CVE-2026-9547 | SSH improper host validation

Exp

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.

Published: 2026-07-03 Last update: 2026-07-07 Assigner: 2499f714-1537-4658-8207-48ae4bb9eae9 Source: 2499f714-1537-4658-8207-48ae4bb9eae9
NVD Status：Analyzed，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2026-9547 is rated Exploit Available (55.4/100): CVSS High severity, with low exploitation likelihood (EPSS 0.38%). 1 public exploit reference(s) are indexed (Exploit-DB). Public exploits are available—assess exposure, apply mitigations, and prioritize patching.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Public exploit references (Exploit-DB) for CVE-2026-9547

EDB-ID Source Kind Published Link
— nvd_ref exploit_tag Exploit-DB ↗

Exploit prediction scoring system (EPSS) score for CVE-2026-9547

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-07-07 0.19% 0.38% +0.20%
2 2026-07-04 — 0.19% —

Full EPSS history (2 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2026-9547

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
7.4 3.1 HIGH
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:H)
Even with access, the exploit needs extra luck, timing, or a fussy environment to actually work.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:H)
Serious risk that confidential data gets exposed in a big way.
Integrity (I:H)
They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:N)
Service keeps running; no real outage angle.
 2.2 5.2 134c704f-9b21-4f2e-91b3-4a467353bcc0

Weakness enumeration for CVE-2026-9547

GitHub Security Advisory for CVE-2026-9547

GHSA-xq9p-gxg6-f7q6 · Severity: high — When a libcurl-based application performs transfers via `SCP://` or `SFTP://` and utilizes the ...

OS Trackers for CVE-2026-9547

vendor priority summary link
debian not yet assigned CVE-2026-9547 not yet assigned priority: Debian including 1 source packages (curl), 5 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): open 4, resolved 1. https://security-tracker.debian.org/tracker/CVE-2026-9547
ubuntu low CVE-2026-9547 low priority: Ubuntu including 1 source packages (curl), 9 status rows across 9 suites (bionic, focal, jammy, noble, questing, resolute, trusty, upstream, xenial): not-affected 4, released 4, pending 1. https://ubuntu.com/security/CVE-2026-9547

Affected software / configurations for CVE-2026-9547

Vendor Product Version Raw CPE
haxx curl >= 7.69.0, < 8.21.0 cpe:2.3:a:haxx:curl:*:*:*:*:*:*:*:*

References for CVE-2026-9547

URL Tags
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
cvelogic Threat Intelligence