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CVE-2026-77987 is a server-side request forgery vulnerability in the GitHub Enterprise Server notebook viewer affecting versions 3.17 through 3.22. The viewer validated the scheme and host of a user-supplied URL but failed to validate an explicitly specified port. An attacker could therefore cause the appliance to send requests to internal services bound to other ports on the same appliance. Although response bodies were not exposed, response-timing differences provided an oracle for extracting instance secrets character by character. Those secrets could subsequently be used against an internal service to obtain remote code execution on the appliance.
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No public exploit code observed for this vulnerability.
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8 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.
An SSRF vulnerability in GitHub Enterprise Server's notebook viewer that permits access to internal services on unvalidated ports. Timing-based response behavior can enable extraction of instance secrets, which can subsequently enable remote code execution through a separate internal-service interaction.
A critical GitHub Enterprise Server notebook viewer URL flaw that allowed explicit-port requests to reach co-located internal services. A response-timing oracle could enable extraction of instance secrets, potentially leading to remote code execution. Exploitation was unauthenticated when private mode was disabled, or required any authenticated user when private mode was enabled.
Query your assets running an affected version, and investigate the blast radius.
Every observed campaign linking this CVE to a named adversary.
Malware families riding this exploit, with evidence and IOCs.
YARA, Sigma, Snort, and vendor rules, auto-deployed to your SIEM.
Cross-references every affected SKU, including bundled OEM variants.
Community discussion across Reddit, Mastodon, and other social sources.