Zen-C Vulnerable to Command Injection via Malicious Output Filename

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Summary

CVECVE-2026-28207
StatePUBLISHED
AssignerGitHub_M
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-02-26 23:16:35 UTC
Updated2026-05-01 14:38:16 UTC
DescriptionZen C is a systems programming language that compiles to human-readable GNU C/C11. Prior to version 0.4.2, a command injection vulnerability (CWE-78) in the Zen C compiler allows local attackers to execute arbitrary shell commands by providing a specially crafted output filename via the `-o` command-line argument. The vulnerability existed in the `main` application logic (specifically in `src/main.c`), where the compiler constructed a shell command string to invoke the backend C compiler. This command string was built by concatenating various arguments, including the user-controlled output filename, and was subsequently executed using the `system()` function. Because `system()` invokes a shell to parse and execute the command, shell metacharacters within the output filename were interpreted by the shell, leading to arbitrary command execution. An attacker who can influence the command-line arguments passed to the `zc` compiler (like through a build script or a CI/CD pipeline configuration) can execute arbitrary commands with the privileges of the user running the compiler. The vulnerability has been fixed in version 0.4.2 by removing `system()` calls, implementing `ArgList`, and internal argument handling. Users are advised to update to Zen C version v0.4.2 or later.

Risk And Classification

Primary CVSS: v3.1 7.3 HIGH from [email protected]

CVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:H

EPSS: 0.000150000 probability, percentile 0.032510000 (date 2026-05-05)

Problem Types: CWE-78 | CWE-78 CWE-78: Improper Neutralization of Special Elements used in an OS Command ('OS Command Injection')

VersionSourceTypeScoreSeverityVector
3.1[email protected]Primary7.3HIGHCVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:H
3.1[email protected]Secondary6.6MEDIUMCVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:L/I:H/A:L
3.1CNADECLARED6.6MEDIUMCVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:L/I:H/A:L

CVSS v3.1 Breakdown

Attack Vector
Local
Attack Complexity
Low
Privileges Required
Low
User Interaction
Required
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:H

NVD Known Affected Configurations (CPE 2.3)

TypeVendorProductVersionUpdateEditionLanguage
Application Zenc-lang Zen C All All All All

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Z-libs Zen-C affected < 0.4.2 Not specified

References

ReferenceSourceLinkTags
f0nduesav0yarde.github.io/blog/vulnerabilities/cve-2026-28207 af854a3a-2127-422b-91ae-364da2661108 f0nduesav0yarde.github.io Exploit, Third Party Advisory
github.com/z-libs/Zen-C/security/advisories/GHSA-9rff-x96h-76h2 134c704f-9b21-4f2e-91b3-4a467353bcc0 github.com Exploit, Mitigation, Vendor Advisory
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis
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