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Description

A reflected HTML injection vulnerability was identified in the GitHub Enterprise Server Management Console login page that could allow credential theft. The redirect_to query parameter on the /setup/unlock endpoint was reflected into an HTML attribute without proper sanitization, enabling an attacker to inject a form element that could capture administrator credentials. Exploitation required an administrator to click a crafted link and enter their credentials. This vulnerability affected GitHub Enterprise Server versions 3.19.1 through 3.19.5 and 3.20.0 through 3.20.1, and was fixed in versions 3.19.6 and 3.20.2. This vulnerability was reported via the GitHub Bug Bounty program.

PUBLISHED Reserved 2026-05-07 | Published 2026-05-07 | Updated 2026-05-08 | Assigner GitHub_P




MEDIUM: 5.9CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:A/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N

Problem types

CWE-79 Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

Product status

Default status
unaffected

3.19.1 (semver)
affected

3.20.0 (semver)
affected

3.19.0 (semver)
unaffected

3.21.0 (semver)
unaffected

Credits

maksyche finder

References

docs.github.com/...nterprise-server@3.19/admin/release-notes release-notes

docs.github.com/...nterprise-server@3.20/admin/release-notes release-notes

cve.org (CVE-2026-8106)

nvd.nist.gov (CVE-2026-8106)

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