CVE-2026-77987 Details
A server-side request forgery (SSRF) vulnerability was identified in the notebook viewer of GitHub Enterprise Server. The notebook viewer validated the scheme and host of a user-supplied URL but did not validate the port, allowing requests to be directed to internal services listening on other ports of the same appliance. Response bodies were not returned to the requester, but response timing acted as an oracle that allowed instance secrets to be extracted character by character. An extracted secret could then be used in a separate interaction with an internal service to obtain remote code execution on the appliance. Exploitation required network access to the instance and was unauthenticated when private mode was disabled, or required any authenticated user when private mode was enabled. This vulnerability affected GitHub Enterprise Server versions 3.17 through 3.22 and was fixed in versions 3.22.1, 3.21.6, 3.20.8, 3.19.12, 3.18.15, and 3.17.21. This vulnerability was reported through the GitHub Bug Bounty program.
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Exploit prediction scoring system (EPSS) score for CVE-2026-77987
EPSS (Exploit Prediction Scoring System): EPSS predicts the likelihood that a vulnerability will be exploited in the wild. A higher percentage means a greater chance of an exploit occurring. The EPSS model produces a probability score between 0 and 1 (0 and 100%).
0.88 Probability of exploitation activity being observed over the next 30 days (58th percentile)
CVSS score for CVE-2026-77987
CVSS (Common Vulnerability Scoring System): An open framework owned and managed by FIRST.Org, Inc. that assigns a numerical score from 0 to 10 to software vulnerabilities to indicate their severity.
9.8 Critical
Products affected by CVE-2026-77987
Enterprise Server 3.20.0
Enterprise Server 3.20.1
Enterprise Server 3.20.2
Enterprise Server 3.21.0
Enterprise Server 3.17.3
DVE Score by Bitsight AI
DVE scores complement traditional static scoring systems like CVSS with Bitsight AI powered real-time threat intelligence and underground cyber criminal activity so that security teams can reduce alert fatigue and focus on vulnerabilities most likely to be exploited.
Low
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CVE-2026-77987 Global Footprint

Top 10 Identified Countries

Country Observations Percentage
US 54 58.70%
CA 8 8.70%
IE 6 6.52%
FR 5 5.43%
JP 4 4.35%
BE 3 3.26%
GB 3 3.26%
AU 2 2.17%
DE 2 2.17%
AE 1 1.09%

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CVE-2026-77987 Industry Footprint

Top 10 Identified Industries

*Service provider organizations (typically Technology and Telecommunications) are disproportionally represented in the results given their upstream ownership of end-user infrastructure. See our FAQs.

Industry* Observations Percentage
Technology 85 95.51%
Education 1 1.12%
Government/Politics 1 1.12%
Healthcare/Wellness 1 1.12%
Finance 1 1.12%

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