CVE-2026-1355: Missing Authorization Check in GitHub Enterprise Server Allows Unauthorized Uploads to Repository Migration Exports
A Missing Authorization vulnerability was identified in GitHub Enterprise Server that allowed an attacker to upload unauthorized content to another user’s repository migration export due to a missing authorization check in the repository migration upload endpoint. By supplying the migration identifier, an attacker could overwrite or replace a victim’s migration archive, potentially causing victims to download attacker-controlled repository data during migration restores or automated imports. An attacker would require authentication to the victim's GitHub Enterprise Server instance. This vulnerability affected all versions of GitHub Enterprise Server prior to 3.20 and was fixed in versions 3.19.2, 3.18.5, 3.17.11, 3.16.14, 3.15.18, 3.14.23. This vulnerability was reported via the GitHub Bug Bounty program.
Affected Software
Event History
Frequently Asked Questions
What is the severity of CVE-2026-1355?
CVE-2026-1355 is considered a critical severity vulnerability due to its potential to allow unauthorized content uploads.
How do I fix CVE-2026-1355?
To fix CVE-2026-1355, upgrade GitHub Enterprise Server to version 3.21 or later where the missing authorization vulnerability has been addressed.
What products are affected by CVE-2026-1355?
CVE-2026-1355 affects GitHub Enterprise Server versions prior to 3.21, specifically versions up to and including 3.20.
What type of vulnerability is CVE-2026-1355?
CVE-2026-1355 is classified as a Missing Authorization vulnerability.
What can an attacker do with CVE-2026-1355?
An attacker exploiting CVE-2026-1355 can upload unauthorized content to another user's repository migration export.