CVE-2026-4296Network attack vector

Account takeover via OAuth callback regex bypass

Published Apr 21, 2026 · Updated Apr 21, 2026

OAuth redirect validation in GitHub Enterprise Server allows attackers to steal a victim's authorization code through a crafted link. Incorrect regular expression matching in the callback URL validator accepts an attacker-controlled domain as if it matched the registered callback. Exploitation requires knowledge of a registered first-party callback URL and a victim click; resulting account access is limited to the OAuth application's scopes.

CVSS severity7.5
High
EPSS probability0.43%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

OAuth redirect validation in GitHub Enterprise Server allows attackers to steal a victim's authorization code through a crafted link. Incorrect regular expression matching in the callback URL validator accepts an attacker-controlled domain as if it matched the registered callback. Exploitation requires knowledge of a registered first-party callback URL and a victim click; resulting account access is limited to the OAuth application's scopes.

The record

CVE
CVE-2026-4296
Published
Apr 21, 2026
Updated
Apr 21, 2026
Vendor
Twitter
Product
GitHub Enterprise Server
Classifications
CWE-185, T1528
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Apr 21, 2026CVE publishedPublication date reported by the CVE source.
  2. Apr 21, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=3.14.0 <=3.14.25 changes=[{"at":"3.14.26","status":"unaffected"}]
  2. Affected versionversion=3.15.0 <=3.15.20 changes=[{"at":"3.15.21","status":"unaffected"}]
  3. Affected versionversion=3.16.0 <=3.16.16 changes=[{"at":"3.16.17","status":"unaffected"}]
  4. Affected versionversion=3.17.0 <=3.17.13 changes=[{"at":"3.17.14","status":"unaffected"}]
  5. Affected versionversion=3.18.0 <=3.18.7 changes=[{"at":"3.18.8","status":"unaffected"}]
  6. Affected versionversion=3.19.0 <=3.19.4 changes=[{"at":"3.19.5","status":"unaffected"}]
  7. Affected versionversion=3.20.0 <3.20.1 changes=[{"at":"3.20.1","status":"unaffected"}]

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Twitter · GitHub Enterprise Serverversion=3.14.0 <=3.14.25 changes=[{"at":"3.14.26","status":"unaffected"}]; version=3.15.0 <=3.15.20 changes=[{"at":"3.15.21","status":"unaffected"}]; version=3.16.0 <=3.16.16 changes=[{"at":"3.16.17","status":"unaffected"}]; version=3.17.0 <=3.17.13 changes=[{"at":"3.17.14","status":"unaffected"}]; version=3.18.0 <=3.18.7 changes=[{"at":"3.18.8","status":"unaffected"}]; version=3.19.0 <=3.19.4 changes=[{"at":"3.19.5","status":"unaffected"}]; version=3.20.0 <3.20.1 changes=[{"at":"3.20.1","status":"unaffected"}]

Published CVSS scores

7.5GitHub, Inc.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
8.8NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-185Incorrect Regular Expression
T1528Steal Application Access Token

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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