High
Discourse: Reject literal backslash path separators in iframe src traversal guard
Type: advisorySources: OSV
Discourse is an open-source discussion platform. Prior to 2026.1.8, 2026.6.3, 2026.7.2, and 2026.8.0, the iframe src traversal guard did not treat literal backslashes as path separators after decoded dot segments. A crafted source could therefore pass an allowed_iframes subpath check while browser URL normalization moved the iframe outside the intended allowed path. The resulting iframe could load content from a location that the administrator did not allow. This issue is fixed in versions 2026.1.8, 2026.6.3, 2026.7.2, and 2026.8.0.
- Products
- Not specified
- Affected versions
- Not specified
- Fixed versions
- Not specified
- CVEs
- CVE-2026-91123
- Confirmed fixed CVEs
- Not specified
- Updated in this feed
- 4 Nov 2026, 02:13 UTC · Revision 1
Source evidence
Discourse: Reject literal backslash path separators in iframe src traversal guard
core-osv · Original sourcePublished 24 Sept 2026, 16:54 UTC
Discourse is an open-source discussion platform. Prior to 2026.1.8, 2026.6.3, 2026.7.2, and 2026.8.0, the iframe src traversal guard did not treat literal backslashes as path separators after decoded dot segments. A crafted source could therefore pass an allowed_iframes subpath check while browser URL normalization moved the iframe outside the intended allowed path. The resulting iframe could load content from a location that the administrator did not allow. This issue is fixed in versions 2026.1.8, 2026.6.3, 2026.7.2, and 2026.8.0.
osv:CVE-2026-91123
Complete source record
{
"id": "d74c3f16a825d475f2ea56dcc65761fea4e6bf07f81d51390ff61896e6ef7847",
"url": "https://osv.dev/vulnerability/CVE-2026-91123",
"method": "structured",
"payload": {
"kind": "advisory",
"title": "Discourse: Reject literal backslash path separators in iframe src traversal guard",
"summary": "Discourse is an open-source discussion platform. Prior to 2026.1.8, 2026.6.3, 2026.7.2, and 2026.8.0, the iframe src traversal guard did not treat literal backslashes as path separators after decoded dot segments. A crafted source could therefore pass an allowed_iframes subpath check while browser URL normalization moved the iframe outside the intended allowed path. The resulting iframe could load content from a location that the administrator did not allow. This issue is fixed in versions 2026.1.8, 2026.6.3, 2026.7.2, and 2026.8.0.",
"evidence": "osv:CVE-2026-91123",
"products": [],
"severity": "high",
"structured": {
"id": "CVE-2026-91123",
"aliases": [
"BIT-discourse-2026-91123",
"CVE-2026-91123",
"GHSA-6pwj-wgg8-4rjc"
],
"metrics": [
{
"type": "CVSS_V3",
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:N"
}
],
"affected": [
{
"ranges": [
{
"repo": "https://github.com/discourse/discourse",
"type": "GIT",
"events": [
{
"introduced": "0"
},
{
"fixed": "fb9247e04a826ab8e4d91168b3c4c839ec40bccc"
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{
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{
"fixed": "3ab62a8397926ed934b667a5db06284c45b4c774"
},
{
"introduced": "06d03da34c4ed09ea59f917f045ba250d2b6320d"
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{
"fixed": "777cb880553b517bc9ae502e935a160332e48b78"
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{
"introduced": "322d3c0ac6a8f133b3f82875e9dbbe310f638c1b"
},
{
"fixed": "e808d0853e013abf90e648e53ebd606c49ccb19f"
},
{
"fixed": "042d7b159beda4f74d23e245e8b2e396d9ff8318"
},
{
"fixed": "097ce5600a2d74d9c68e57974597ab2684bd2a24"
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{
"fixed": "0b5a27e689925edce9ba9b14110022435d2b94be"
},
{
"fixed": "142f5155ad8e56ddb8012c4e70c69a03dedc0579"
}
],
"database_specific": {
"extracted_events": [
{
"range": [
{
"introduced": "0"
},
{
"fixed": "2026.8.0"
}
],
"source": "AFFECTED_FIELD",
"strategy": "StringRangeExpression"
},
{
"range": [
{
"introduced": "2026.7.0-latest"
},
{
"fixed": "2026.7.2"
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],
"source": "AFFECTED_FIELD",
"strategy": "StringRangeExpression"
},
{
"range": [
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"introduced": "2026.6.0-latest"
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{
"fixed": "2026.6.3"
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"source": "AFFECTED_FIELD",
"strategy": "StringRangeExpression"
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"range": [
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"fixed": "2026.1.8"
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"source": "AFFECTED_FIELD",
"strategy": "StringRangeExpression"
},
{
"range": [
{
"fixed": "042d7b159beda4f74d23e245e8b2e396d9ff8318"
}
],
"source": "REFERENCES_COMMIT"
},
{
"range": [
{
"fixed": "097ce5600a2d74d9c68e57974597ab2684bd2a24"
}
],
"source": "REFERENCES_COMMIT"
},
{
"range": [
{
"fixed": "0b5a27e689925edce9ba9b14110022435d2b94be"
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],
"source": "REFERENCES_COMMIT"
},
{
"range": [
{
"fixed": "142f5155ad8e56ddb8012c4e70c69a03dedc0579"
}
],
"source": "REFERENCES_COMMIT"
}
]
}
}
],
"versions": [
"v2026.1.7",
"v2026.7.1",
"v2026.6.2",
"v2026.1.6",
"v2026.7.0",
"v2026.6.1",
"_gh-attach-assets",
"v2026.1.5",
"v2026.6.0",
"v2026.7.0-latest",
"v2026.6.0-latest",
"v2026.1.4",
"v2026.1.3",
"v2026.1.2",
"v2026.1.1",
"v2026.1.0",
"stable",
"esr",
"v2026.1.0-latest"
],
"database_specific": {
"source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-91123.json"
}
}
],
"modified": "2026-10-28T02:30:32.458966338Z",
"provider": "osv",
"references": [
"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/91xxx/CVE-2026-91123.json",
"https://github.com/discourse/discourse/security/advisories/GHSA-6pwj-wgg8-4rjc",
"https://nvd.nist.gov/vuln/detail/CVE-2026-91123",
"https://github.com/discourse/discourse/commit/042d7b159beda4f74d23e245e8b2e396d9ff8318",
"https://github.com/discourse/discourse/commit/097ce5600a2d74d9c68e57974597ab2684bd2a24",
"https://github.com/discourse/discourse/commit/0b5a27e689925edce9ba9b14110022435d2b94be",
"https://github.com/discourse/discourse/commit/142f5155ad8e56ddb8012c4e70c69a03dedc0579",
"https://github.com/discourse/discourse/pull/42882"
],
"provider_metadata": {
"cwe_ids": [
"CWE-22"
],
"cna_assigner": "GitHub_M",
"osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/91xxx/CVE-2026-91123.json"
}
},
"related_cves": [
{
"value": "CVE-2026-91123",
"evidence": "/id"
}
],
"security_relevant": true,
"severity_evidence": "/severity/0/score"
},
"source_id": "core-osv",
"document_id": 499575,
"published_at": "2026-09-24T16:54:59.357+00:00"
}