Critical
Security advisory
Http4s is a minimal, idiomatic Scala interface for HTTP services. In http4s versions 0.21.26 and prior, 0.22.0 through 0.22.2, 0.23.0, 0.23.1, and 1.0.0-M1 through 1.0.0-M24, the default CORS configuration is vulnerable to an origin reflection attack. The middleware is also susceptible to a Null Origin Attack. The problem is fixed in 0.21.27, 0.22.3, 0.23.2, and 1.0.0-M25. The original `CORS` implementation and `CORSConfig` are deprecated. See the GitHub GHSA for more information, including code examples and workarounds.
- Products
- Not specified
- Affected versions
- Not specified
- Fixed versions
- Not specified
- CVEs
- CVE-2021-39185
- Confirmed fixed CVEs
- Not specified
- Updated in this feed
- 31 Oct 2026, 11:52 UTC · Revision 1
Source evidence
Http4s is a minimal, idiomatic Scala interface for HTTP services. In http4s versions 0.21.26 and prior, 0.22.0 through 0.22.2, 0.23.0, 0.23.1, and 1.0.0-M1 through 1.0.0-M24, the default CORS configuration is vulnerable to an origin reflection attack. The middleware is also susceptible to a Null Origin Attack. The problem is fixed in 0.21.27, 0.22.3, 0.23.2, and 1.0.0-M25. The original `CORS` implementation and `CORSConfig` are deprecated. See the GitHub GHSA for more information, including code examples and workarounds.
osv:CVE-2021-39185
Complete source record
{
"id": "f33cc757432cfc8254e71abf2095afe649cf7c1376b4c46265d4089d09508dfa",
"url": "https://osv.dev/vulnerability/CVE-2021-39185",
"method": "structured",
"payload": {
"kind": "advisory",
"title": "CVE-2021-39185",
"summary": "Http4s is a minimal, idiomatic Scala interface for HTTP services. In http4s versions 0.21.26 and prior, 0.22.0 through 0.22.2, 0.23.0, 0.23.1, and 1.0.0-M1 through 1.0.0-M24, the default CORS configuration is vulnerable to an origin reflection attack. The middleware is also susceptible to a Null Origin Attack. The problem is fixed in 0.21.27, 0.22.3, 0.23.2, and 1.0.0-M25. The original `CORS` implementation and `CORSConfig` are deprecated. See the GitHub GHSA for more information, including code examples and workarounds.",
"evidence": "osv:CVE-2021-39185",
"products": [],
"severity": "critical",
"structured": {
"id": "CVE-2021-39185",
"aliases": [
"CVE-2021-39185",
"GHSA-52cf-226f-rhr6"
],
"metrics": [
{
"type": "CVSS_V3",
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N"
}
],
"affected": [
{
"ranges": [
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"type": "GIT",
"events": [
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},
{
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},
{
"introduced": "3e98ea4a63e741c7f9d5e917d48d2ee8fab54476"
},
{
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},
{
"introduced": "06db471f053023ce3ffd7c568ce46d33551d1d69"
},
{
"last_affected": "6676c1e24a4e32e0c6c1a36911f4e6606c10e12b"
},
{
"fixed": "5ebfb746ff98817959cbcce3ab2520342253c608"
}
],
"database_specific": {
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{
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{
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{
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{
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{
"cpe": "cpe:2.3:a:typelevel:http4s:1.0.0:milestone11:*:*:*:*:*:*",
"range": [
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}
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{
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"range": [
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"source": "CPE_STRING"
},
{
"cpe": "cpe:2.3:a:typelevel:http4s:1.0.0:milestone13:*:*:*:*:*:*",
"range": [
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"range": [
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"source": "CPE_STRING"
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{
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"range": [
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{
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"source": "CPE_STRING"
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{
"cpe": "cpe:2.3:a:typelevel:http4s:1.0.0:milestone17:*:*:*:*:*:*",
"range": [
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"source": "CPE_STRING"
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{
"cpe": "cpe:2.3:a:typelevel:http4s:1.0.0:milestone18:*:*:*:*:*:*",
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{
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{
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{
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{
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"source": "CPE_STRING"
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{
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{
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"range": [
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{
"cpe": "cpe:2.3:a:typelevel:http4s:1.0.0:milestone9:*:*:*:*:*:*",
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{
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"source": "REFERENCES_TAG",
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}
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"v0.20.0",
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],
"database_specific": {
"source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2021-39185.json"
}
}
],
"modified": "2026-10-20T10:54:53.199576583Z",
"provider": "osv",
"references": [
"https://github.com/http4s/http4s/releases/tag/v0.23.2",
"https://github.com/http4s/http4s/security/advisories/GHSA-52cf-226f-rhr6"
],
"provider_metadata": {}
},
"related_cves": [
{
"value": "CVE-2021-39185",
"evidence": "/id"
}
],
"security_relevant": true,
"severity_evidence": "/severity/0/score"
},
"source_id": "core-osv",
"document_id": 386364,
"published_at": "2021-09-01T20:15:07.447+00:00"
}