CVE-2026-9547

HIGHCVSS 7.4/10EPSS 0.38%

Last modified

CVE-2026-9547 is a high-severity vulnerability rated 7.4/10 on the CVSS scale. 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. EPSS estimates a 0.38% chance of exploitation in the next 30 days.

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.

Metrics

CVSS 3.1
7.4/10

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N

EPSS Probability
0.38%

30.4th percentile

Probability of exploitation in the next 30 days. Learn more

Affected Software

VendorProductVersions
HaxxCurl>= 7.69.0, < 8.21.0

References

Timeline

Published
Last Modified
Status
Analyzed

Frequently Asked Questions

What is 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.
How severe is CVE-2026-9547?
CVE-2026-9547 has a CVSS score of 7.4/10 (HIGH severity). The EPSS model estimates a 0.38% probability of exploitation in the next 30 days.
How do I fix CVE-2026-9547?
Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

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Source: NVD / NIST