CVE-2020-10518 | Unsafe configuration options in GitHub Pages leading to remote code execution on GitHub Enterprise Server

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.

Published: 2020-08-27 Last update: 2026-06-16 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2020-10518 is rated High Risk (66.6/100): CVSS High severity, with medium exploitation likelihood (EPSS 3.70%). High exploitation likelihood—assess exposure and prioritize remediation.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2020-10518

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-06-15 3.15% 3.70% +0.55%
2 2026-03-04 3.04% 3.15% +0.11%
3 2026-03-01 — 3.04% —

Full EPSS history (35 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2020-10518

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
8.8 3.1 HIGH
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:L)
A normal user session is enough; they don’t have to be admin.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:H)
Serious risk that confidential data gets exposed in a big way.
Integrity (I:H)
They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 2.8 5.9 [email protected]
6.5 2.0 MEDIUM
AV:N/AC:L/Au:S/C:P/I:P/A:P Click to expand
Access vector (AV:N)
Can be exploited remotely over network reachability.
Access complexity (AC:L)
Exploitation conditions are straightforward and predictable.
Authentication (AU:S)
A single authentication is required.
Confidentiality impact (C:P)
Partial confidentiality impact.
Integrity impact (I:P)
Partial integrity impact.
Availability impact (A:P)
Partial availability impact.
 8.0 6.4 [email protected]

Weakness enumeration for CVE-2020-10518

Affected software / configurations for CVE-2020-10518

Vendor Product Version Raw CPE
github github < 2.19.21 cpe:2.3:a:github:github:*:*:*:*:enterprise:*:*:*
github github >= 2.20.0, < 2.20.15 cpe:2.3:a:github:github:*:*:*:*:enterprise:*:*:*
github github >= 2.21.0, < 2.21.6 cpe:2.3:a:github:github:*:*:*:*:enterprise:*:*:*

References for CVE-2020-10518

cvelogic Threat Intelligence