CVE-2026-86414
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HTTP Proxy Credential Leak in libcurl

Publication date: 2026-10-20

Last updated on: 2026-10-30

Assigner: curl

Description
An HTTP proxy can trick libcurl into sending the origin's credentials (Basic password, or a Negotiate/Kerberos ticket) to the proxy itself, by answering the `CONNECT` tunnel request with 401 `WWW-Authenticate:` instead of the expected 407 `Proxy-Authenticate:`.

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Meta Information

Published
2026-10-20
Last Modified
2026-10-30
Generated
2026-11-10
AI Q&A
2026-10-21
EPSS Evaluated
2026-11-08
NVD
CVE-2026-86414

Affected Vendors & Products

Showing 172 associated CPEs
Vendor Product Version / Range
curl curl 8.22.0
curl curl 8.21.0
curl curl 8.20.0
curl curl 8.19.0
curl curl 8.18.0
curl curl 8.17.0
curl curl 8.16.0
curl curl 8.15.0
curl curl 8.14.1
curl curl 8.14.0
curl curl 8.13.0
curl curl 8.12.1
curl curl 8.12.0
curl curl 8.11.1
curl curl 8.11.0
curl curl 8.10.1
curl curl 8.10.0
curl curl 8.9.1
curl curl 8.9.0
curl curl 8.8.0
curl curl 8.7.1
curl curl 8.7.0
curl curl 8.6.0
curl curl 8.5.0
curl curl 8.4.0
curl curl 8.3.0
curl curl 8.2.1
curl curl 8.2.0
curl curl 8.1.2
curl curl 8.1.1
curl curl 8.1.0
curl curl 8.0.1
curl curl 8.0.0
curl curl 7.88.1
curl curl 7.88.0
curl curl 7.87.0
curl curl 7.86.0
curl curl 7.85.0
curl curl 7.84.0
curl curl 7.83.1
curl curl 7.83.0
curl curl 7.82.0
curl curl 7.81.0
curl curl 7.80.0
curl curl 7.79.1
curl curl 7.79.0
curl curl 7.78.0
curl curl 7.77.0
curl curl 7.76.1
curl curl 7.76.0
curl curl 7.75.0
curl curl 7.74.0
curl curl 7.73.0
curl curl 7.72.0
curl curl 7.71.1
curl curl 7.71.0
curl curl 7.70.0
curl curl 7.69.1
curl curl 7.69.0
curl curl 7.68.0
curl curl 7.67.0
curl curl 7.66.0
curl curl 7.65.3
curl curl 7.65.2
curl curl 7.65.1
curl curl 7.65.0
curl curl 7.64.1
curl curl 7.64.0
curl curl 7.63.0
curl curl 7.62.0
curl curl 7.61.1
curl curl 7.61.0
curl curl 7.60.0
curl curl 7.59.0
curl curl 7.58.0
curl curl 7.57.0
curl curl 7.56.1
curl curl 7.56.0
curl curl 7.55.1
curl curl 7.55.0
curl curl 7.54.1
curl curl 7.54.0
curl curl 7.53.1
curl curl 7.53.0
curl curl 7.52.1
curl curl 7.52.0
curl curl 7.51.0
curl curl 7.50.3
curl curl 7.50.2
curl curl 7.50.1
curl curl 7.50.0
curl curl 7.49.1
curl curl 7.49.0
curl curl 7.48.0
curl curl 7.47.1
curl curl 7.47.0
curl curl 7.46.0
curl curl 7.45.0
curl curl 7.44.0
curl curl 7.43.0
curl curl 7.42.1
curl curl 7.42.0
curl curl 7.41.0
curl curl 7.40.0
curl curl 7.39.0
curl curl 7.38.0
curl curl 7.37.1
curl curl 7.37.0
curl curl 7.36.0
curl curl 7.35.0
curl curl 7.34.0
curl curl 7.33.0
curl curl 7.32.0
curl curl 7.31.0
curl curl 7.30.0
curl curl 7.29.0
curl curl 7.28.1
curl curl 7.28.0
curl curl 7.27.0
curl curl 7.26.0
curl curl 7.25.0
curl curl 7.24.0
curl curl 7.23.1
curl curl 7.23.0
curl curl 7.22.0
curl curl 7.21.7
curl curl 7.21.6
curl curl 7.21.5
curl curl 7.21.4
curl curl 7.21.3
curl curl 7.21.2
curl curl 7.21.1
curl curl 7.21.0
curl curl 7.20.1
curl curl 7.20.0
curl curl 7.19.7
curl curl 7.19.6
curl curl 7.19.5
curl curl 7.19.4
curl curl 7.19.3
curl curl 7.19.2
curl curl 7.19.1
curl curl 7.19.0
curl curl 7.18.2
curl curl 7.18.1
curl curl 7.18.0
curl curl 7.17.1
curl curl 7.17.0
curl curl 7.16.4
curl curl 7.16.3
curl curl 7.16.2
curl curl 7.16.1
curl curl 7.16.0
curl curl 7.15.5
curl curl 7.15.4
curl curl 7.15.3
curl curl 7.15.2
curl curl 7.15.1
curl curl 7.15.0
curl curl 7.14.1
curl curl 7.14.0
curl curl 7.13.2
curl curl 7.13.1
curl curl 7.13.0
curl curl 7.12.3
curl curl 7.12.2
curl curl 7.12.1
curl curl 7.12.0
curl curl 7.11.2
curl curl 7.11.1
curl curl 7.11.0
curl curl 7.10.8

Helpful Resources

Exploitability

CWE
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KEV
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CWE ID Description
CWE-201 The code transmits data to another actor, but a portion of the data includes sensitive information that should not be accessible to that actor.

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Executive Summary

This vulnerability involves an HTTP proxy tricking libcurl into sending the origin's credentials (like Basic password or Kerberos ticket) to the proxy itself. Instead of responding to a CONNECT tunnel request with a 407 Proxy-Authenticate header, the proxy incorrectly sends a 401 WWW-Authenticate header.

Detection Guidance

This vulnerability involves an HTTP proxy sending credentials to itself instead of the target server. To detect it, monitor network traffic for CONNECT requests where the proxy responds with 401 WWW-Authenticate instead of 407 Proxy-Authenticate. Use tools like tcpdump or Wireshark to capture and inspect HTTP proxy traffic for mismatched authentication headers.

Impact Analysis

An attacker could exploit this to steal credentials sent to a proxy, potentially gaining unauthorized access to sensitive data or systems. This could lead to data breaches, account compromise, or further network infiltration.

Mitigation Strategies

Update libcurl to the latest patched version. Configure proxies to respond with 407 Proxy-Authenticate instead of 401 WWW-Authenticate for CONNECT requests.

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