CVE-2026-63439 (GCVE-0-2026-63439)
Vulnerability from cvelistv5 – Published: 2026-11-06 20:22 – Updated: 2026-11-09 13:20
VLAI
EPSS
VEX
Title
2FAuth: Reverse Proxy Guard Trusts Client-Supplied Headers Without Proxy Verification
Summary
2FAuth is a web app to manage Two-Factor Authentication (2FA) accounts and generate their security codes. Prior to 8.0.0, when AUTHENTICATION_GUARD=reverse-proxy-guard is enabled, ReverseProxyGuard::user() reads the default REMOTE_USER identity header, or a custom identity header selected by the AUTH_PROXY_HEADER_FOR_USER configuration setting, without confirming that the request originated from a configured trusted proxy. A remote client that can reach the application directly can forge the selected identity header and authenticate as an existing user, including an administrator, gaining access to stored 2FA secrets and account or application management functions. This issue is fixed in version 8.0.0.
Severity
9.8 (Critical)
SSVC
Exploitation: poc
Automatable: yes
Technical Impact: total
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-11-09 13:20 UTC
CWE
- CWE-287 - Improper Authentication
Assigner
GitHub_M
CNA
References
3 references
| URL | Tags |
|---|---|
| https://github.com/Bubka/2FAuth/security/advisori… | x_refsource_CONFIRM |
| https://github.com/Bubka/2FAuth/commit/43873cbfba… | x_refsource_MISC |
| https://github.com/Bubka/2FAuth/releases/tag/v8.0.0 | x_refsource_MISC |
{
"containers": {
"adp": [
{
"metrics": [
{
"other": {
"content": {
"id": "CVE-2026-63439",
"options": [
{
"Exploitation": "poc"
},
{
"Automatable": "yes"
},
{
"Technical Impact": "total"
}
],
"role": "CISA Coordinator",
"timestamp": "2026-11-09T13:20:03.819595Z",
"version": "2.0.3"
},
"type": "ssvc"
}
}
],
"providerMetadata": {
"dateUpdated": "2026-11-09T13:20:36.761Z",
"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
"shortName": "CISA-ADP"
},
"references": [
{
"tags": [
"exploit"
],
"url": "https://github.com/Bubka/2FAuth/security/advisories/GHSA-mh8r-74x2-r457"
}
],
"title": "CISA ADP Vulnrichment"
}
],
"cna": {
"affected": [
{
"product": "2FAuth",
"vendor": "Bubka",
"versions": [
{
"status": "affected",
"version": "\u003c 8.0.0"
}
]
}
],
"descriptions": [
{
"lang": "en",
"value": "2FAuth is a web app to manage Two-Factor Authentication (2FA) accounts and generate their security codes. Prior to 8.0.0, when AUTHENTICATION_GUARD=reverse-proxy-guard is enabled, ReverseProxyGuard::user() reads the default REMOTE_USER identity header, or a custom identity header selected by the AUTH_PROXY_HEADER_FOR_USER configuration setting, without confirming that the request originated from a configured trusted proxy. A remote client that can reach the application directly can forge the selected identity header and authenticate as an existing user, including an administrator, gaining access to stored 2FA secrets and account or application management functions. This issue is fixed in version 8.0.0."
}
],
"metrics": [
{
"cvssV3_1": {
"attackComplexity": "LOW",
"attackVector": "NETWORK",
"availabilityImpact": "HIGH",
"baseScore": 9.8,
"baseSeverity": "CRITICAL",
"confidentialityImpact": "HIGH",
"integrityImpact": "HIGH",
"privilegesRequired": "NONE",
"scope": "UNCHANGED",
"userInteraction": "NONE",
"vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
"version": "3.1"
}
}
],
"problemTypes": [
{
"descriptions": [
{
"cweId": "CWE-287",
"description": "CWE-287: Improper Authentication",
"lang": "en",
"type": "CWE"
}
]
}
],
"providerMetadata": {
"dateUpdated": "2026-11-06T20:22:31.651Z",
"orgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
"shortName": "GitHub_M"
},
"references": [
{
"name": "https://github.com/Bubka/2FAuth/security/advisories/GHSA-mh8r-74x2-r457",
"tags": [
"x_refsource_CONFIRM"
],
"url": "https://github.com/Bubka/2FAuth/security/advisories/GHSA-mh8r-74x2-r457"
},
{
"name": "https://github.com/Bubka/2FAuth/commit/43873cbfba445926c7008b4291eeee67752af9e8",
"tags": [
"x_refsource_MISC"
],
"url": "https://github.com/Bubka/2FAuth/commit/43873cbfba445926c7008b4291eeee67752af9e8"
},
{
"name": "https://github.com/Bubka/2FAuth/releases/tag/v8.0.0",
"tags": [
"x_refsource_MISC"
],
"url": "https://github.com/Bubka/2FAuth/releases/tag/v8.0.0"
}
],
"source": {
"advisory": "GHSA-mh8r-74x2-r457",
"discovery": "UNKNOWN"
},
"title": "2FAuth: Reverse Proxy Guard Trusts Client-Supplied Headers Without Proxy Verification"
}
},
"cveMetadata": {
"assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
