by Kastro
Paper/Archive/CVE-2026-86414

CVE-2026-86414

curl curl — leaking host credentials to HTTP proxy

EPSS 0.3%public exploitCVSS 9.1
critical.is priorityof 100
41
CVSS 9.1 (ADP)9.1 / 10 × 3027.3Not in CISA KEV+300.0EPSS percentile 18.6.186 × 203.7Exploit: SSVC poc+1010.0SSVC exploitation: poc+100.0
Description · from the CVE record

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:`.

Affected

ProductAffectedFixed inSource
curl8.22.0 – 8.22.0–CNA
curl8.21.0 – 8.21.0–CNA
curl8.20.0 – 8.20.0–CNA
curl8.19.0 – 8.19.0–CNA
curl8.18.0 – 8.18.0–CNA
curl8.17.0 – 8.17.0–CNA
curl8.16.0 – 8.16.0–CNA
curl8.15.0 – 8.15.0–CNA
curl8.14.1 – 8.14.1–CNA
curl8.14.0 – 8.14.0–CNA
curl8.13.0 – 8.13.0–CNA
curl8.12.1 – 8.12.1–CNA

Scores by source

CISA ADP9.1CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
CISA ADPSSVCExploitation: poc · Automatable: yes · Technical impact: total

References

refcurl.se/docs/CVE-2026-86414.jsonrefcurl.se/docs/CVE-2026-86414.htmlexploithackerone.com/reports/3993566