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Description

A Server-Side Request Forgery (SSRF) vulnerability was identified in GitHub Enterprise Server that allowed an attacker to cause the server to issue HTTP requests to internal services via the security advisories package lookup feature. By directing requests to an internal management service and measuring response timing, an attacker could infer the values of sensitive environment variables, including signing secrets and private keys. Exploitation required GitHub Packages to be enabled; on instances not running in private mode the vulnerability was exploitable without authentication, otherwise any authenticated user could exploit it. This vulnerability affected all versions of GitHub Enterprise Server prior to 3.21.1 and was fixed in versions 3.20.3, 3.19.7, 3.18.10, 3.17.16, and 3.16.19. This vulnerability was reported via the GitHub Bug Bounty program.

PUBLISHED Reserved 2026-05-14 | Published 2026-05-26 | Updated 2026-05-27 | Assigner GitHub_P




HIGH: 7.0CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:L/VI:N/VA:N/SC:H/SI:H/SA:N

Problem types

CWE-918 Server-Side request forgery (SSRF)

Product status

Default status
unaffected

3.21.0 (semver) before 3.21.1
affected

3.20.0 (semver)
affected

3.19.0 (semver)
affected

3.18.0 (semver)
affected

3.17.0 (semver)
affected

3.16.0 (semver)
affected

Credits

R31n finder

References

docs.github.com/...nterprise-server@3.21/admin/release-notes release-notes

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

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

docs.github.com/...nterprise-server@3.18/admin/release-notes release-notes

docs.github.com/...nterprise-server@3.17/admin/release-notes release-notes

docs.github.com/...nterprise-server@3.16/admin/release-notes release-notes

cve.org (CVE-2026-8606)

nvd.nist.gov (CVE-2026-8606)

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