CVE-2026-4296 (GCVE-0-2026-4296)
Vulnerability from cvelistv5 – Published: 2026-04-21 22:12 – Updated: 2026-04-22 13:16
VLAI
EPSS
VEX
Title
Incorrect Regular Expression vulnerability in GitHub Enterprise Server allowed unauthorized access to user accounts via OAuth callback URL validation bypass
Summary
An incorrect regular expression vulnerability was identified in GitHub Enterprise Server that allowed an attacker to bypass OAuth redirect URI validation. An attacker with knowledge of a first-party OAuth application's registered callback URL could craft a malicious authorization link that, when clicked by a victim, would redirect the OAuth authorization code to an attacker-controlled domain. This could allow the attacker to gain unauthorized access to the victim's account with the scopes granted to the OAuth application. This vulnerability affected all versions of GitHub Enterprise Server prior to 3.21 and was fixed in versions 3.20.1, 3.19.5, 3.18.8, 3.17.14, 3.16.17, 3.15.21, 3.14.26. This vulnerability was reported via the GitHub Bug Bounty program.
Severity
SSVC
Exploitation: none
Automatable: no
Technical Impact: total
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-04-22 13:16 UTC
CWE
- CWE-185 - Incorrect Regular Expression
Assigner
References
7 references
| URL | Tags |
|---|---|
| https://docs.github.com/en/enterprise-server@3.14… | release-notes |
| https://docs.github.com/en/enterprise-server@3.15… | release-notes |
| https://docs.github.com/en/enterprise-server@3.16… | release-notes |
| https://docs.github.com/en/enterprise-server@3.17… | release-notes |
| https://docs.github.com/en/enterprise-server@3.18… | release-notes |
| https://docs.github.com/en/enterprise-server@3.19… | release-notes |
| https://docs.github.com/en/enterprise-server@3.20… | release-notes |
Impacted products
1 product
| Vendor | Product | Version | CPE status | |
|---|---|---|---|---|
| GitHub | Enterprise Server |
Affected:
3.14.0 , ≤ 3.14.25
(semver)
Affected: 3.15.0 , ≤ 3.15.20 (semver) Affected: 3.16.0 , ≤ 3.16.16 (semver) Affected: 3.17.0 , ≤ 3.17.13 (semver) Affected: 3.18.0 , ≤ 3.18.7 (semver) Affected: 3.19.0 , ≤ 3.19.4 (semver) Affected: 3.20.0 , < 3.20.1 (semver) |
guessed |
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"version": "3.15.0",
"versionType": "semver"
},
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"changes": [
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"at": "3.16.17",
"status": "unaffected"
}
],
"lessThanOrEqual": "3.16.16",
"status": "affected",
"version": "3.16.0",
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{
"changes": [
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"at": "3.17.14",
"status": "unaffected"
}
],
"lessThanOrEqual": "3.17.13",
"status": "affected",
"version": "3.17.0",
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},
{
"changes": [
{
"at": "3.18.8",
"status": "unaffected"
}
],
"lessThanOrEqual": "3.18.7",
"status": "affected",
"version": "3.18.0",
"versionType": "semver"
},
{
"changes": [
{
"at": "3.19.5",
"status": "unaffected"
}
],
"lessThanOrEqual": "3.19.4",
"status": "affected",
"version": "3.19.0",
"versionType": "semver"
},
{
"changes": [
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"at": "3.20.1",
"status": "unaffected"
}
],
"lessThan": "3.20.1",
"status": "affected",
"version": "3.20.0",
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}
]
}
],
"credits": [
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"lang": "en",
"type": "finder",
"value": "ahacker1"
},
{
"lang": "en",
"type": "finder",
"value": "hacktron"
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],
"descriptions": [
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"value": "An incorrect regular expression vulnerability was identified in GitHub Enterprise Server that allowed an attacker to bypass OAuth redirect URI validation. An attacker with knowledge of a first-party OAuth application\u0027s registered callback URL could craft a malicious authorization link that, when clicked by a victim, would redirect the OAuth authorization code to an attacker-controlled domain. This could allow the attacker to gain unauthorized access to the victim\u0027s account with the scopes granted to the OAuth application. This vulnerability affected all versions of GitHub Enterprise Server prior to 3.21 and was fixed in versions 3.20.1, 3.19.5, 3.18.8, 3.17.14, 3.16.17, 3.15.21, 3.14.26. This vulnerability was reported via the GitHub Bug Bounty program.\u003cbr\u003e"
}
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"value": "An incorrect regular expression vulnerability was identified in GitHub Enterprise Server that allowed an attacker to bypass OAuth redirect URI validation. An attacker with knowledge of a first-party OAuth application\u0027s registered callback URL could craft a malicious authorization link that, when clicked by a victim, would redirect the OAuth authorization code to an attacker-controlled domain. This could allow the attacker to gain unauthorized access to the victim\u0027s account with the scopes granted to the OAuth application. This vulnerability affected all versions of GitHub Enterprise Server prior to 3.21 and was fixed in versions 3.20.1, 3.19.5, 3.18.8, 3.17.14, 3.16.17, 3.15.21, 3.14.26. This vulnerability was reported via the GitHub Bug Bounty program."
