CVE-2026-6733

Summary

Impact: Undici's HTTP/1.1 client is vulnerable to response queue poisoning on reused keep-alive sockets. An attacker-controlled upstream server can inject an unsolicited HTTP/1.1 response onto an idle socket after a request completes. When the client dispatches the next request on that socket, it associates the injected response with the new request, causing responses to be delivered to the wrong requests.

This requires an attacker-controlled or compromised upstream HTTP/1.1 server and keep-alive connection reuse.

Patches: Upgrade to undici v6.26.0, v7.28.0 or v8.5.0.

Workarounds: Disable keep-alive connection reuse by setting keepAliveTimeout: 0 on the Client or Pool.

Affected Software

VendorProductVersion RangeStatus
undiciundici0 < 6.26.0affected
undiciundici6.26.0unaffected
undiciundici7.0.0 < 7.28.0affected
undiciundici7.28.0unaffected
undiciundici8.0.0 < 8.5.0affected
undiciundici8.5.0unaffected

Weaknesses

  • CWE-367: CWE-367: Time-of-check Time-of-use (TOCTOU) Race Condition

ADP Enrichment

CISA ADP Vulnrichment

  • SSVC:
  • Exploitation: none
    • Automatable: no
    • Technical Impact: partial

References