High
Starlette: SSRF and NTLM credential theft via UNC paths in StaticFiles on Windows
Type: advisorySources: OSV
Starlette is a lightweight ASGI framework/toolkit. In versions 1.0.1 and earlier, StaticFiles on Windows is vulnerable to SSRF. An UNC path such as \\attacker.com\share can cause os.path.realpath to initiate an outbound SMB connection before the path is rejected, exposing the service account’s NTLMv2 credentials for offline cracking or relay even though the HTTP response is only a 404. The issue affects default follow_symlink=False deployments, including frameworks built on Starlette such as FastAPI; POSIX systems and follow_symlink=True are unaffected. The issue is fixed in 1.1.0.
- Products
- Not specified
- Affected versions
- Not specified
- Fixed versions
- Not specified
- CVEs
- CVE-2026-48818
- Confirmed fixed CVEs
- Not specified
- Updated in this feed
- 2 Nov 2026, 21:19 UTC · Revision 1
Source evidence
Starlette: SSRF and NTLM credential theft via UNC paths in StaticFiles on Windows
core-osv · Original sourcePublished 17 Jun 2026, 17:50 UTC
Starlette is a lightweight ASGI framework/toolkit. In versions 1.0.1 and earlier, StaticFiles on Windows is vulnerable to SSRF. An UNC path such as \\attacker.com\share can cause os.path.realpath to initiate an outbound SMB connection before the path is rejected, exposing the service account’s NTLMv2 credentials for offline cracking or relay even though the HTTP response is only a 404. The issue affects default follow_symlink=False deployments, including frameworks built on Starlette such as FastAPI; POSIX systems and follow_symlink=True are unaffected. The issue is fixed in 1.1.0.
osv:CVE-2026-48818
Complete source record
{
"id": "bbe5f9cf981ce7b04ce26642ab22f271f380200caaece3c12fa05a22b575ef13",
"url": "https://osv.dev/vulnerability/CVE-2026-48818",
"method": "structured",
"payload": {
"kind": "advisory",
"title": "Starlette: SSRF and NTLM credential theft via UNC paths in StaticFiles on Windows",
"summary": "Starlette is a lightweight ASGI framework/toolkit. In versions 1.0.1 and earlier, StaticFiles on Windows is vulnerable to SSRF. An UNC path such as \\\\attacker.com\\share can cause os.path.realpath to initiate an outbound SMB connection before the path is rejected, exposing the service account’s NTLMv2 credentials for offline cracking or relay even though the HTTP response is only a 404. The issue affects default follow_symlink=False deployments, including frameworks built on Starlette such as FastAPI; POSIX systems and follow_symlink=True are unaffected. The issue is fixed in 1.1.0.",
"evidence": "osv:CVE-2026-48818",
"products": [],
"severity": "high",
"structured": {
"id": "CVE-2026-48818",
"aliases": [
"CVE-2026-48818",
"GHSA-wqp7-x3pw-xc5r",
"PYSEC-2026-2281"
],
"metrics": [
{
"type": "CVSS_V3",
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N"
}
],
"affected": [
{
"ranges": [
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"type": "GIT",
"events": [
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{
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{
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{
"fixed": "1.1.0"
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"source": "CPE_RANGE"
},
{
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],
"source": "REFERENCES_COMMIT"
},
{
"range": [
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"source": "REFERENCES_TAG",
"original_tag": "1.1.0"
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"database_specific": {
"source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-48818.json"
}
}
],
"modified": "2026-10-28T02:30:23.600008911Z",
"provider": "osv",
"references": [
"https://github.com/Kludex/starlette/releases/tag/1.1.0",
"https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-48818.json",
"https://access.redhat.com/errata/RHSA-2026:30087",
"https://access.redhat.com/errata/RHSA-2026:30088",
"https://access.redhat.com/errata/RHSA-2026:30089",
"https://access.redhat.com/security/cve/CVE-2026-48818",
"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/48xxx/CVE-2026-48818.json",
"https://github.com/Kludex/starlette/security/advisories/GHSA-wqp7-x3pw-xc5r",
"https://github.com/pypa/advisory-database/tree/main/vulns/starlette/PYSEC-2026-2281.yaml",
"https://nvd.nist.gov/vuln/detail/CVE-2026-48818",
"https://bugzilla.redhat.com/show_bug.cgi?id=2490020",
"https://github.com/Kludex/starlette/commit/fd53168a7767b6b55ba5af787fd88f49e33cabc5",
"https://github.com/Kludex/starlette/pull/3287"
],
"provider_metadata": {
"cwe_ids": [
"CWE-918"
],
"cna_assigner": "GitHub_M",
"osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/48xxx/CVE-2026-48818.json"
}
},
"related_cves": [
{
"value": "CVE-2026-48818",
"evidence": "/id"
}
],
"security_relevant": true,
"severity_evidence": "/severity/0/score"
},
"source_id": "core-osv",
"document_id": 490210,
"published_at": "2026-06-17T17:50:12.399+00:00"
}