CVE-2026-9547

When a libcurl-based application performs transfers via `SCP://` or `SFTP://` and utilizes the `CURLOPT_SSH_KEYFUNCTION` callback, it may silently accept an untrusted server. This vulnerability occurs when a server presents a host key type that does not match the specific key type already recorded for that host in the `known_hosts` file. Instead of rejecting the mismatch, the callback mechanism fails to properly enforce the restriction, allowing the connection to succeed without warning and risking a potential man-in-the-middle attack.

CVSS v3 7.4 HIGH

7.4^/10

CVSS v3 : HIGH

Vector :

Exploitability : 2.2 / Impact : 5.2

Attack Vector NETWORK

Attack Complexity HIGH

Privileges Required NONE

User Interaction NONE

Confidentiality Impact HIGH

Integrity Impact HIGH

Availability Impact NONE

Scope UNCHANGED

References

Link	Resource
https://curl.se/docs/CVE-2026-9547.html	Patch Vendor Advisory
https://curl.se/docs/CVE-2026-9547.json	Vendor Advisory
https://hackerone.com/reports/3751712	Exploit Issue Tracking Third Party Advisory
https://hackerone.com/reports/3751712	Exploit Issue Tracking Third Party Advisory

Configurations

Configuration 1 (hide)

cpe:2.3:a:haxx:curl:*:*:*:*:*:*:*:*

History

No history.

Information

Published : 2026-07-03 07:16

Updated : 2026-09-15 07:16

NVD link : CVE-2026-9547

Mitre link : CVE-2026-9547

CVE.ORG link : CVE-2026-9547

JSON object : View

Products Affected

haxx

curl

CWE

CWE-297

Improper Validation of Certificate with Host Mismatch

NVD-CWE-Other

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This vulnerability occurs when a server presents a host key\ntype that does not match the specific key type already recorded for that host\nin the `known_hosts` file. Instead of rejecting the mismatch, the callback\nmechanism fails to properly enforce the restriction, allowing the connection\nto succeed without warning and risking a potential man-in-the-middle attack."}], "lastModified": "2026-09-15T07:16:35.310", "configurations": [{"nodes": [{"negate": false, "cpeMatch": [{"criteria": "cpe:2.3:a:haxx:curl:*:*:*:*:*:*:*:*", "vulnerable": true, "matchCriteriaId": "384FD0B4-826D-4A6C-9F78-BC25B9039011", "versionEndExcluding": "8.21.0", "versionStartIncluding": "7.69.0"}], "operator": "OR"}]}], "sourceIdentifier": "2499f714-1537-4658-8207-48ae4bb9eae9"}