CVE-2026-17556 Details
A path traversal vulnerability was identified in GitHub Enterprise Server that allowed an unauthenticated attacker to delete arbitrary files and directories on the instance, including the entire user storage directory containing Git LFS objects, release assets, attachments, and avatars. The X-GitHub-Request-Id request header was used without sanitization as a filesystem path segment for the upload buffer directory, so a traversal value pointed the buffer at an arbitrary path and the deferred cleanup routine recursively removed the traversed target. Exploitation required only network reachability to the instance and no authentication, and it worked even when private mode was enabled. This vulnerability affected all versions of GitHub Enterprise Server prior to 3.22 and was fixed in versions 3.21.4, 3.20.6, 3.19.10, 3.18.13 and 3.17.19. This vulnerability was reported via the GitHub Bug Bounty program.
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Exploit prediction scoring system (EPSS) score for CVE-2026-17556
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%).
0.5 Probability of exploitation activity being observed over the next 30 days (41th percentile)
CVSS score for CVE-2026-17556
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.
9.1 Critical
Products affected by CVE-2026-17556
Enterprise Server 3.12.7
Enterprise Server 3.14.11
Enterprise Server 3.15.12
Enterprise Server 3.8.0
Enterprise Server 3.13.6
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-2026-17556 Global Footprint

Top 10 Identified Countries

Country Observations Percentage
US 114 58.16%
IE 14 7.14%
AU 12 6.12%
CA 11 5.61%
GB 9 4.59%
JP 6 3.06%
SG 6 3.06%
FR 5 2.55%
NL 5 2.55%
IN 3 1.53%

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CVE-2026-17556 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 177 93.16%
Education 8 4.21%
Government/Politics 2 1.05%
Business Services 2 1.05%
Telecommunications 1 0.53%

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