Low
SSH improper host validation
Type: advisorySources: OSV
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.
- Products
- Not specified
- Affected versions
- Not specified
- Fixed versions
- Not specified
- CVEs
- CVE-2026-9547
- Confirmed fixed CVEs
- Not specified
- Updated in this feed
- 1 Nov 2026, 09:39 UTC · Revision 1
Source evidence
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.
osv:CURL-CVE-2026-9547
Complete source record
{
"id": "87a4d68108c0588bae962272a70282e3d8a04e509a79e0a4c07de30fb13bf032",
"url": "https://osv.dev/vulnerability/CURL-CVE-2026-9547",
"method": "structured",
"payload": {
"kind": "advisory",
"title": "SSH improper host validation",
"summary": "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.",
"evidence": "osv:CURL-CVE-2026-9547",
"products": [],
"severity": "low",
"structured": {
"id": "CURL-CVE-2026-9547",
"aliases": [
"CURL-CVE-2026-9547",
"CVE-2026-9547"
],
"affected": [
{
"ranges": [
{
"type": "SEMVER",
"events": [
{
"introduced": "7.69.0"
},
{
"fixed": "8.14.2"
},
{
"introduced": "8.15.0"
},
{
"fixed": "8.16.1"
},
{
"introduced": "8.17.0"
},
{
"fixed": "8.20.1"
},
{
"introduced": "8.21.0"
},
{
"fixed": "8.21.0"
}
]
},
{
"repo": "https://github.com/curl/curl.git",
"type": "GIT",
"events": [
{
"introduced": "507cf6a13db0375eadd4655b4c64710db29e9cf2"
},
{
"fixed": "0b8dbbc63c98777e4584cb9fbd71df3464008ad1"
}
]
}
],
"versions": [
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"8.19.0",
"8.18.0",
"8.17.0",
"8.16.0",
"8.15.0",
"8.14.1",
"8.14.0",
"8.13.0",
"8.12.1",
"8.12.0",
"8.11.1",
"8.11.0",
"8.10.1",
"8.10.0",
"8.9.1",
"8.9.0",
"8.8.0",
"8.7.1",
"8.7.0",
"8.6.0",
"8.5.0",
"8.4.0",
"8.3.0",
"8.2.1",
"8.2.0",
"8.1.2",
"8.1.1",
"8.1.0",
"8.0.1",
"8.0.0",
"7.88.1",
"7.88.0",
"7.87.0",
"7.86.0",
"7.85.0",
"7.84.0",
"7.83.1",
"7.83.0",
"7.82.0",
"7.81.0",
"7.80.0",
"7.79.1",
"7.79.0",
"7.78.0",
"7.77.0",
"7.76.1",
"7.76.0",
"7.75.0",
"7.74.0",
"7.73.0",
"7.72.0",
"7.71.1",
"7.71.0",
"7.70.0",
"7.69.1",
"7.69.0",
"curl-8_20_0",
"rc-8_20_0-3",
"rc-8_20_0-2",
"rc-8_20_0-1",
"curl-8_19_0",
"rc-8_19_0-3",
"rc-8_19_0-2",
"rc-8_19_0-1",
"curl-8_18_0",
"rc-8_18_0-3",
"rc-8_18_0-2",
"rc-8_18_0-1",
"curl-8_17_0",
"curl-8_16_0",
"curl-8_15_0",
"curl-8_14_1",
"curl-8_14_0",
"curl-8_13_0",
"curl-8_12_1",
"curl-8_12_0",
"curl-8_11_1",
"curl-8_11_0",
"curl-8_10_1",
"curl-8_10_0",
"curl-8_9_1",
"curl-8_9_0",
"curl-8_8_0",
"curl-8_7_1",
"curl-8_7_0",
"curl-8_6_0",
"curl-8_5_0",
"tiny-curl-8_4_0",
"curl-8_4_0",
"curl-8_3_0",
"curl-8_2_1",
"curl-8_2_0",
"curl-8_1_2",
"curl-8_1_1",
"curl-8_1_0",
"curl-8_0_1",
"curl-8_0_0",
"curl-7_88_1",
"curl-7_88_0",
"curl-7_87_0",
"curl-7_86_0",
"curl-7_85_0",
"curl-7_84_0",
"curl-7_83_1",
"curl-7_83_0",
"curl-7_82_0",
"curl-7_81_0",
"curl-7_80_0",
"curl-7_79_1",
"curl-7_79_0",
"curl-7_78_0",
"curl-7_77_0",
"curl-7_76_1",
"curl-7_76_0",
"curl-7_75_0",
"curl-7_74_0",
"curl-7_73_0",
"tiny-curl-7_72_0",
"curl-7_72_0",
"curl-7_71_1",
"curl-7_71_0",
"curl-7_70_0",
"curl-7_69_1",
"curl-7_69_0"
],
"database_specific": {
"source": "https://curl.se/docs/CURL-CVE-2026-9547.json",
"vanir_signatures": [
{
"id": "CURL-CVE-2026-9547-e5ddacc0",
"digest": {
"length": 4615,
"function_hash": "171591672620915120098914005398439744356"
},
"source": "https://github.com/curl/curl.git/commit/0b8dbbc63c98777e4584cb9fbd71df3464008ad1",
"target": {
"file": "lib/vssh/libssh.c",
"function": "myssh_is_known"
},
"deprecated": false,
"signature_type": "Function",
"signature_version": "v1"
},
{
"id": "CURL-CVE-2026-9547-ffd5c5b3",
"digest": {
"threshold": 0.9,
"line_hashes": [
"19522727956082994505377891717732253881",
"17505745399782688697084999810884215111",
"65466782891270922555303879365870593631",
"39998244195617753293703183793609467932"
]
},
"source": "https://github.com/curl/curl.git/commit/0b8dbbc63c98777e4584cb9fbd71df3464008ad1",
"target": {
"file": "lib/vssh/libssh.c"
},
"deprecated": false,
"signature_type": "Line",
"signature_version": "v1"
}
],
"vanir_signatures_modified": "2026-10-25T01:05:45Z"
}
}
],
"modified": "2026-10-25T01:05:45.818362850Z",
"provider": "osv",
"references": [],
"provider_metadata": {
"CWE": {
"id": "CWE-297",
"desc": "Improper Validation of Certificate with Host Mismatch"
},
"URL": "https://curl.se/docs/CVE-2026-9547.json",
"www": "https://curl.se/docs/CVE-2026-9547.html",
"issue": "https://hackerone.com/reports/3751712",
"affects": "lib",
"package": "curl",
"severity": "Low",
"last_affected": "8.20.0"
}
},
"related_cves": [
{
"value": "CVE-2026-9547",
"evidence": "/aliases"
}
],
"security_relevant": true,
"severity_evidence": "/database_specific/severity"
},
"source_id": "core-osv",
"document_id": 444427,
"published_at": "2026-06-24T08:00:00+00:00"
}