or gateways, may then emit an invalid HTTP response with a stale Content-Lengt
No detection rules found.
No public exploits indexed.
No writeups or analysis indexed.
2026-07-29
Published