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"impacts": [
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"metrics": [
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"exploitMaturity": "NOT_DEFINED",
"privilegesRequired": "LOW",
"providerUrgency": "NOT_DEFINED",
"subAvailabilityImpact": "NONE",
"subConfidentialityImpact": "NONE",
"subIntegrityImpact": "NONE",
"userInteraction": "PASSIVE",
"valueDensity": "NOT_DEFINED",
"vectorString": "CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N",
"version": "4.0",
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"vulnIntegrityImpact": "HIGH",
"vulnerabilityResponseEffort": "NOT_DEFINED"
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"format": "CVSS",
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"description": "CWE-185 Incorrect Regular Expression",
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"providerMetadata": {
"dateUpdated": "2026-04-21T22:12:45.356Z",
"orgId": "82327ea3-741d-41e4-88f8-2cf9e791e760",
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"url": "https://docs.github.com/en/enterprise-server@3.15/admin/release-notes#3.15.21"
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"url": "https://docs.github.com/en/enterprise-server@3.16/admin/release-notes#3.16.17"
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"url": "https://docs.github.com/en/enterprise-server@3.17/admin/release-notes#3.17.14"
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"url": "https://docs.github.com/en/enterprise-server@3.18/admin/release-notes#3.18.8"
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{
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"url": "https://docs.github.com/en/enterprise-server@3.19/admin/release-notes#3.19.5"
},
{
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"url": "https://docs.github.com/en/enterprise-server@3.20/admin/release-notes#3.20.1"
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],
"source": {
"discovery": "UNKNOWN"
},
"title": "Incorrect Regular Expression vulnerability in GitHub Enterprise Server allowed unauthorized access to user accounts via OAuth callback URL validation bypass",
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},
"cveMetadata": {
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"assignerShortName": "GitHub_P",
"cveId": "CVE-2026-4296",
"datePublished": "2026-04-21T22:12:45.356Z",
"dateReserved": "2026-03-16T17:48:03.040Z",
"dateUpdated": "2026-04-22T13:16:53.004Z",
"state": "PUBLISHED"
},
"dataType": "CVE_RECORD",
"dataVersion": "5.2"
}
}
}
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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
How durations are calculated
Following the VTEM framework (Black Hat USA 2015), time to patch starts when the vendor or a coordinator was informed, total time to patch at discovery, and disclosure to patch at public disclosure; vendor response time runs from the report to its acknowledgement. Time to exploit and time unpatched start at the earliest discovery or report, falling back to public disclosure. Unpatched time ends at the first recorded patch, or the calculation time when no patch is recorded. Exploitation to patch shows the interval between those two events; a published proof of concept is a public exploit, not exploitation.
Each result shows its source dates. A negative interval means the end event came first; when date-only inputs leave the order open, the result says so. Date-only inputs are approximate. The earliest evidence wins: KEV report dates and sightings are labelled as such. Records describing another vulnerability are listed but never calculated from, and a PoC alone does not establish exploitation. Missing patch evidence does not prove that no patch exists. Filters below change the event list only.
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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.
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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.