CVE-2026-16728

undici vulnerable to downstream response desynchronization via retry interceptor

Published Jul 29, 2026 CVSS 3.1 · 4.8 Medium EPSS < 1% KEV · Not listed
Description
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.

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

Source ID Title
Github GHSA Github GHSA GHSA-8xcm-r25x-g524 undici vulnerable to downstream response desynchronization via retry interceptor
History
Type Values Removed Values Added
First Time appeared Redhat
Redhat hummingbird
CPEs cpe:/a:redhat:hummingbird:1
Vendors & Products Redhat
Redhat hummingbird
References
Metrics threat_severity

None

threat_severity

Moderate

Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Type Values Removed Values Added
First Time appeared Undici
Undici undici
Vendors & Products Undici
Undici undici
Type Values Removed Values Added
Description 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.
Title undici vulnerable to downstream response desynchronization via retry interceptor
Weaknesses CWE-444
References
Metrics cvssV3_1

{'score': 4.8, 'vector': 'CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
openjs
Published
Updated
Jul 30, 2026, 3:18 PM
Reserved
Jul 23, 2026, 4:21 AM
Status
Analyzed
Published
Jul 29, 2026, 9:17 PM
Modified
Aug 4, 2026, 2:06 PM
Severity
Moderate
Public date
Jul 29, 2026, 8:59 PM