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Vulnerability record · CVE-2026-9547 · published 3 July 2026

CVE-2026-9547: Haxx curl vulnerability

Haxx · Curl

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.

7.4 CVSS 3.1 High EPSS 0.51% · top 59.1% CWE-297 · CWE-297
7.4CVSS 3.1 base score
0.51%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
4References, 2 tagged exploit
15 Sep 2026Last modified by NVD

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.

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

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://curl.se/docs/CVE-2026-9547.html PatchVendor Advisory
https://curl.se/docs/CVE-2026-9547.json Vendor Advisory
https://hackerone.com/reports/3751712 ExploitIssue TrackingThird Party Advisory
https://hackerone.com/reports/3751712 ExploitIssue TrackingThird Party Advisory

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Related vulnerabilities

Same products first, then exploited flaws of the same weakness class.

9.8CVE-2026-19931Haxx curl vulnerabilityA flaw in libcurl makes it wrongly reuse an HTTP connection setup for a given hostname using Negotiate authentication, when the initial request is do…EPSS 0.75%9.8CVE-2026-9079Haxx curl insufficiently protected credentials vulnerabilitylibcurl had a flaw that when instructed to clear proxy authentication credentials which made it not do so, leaving the old credentials around to get …EPSS 0.58%9.8CVE-2026-8925Haxx curl double free vulnerabilityThe curl logic that works with SASL authentication could end up cleaning up the GSASL context *twice* without clearing the pointer in between, making…EPSS 1.1%9.8CVE-2026-10536Haxx curl use after free vulnerabilityA use-after-free vulnerability exists in libcurl when an application configures an HTTP/2 stream-dependency tree via `CURLOPT_STREAM_DEPENDS` or `CUR…EPSS 0.60%9.8CVE-2026-11856Haxx curl authentication bypass by capture-replay vulnerabilitySuccessfully using libcurl to do a transfer to a specific HTTP origin (`hostA`) with **Digest** authentication and then changing the origin to a diff…EPSS 0.69%9.8CVE-2022-32221Haxx curl information exposure vulnerabilityWhen doing HTTP(S) transfers, libcurl might erroneously use the read callback (`CURLOPT_READFUNCTION`) to ask for data to send, even when the `CURLOP…EPSS 4.4%9.8CVE-2022-32207Haxx curl incorrect default permissions vulnerabilityWhen curl < 7.84.0 saves cookies, alt-svc and hsts data to local files, it makes the operation atomic by finalizing the operation with a rename from …EPSS 7.7%9.8CVE-2016-4606Haxx curl vulnerabilityCurl before 7.49.1 in Apple OS X before macOS Sierra prior to 10.12 allows remote or local attackers to execute arbitrary code, gain sensitive inform…EPSS 3.4%

Source: NIST National Vulnerability Database (record CVE-2026-9547), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.