CVE-2026-9547: SSH improper host validation

Is it exploited?

Not on CISA's list. CISA has not added it to the Known Exploited Vulnerabilities catalog as of 29 Oct 2026. If CISA adds it, this page shows it as known exploited.

How likely is exploitation in the next 30 days?

0.4%

Up from 0.3% on 22 Oct 2026.

EPSS score, percentile 29.9 of all scored records. A probability estimated by FIRST, not a report of exploitation.

CISA's SSVC assessment in the CVE record lists exploitation as poc.

How severe?

7.4 High

CVSS v3.1 base score, from CISA's enrichment of the record

What should I do?

CISA has set no required action, because the vulnerability is not in KEV.

The CVE record links no vendor advisory, patch or mitigation.

Which versions are affected?

Affected

• from 7.69.0 to before 8.14.2
• from 8.15.0 to before 8.16.1
• from 8.17.0 to before 8.20.1
• 8.20.0
• 8.19.0
• 8.18.0

and 9 more in the table below

Versions by product

Source: CISA KEV 2026.10.29, as of 29 Oct 2026; FIRST EPSS, as of 29 Oct 2026; CVE List, as of 29 Oct 2026. About the data.

What to do

Advisories and patches

The CVE record links no vendor advisory, patch or mitigation.

This summary is based on the CVE record as of 29 Oct 2026. Check the vendor's advisory before you act: affected versions and fixes can change.

Affected products and versions

As listed in the CVE record.

Versions not listed are: unaffected.

Versions not listed are: unaffected.

Versions not listed are: unaffected.

And 45 more version entries in the CVE record.

Source: CVE List, as of 29 Oct 2026. About the data.

About this vulnerability

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 f…

Summary: CVE record, as of 29 Oct 2026.

• CISA has not added CVE-2026-9547 to its Known Exploited Vulnerabilities (KEV) catalog, as of 29 Oct 2026.
• The CVE record was published on 3 Jul 2026.
• The CVE record carries a CVSS v3.1 base score of 7.4 (High), taken from CISA's enrichment of the record.
• FIRST's EPSS model puts the probability of exploitation in the next 30 days at 0.4% (percentile 29.9), as of 29 Oct 2026. EPSS is a statistical estimate, not a report of exploitation.
• CISA's SSVC assessment in the CVE record: exploitation poc, automatable no, technical impact total.
• The credits in the CVE record name AISLE as finder.

Source: CISA KEV 2026.10.29, as of 29 Oct 2026; CVE List, as of 29 Oct 2026; FIRST EPSS, as of 29 Oct 2026. About the data.

Description

SSH improper host validation

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.

Source: CVE List, as of 29 Oct 2026. About the data.

Timeline