CVE-2026-16728: undici vulnerable to downstream response desynchronization via retry interceptor
Affects undiciSource GCVE Database
Not known to be exploited · CVSS 4.8 Medium : upgrade to 6.28.0 when convenient.
Data as of 1 Nov 2026, 22:58 UTC
- EPSS
- 0.2% chance of exploitation in 30 days – higher than 21% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
- Patch
- Available – fixed in 6.28.0, 7.29.0, 8.9.0
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:NExploitation evidence
Disclosed: evidence found.
CVE published 3 Aug 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 1 Nov 2026.
What to do
Upgrade undici to 6.28.0; undici to 7.29.0; undici to 8.9.0.
Affected software
| Product | Affected | Fixed in |
|---|---|---|
| npmundici | Affected
| Fixed in
|
| npmundici | Affected
| Fixed in
|
| npmundici | Affected
| Fixed in
|
Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.
AI-suggested
A fix is available in undici versions 6.28.0, 7.29.0, and 8.9.0 and later; users should upgrade to these versions or newer. As workarounds, disable interceptors.retry() when dealing with untrusted upstream servers, or ensure that Content-Length headers are removed or recalculated before forwarding responses assembled or transformed by undici.
Description
Undici versions prior to 6.28.0, 7.29.0, and 8.9.0 contain a vulnerability in the interceptors.retry() feature where the response body length may not match the Content-Length header after retrying or resuming a partial response. This mismatch can cause downstream response desynchronization, connection hangs, or response corruption in clients or intermediaries that rely on the Content-Length header for framing. The issue arises when an upstream server returns a partial content response with incorrect Content-Length, and the retry interceptor retries the request, resulting in a stale Content-Length header being forwarded. The vulnerability is patched in undici versions 6.28.0, 7.29.0, and 8.9.0 and later.
References
- github.com/nodejs/undici/security/advisories/GHSA-8xcm-r25x-g524 (opens in a new tab)
- nvd.nist.gov/vuln/detail/CVE-2026-16728 (opens in a new tab)
- github.com/nodejs/undici/commit/1b5a5312c3a7d7a30c31bf0d000b39a8a2531e1c (opens in a new tab)
- github.com/nodejs/undici/commit/2b3f749336d356bbbc50192f87f6cf7bc714721a (opens in a new tab)
- github.com/nodejs/undici/commit/4a9dafb16ff43880cf590e6d9c2aeee25fbff6d7 (opens in a new tab)
- github.com/nodejs/undici/commit/4fd5a0c61e627f928b7003adc4ffe1e55ec63420 (opens in a new tab)
- github.com/nodejs/undici/commit/cba3a52ac2e7abcc4e656d82af8579ea82c2bb9e (opens in a new tab)
- github.com/nodejs/undici/commit/e11a68ed4ff345c79402476f7a00d473443e318d (opens in a new tab)
- hackerone.com/reports/3828685 (opens in a new tab)
- cna.openjsf.org/security-advisories.html (opens in a new tab)
- github.com/nodejs/undici (opens in a new tab)
- github.com/nodejs/undici/releases/tag/v6.28.0 (opens in a new tab)
- github.com/nodejs/undici/releases/tag/v7.29.0 (opens in a new tab)
- github.com/nodejs/undici/releases/tag/v8.9.0 (opens in a new tab)