Is CVE-2026-4821 actively exploited?

No active exploitation of CVE-2026-4821 has been confirmed so far. Continue monitoring, as exploit status can change.

Can CVE-2026-4821 be exploited remotely?

No. CVE-2026-4821 requires local access to exploit.

What is the CVSS score of CVE-2026-4821?

CVE-2026-4821 has a CVSS score of 8.1 (HIGH).

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HIGH

CVE-2026-4821

CWE-78Published: April 21, 2026· Updated: Apr 22, 2026

8.1

CVSS v3.1

EPSS:0.01%probability of exploitation in 30 daysPercentile:2.6th

Official Description

An improper neutralization of special elements vulnerability was identified in GitHub Enterprise Server that allowed an authenticated Management Console administrator to execute arbitrary OS commands via shell metacharacter injection in proxy configuration fields such as http_proxy. Exploitation of this vulnerability required access to the GitHub Enterprise Server instance and administrator privileges to the Management Console. This vulnerability affected all versions of GitHub Enterprise Server prior to 3.21 and was fixed in versions 3.20.1, 3.19.5, 3.18.8, 3.17.14, 3.16.17, 3.15.21, 3.14.26. This vulnerability was reported via the GitHub Bug Bounty program.

NVD Source

Technical Analysis

CVE-2026-4821 requires local access, meaning attackers must already have a foothold on the target system.

Exploitation requires high privileges, which limits the exposure to scenarios where an attacker has already gained initial access.

CVSS v3.1 Vector Breakdown

Exploitability

Attack VectorLocal

Attack ComplexityLow

Privileges Req.High

User InteractionNone

ScopeX

Impact

Confidentiality

Integrity

Availability

CVSS:4.0/AV:L/AC:L/AT:N/PR:H/UI:N/VC:N/VI:H/VA:N/SC:N/SI:H/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X