"assignerShortName": "GitHub_M",
"cveId": "CVE-2026-63439",
"datePublished": "2026-11-06T20:22:31.651Z",
"dateReserved": "2026-07-16T19:35:57.767Z",
"dateUpdated": "2026-11-09T13:20:36.761Z",
"state": "PUBLISHED"
},
"dataType": "CVE_RECORD",
"dataVersion": "5.2",
"vulnerability-lookup:meta": {
"vulnrichment": {
"containers": {
"adp": [
{
"metrics": [
{
"other": {
"content": {
"id": "CVE-2026-63439",
"options": [
{
"Exploitation": "poc"
},
{
"Automatable": "yes"
},
{
"Technical Impact": "total"
}
],
"role": "CISA Coordinator",
"timestamp": "2026-11-09T13:20:03.819595Z",
"version": "2.0.3"
},
"type": "ssvc"
}
}
],
"providerMetadata": {
"dateUpdated": "2026-11-09T13:20:31.168Z",
"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
"shortName": "CISA-ADP"
},
"references": [
{
"tags": [
"exploit"
],
"url": "https://github.com/Bubka/2FAuth/security/advisories/GHSA-mh8r-74x2-r457"
}
],
"title": "CISA ADP Vulnrichment"
}
],
"cna": {
"affected": [
{
"product": "2FAuth",
"vendor": "Bubka",
"versions": [
{
"status": "affected",
"version": "\u003c 8.0.0"
}
]
}
],
"descriptions": [
{
"lang": "en",
"value": "2FAuth is a web app to manage Two-Factor Authentication (2FA) accounts and generate their security codes. Prior to 8.0.0, when AUTHENTICATION_GUARD=reverse-proxy-guard is enabled, ReverseProxyGuard::user() reads the default REMOTE_USER identity header, or a custom identity header selected by the AUTH_PROXY_HEADER_FOR_USER configuration setting, without confirming that the request originated from a configured trusted proxy. A remote client that can reach the application directly can forge the selected identity header and authenticate as an existing user, including an administrator, gaining access to stored 2FA secrets and account or application management functions. This issue is fixed in version 8.0.0."
}
],
"metrics": [
{
"cvssV3_1": {
"attackComplexity": "LOW",
"attackVector": "NETWORK",
"availabilityImpact": "HIGH",
"baseScore": 9.8,
"baseSeverity": "CRITICAL",
"confidentialityImpact": "HIGH",
"integrityImpact": "HIGH",
"privilegesRequired": "NONE",
"scope": "UNCHANGED",
"userInteraction": "NONE",
"vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
"version": "3.1"
}
}
],
"problemTypes": [
{
"descriptions": [
{
"cweId": "CWE-287",
"description": "CWE-287: Improper Authentication",
"lang": "en",
"type": "CWE"
}
]
}
],
"providerMetadata": {
"dateUpdated": "2026-11-06T20:22:31.651Z",
"orgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
"shortName": "GitHub_M"
},
"references": [
{
"name": "https://github.com/Bubka/2FAuth/security/advisories/GHSA-mh8r-74x2-r457",
"tags": [
"x_refsource_CONFIRM"
],
"url": "https://github.com/Bubka/2FAuth/security/advisories/GHSA-mh8r-74x2-r457"
},
{
"name": "https://github.com/Bubka/2FAuth/commit/43873cbfba445926c7008b4291eeee67752af9e8",
"tags": [
"x_refsource_MISC"
],
"url": "https://github.com/Bubka/2FAuth/commit/43873cbfba445926c7008b4291eeee67752af9e8"
},
{
"name": "https://github.com/Bubka/2FAuth/releases/tag/v8.0.0",
"tags": [
"x_refsource_MISC"
],
"url": "https://github.com/Bubka/2FAuth/releases/tag/v8.0.0"
}
],
"source": {
"advisory": "GHSA-mh8r-74x2-r457",
"discovery": "UNKNOWN"
},
"title": "2FAuth: Reverse Proxy Guard Trusts Client-Supplied Headers Without Proxy Verification"
}
},
"cveMetadata": {
"assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
"assignerShortName": "GitHub_M",
"cveId": "CVE-2026-63439",
"datePublished": "2026-11-06T20:22:31.651Z",
"dateReserved": "2026-07-16T19:35:57.767Z",
"dateUpdated": "2026-11-09T13:20:36.761Z",
"state": "PUBLISHED"
},
"dataType": "CVE_RECORD",
"dataVersion": "5.2"
}
}
}
Loading…
Loading…
Drag nodes to arrange them. Double-click a related vulnerability to open it, or a source to visit its link. The Physics button on the left tunes the layout and the simulation; the legend at the bottom left hides or shows nodes by kind and by sighting type.
Experimental. This forecast is provided for visualization only and may change without notice. Do not use it for operational decisions.
Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
Vulnerability timeline
Sightings and recorded dates, grouped by day · UTC
Loading timeline…
Loading…
Loading…
The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the
vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base
model, served locally by ML-Gateway.
They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
Loading…
Related by attack behaviour
Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.