{"id":"CVE-2026-16728","aliases":["GHSA-8xcm-r25x-g524"],"title":"undici vulnerable to downstream response desynchronization via retry interceptor","summary":"undici vulnerable to downstream response desynchronization via retry interceptor","severity":"medium","cvss":4.8,"cwe":["CWE-444"],"vendor":"undici","product":"undici","ecosystem":"npm","affected":["undici < 6.28.0","undici >= 7.0.0, < 7.29.0","undici >= 8.0.0, < 8.9.0"],"patched":["undici 6.28.0","undici 7.29.0","undici 8.9.0"],"published":"2026-08-03","updated":"2026-08-03","source":"GHSA","sourceUrl":"https://github.com/advisories/GHSA-8xcm-r25x-g524","references":[{"url":"https://github.com/nodejs/undici/security/advisories/GHSA-8xcm-r25x-g524"},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-16728"},{"url":"https://github.com/nodejs/undici/commit/1b5a5312c3a7d7a30c31bf0d000b39a8a2531e1c"},{"url":"https://github.com/nodejs/undici/commit/2b3f749336d356bbbc50192f87f6cf7bc714721a"},{"url":"https://github.com/nodejs/undici/commit/4a9dafb16ff43880cf590e6d9c2aeee25fbff6d7"},{"url":"https://github.com/nodejs/undici/commit/4fd5a0c61e627f928b7003adc4ffe1e55ec63420"},{"url":"https://github.com/nodejs/undici/commit/cba3a52ac2e7abcc4e656d82af8579ea82c2bb9e"},{"url":"https://github.com/nodejs/undici/commit/e11a68ed4ff345c79402476f7a00d473443e318d"},{"url":"https://hackerone.com/reports/3828685"},{"url":"https://cna.openjsf.org/security-advisories.html"},{"url":"https://github.com/nodejs/undici/releases/tag/v6.28.0"},{"url":"https://github.com/nodejs/undici/releases/tag/v7.29.0"},{"url":"https://github.com/nodejs/undici/releases/tag/v8.9.0"},{"url":"https://github.com/advisories/GHSA-8xcm-r25x-g524"}],"tags":["ghsa","npm"],"epss":0.00176,"epssPercentile":0.07402,"ingestedAt":"2026-08-03T19:29:00.250Z","slug":"CVE-2026-16728","body":"## Overview\n\n### Impact\n\nUndici'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.\n\nA malicious or faulty upstream can respond to a range request with a `206 Partial Content` response such as:\n\n```http\nContent-Range: bytes 0-99/300\nContent-Length: 300\n```\n\nand then send only 99 bytes before closing the socket. `interceptors.retry()` can then retry with `Range: bytes=99-99`, receive the final byte, and deliver a 100-byte body to the application while the response headers still contain `Content-Length: 300` from the first response.\n\nThe bug requires `interceptors.retry()` to be enabled, an upstream that returns a partial response with a mismatched framing header, and a downstream forwarder that does not remove or recalculate `Content-Length`.\n\n### Patches\n\nPatched in undici v6.28.0, v7.29.0, and v8.9.0. Users should upgrade to one of these versions or later.\n\n### Workarounds\n\n- Disable `interceptors.retry()` for untrusted upstreams.\n- Remove or recalculate `Content-Length` before forwarding a response body assembled or transformed by Undici.\n\n## Affected packages\n\n- `undici < 6.28.0`\n- `undici >= 7.0.0, < 7.29.0`\n- `undici >= 8.0.0, < 8.9.0`\n\n## Remediation\n\nUpgrade to a patched release:\n\n- `undici 6.28.0`\n- `undici 7.29.0`\n- `undici 8.9.0`","depth":"sunlit","depthScore":26,"depthScoreParts":{"impact":26.4,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[]}