CVE-2026-18540 (GCVE-0-2026-18540)

Vulnerability from cvelistv5 – Published: 2026-09-04 17:15 – Updated: 2026-09-04 17:50
VLAI
Title
undici vulnerable to downstream response splitting via retry interceptor
Summary
undici's retry interceptor can append the body of a ranged retry response to bytes already delivered from an earlier partial response while still presenting the original response's status and headers. This happens when an upstream server delivers part of a body without a trustworthy resume checkpoint, for example a non-success response whose headers were already sent or a partial-content response with an unusable content range, then closes the connection and answers the resumed range request with more bytes. As a result the response body can be longer than the Content-Length that the application observes. An application that relays such a response to a downstream HTTP/1.1 peer without normalizing the framing can emit a body that exceeds the forwarded Content-Length, and the excess bytes can be interpreted as the start of a following response, which enables downstream response splitting or desynchronization. Exploitation requires an attacker-controlled upstream server and an application that forwards the response through a framing-sensitive path. This affects undici versions before 6.28.1, from 7.0.0 up to 7.29.1, and from 8.0.0 up to 8.10.2. Users should upgrade to undici 6.28.1, 7.29.1, or 8.10.2.
Severity
3.7 (Low)
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N
SSVC
Exploitation: none Automatable: no Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-09-04 17:50 UTC
CWE
  • CWE-444 - Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')
Assigner
openjs CNA under the redhat root
CNA scorecard C 65/100 over 109 records in the last 180 days details
References
Impacted products
Vendor Product Version CPE status
undici undici Affected: 0 , < 6.28.1 (semver)
Unaffected: 6.28.1 (semver)
Affected: 7.0.0 , < 7.29.1 (semver)
Unaffected: 7.29.1 (semver)
Affected: 8.0.0 , < 8.10.2 (semver)
Unaffected: 8.10.2 (semver)
guessed Create a notification for this product.
Credits
samuel871211 mcollina UlisesGascon
Show details on NVD website
To clipboard 

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    Related by attack behaviour

    Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.