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Fencer Vulns
high 8.8

CVE-2020-10518 json

Unsafe configuration options in GitHub Pages leading to remote code execution on GitHub Enterprise Server

published 2020-08-27 6 y ago modified 2026-06-17 4 mo ago also EUVD-2020-2971

cvss
8.8
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
3.7%
EPSS 3.7% chance of exploitation in 30 days, percentile 89%
public exploits
0
none known

Summary

A remote code execution vulnerability was identified in GitHub Enterprise Server that could be exploited when building a GitHub Pages site. User-controlled configuration of the underlying parsers used by GitHub Pages were not sufficiently restricted and made it possible to execute commands on the GitHub Enterprise Server instance. To exploit this vulnerability, an attacker would need permission to create and build a GitHub Pages site on the GitHub Enterprise Server instance. This vulnerability affected all versions of GitHub Enterprise Server prior to 2.22 and was fixed in 2.21.6, 2.20.15, and 2.19.21. The underlying issues contributing to this vulnerability were identified both internally and through the GitHub Security Bug Bounty program.

Patch / fix

  • GitHub GitHub Enterprise Server 2.19.21, 2.20.15, 2.21.6

Exploit prediction

3.70% chance of exploitation in the next 30 days, higher than 89% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
NVD 3.1 8.8 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
NVD 2.0 6.5 AV:N/AC:L/Au:S/C:P/I:P/A:P

Affected products

  • GitHub GitHub Enterprise Server

Classification

Weakness
  • CWE-77 Improper Neutralization of Special Elements used in a Command

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.