CVE-2026-9547 - Vulnerability Details - OpenCVE

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.

No CVSS v4.0

No CVSS v3.1

No CVSS v3.0

No CVSS v2

This CVE is not in the KEV list.

No EPSS score available.

Key SSVC decision points have not yet been added.

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References

Link	Providers
https://curl.se/docs/CVE-2026-9547.html
https://curl.se/docs/CVE-2026-9547.json
https://hackerone.com/reports/3751712

History

Fri, 03 Jul 2026 06:45:00 +0000

Type	Values Removed	Values Added
Description		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.
Title		SSH improper host validation
References		https://curl.se/docs/CVE-2026-9547.html https://curl.se/docs/CVE-2026-9547.json https://hackerone.com/reports/3751712

MITRE

Status: PUBLISHED

Assigner: curl

Published: 2026-07-03T06:18:44.499Z

Updated: 2026-07-03T06:18:44.499Z

Reserved: 2026-05-26T06:45:27.665Z

Link: CVE-2026-9547

Vulnrichment

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NVD

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Redhat

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OpenCVE Enrichment

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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."}], "providerMetadata": {"orgId": "2499f714-1537-4658-8207-48ae4bb9eae9", "shortName": "curl", "dateUpdated": "2026-07-03T06:18:44.499Z"}, "problemTypes": [{"descriptions": [{"lang": "en", "description": "CWE-297 Improper Validation of Certificate with Host Mismatch"}]}], "affected": [{"vendor": "curl", "product": "curl", "versions": [{"version": "8.20.0", "status": "affected", "lessThanOrEqual": "8.20.0", "versionType": "semver"}, {"version": "8.19.0", "status": "affected", "lessThanOrEqual": "8.19.0", "versionType": "semver"}, {"version": "8.18.0", "status": "affected", "lessThanOrEqual": "8.18.0", "versionType": "semver"}, {"version": "8.17.0", "status": "affected", "lessThanOrEqual": "8.17.0", "versionType": "semver"}, {"version": "8.16.0", "status": "affected", "lessThanOrEqual": 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