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Fencer Vulns
medium 6.6

CVE-2026-28207 json

Zen-C Vulnerable to Command Injection via Malicious Output Filename

published 2026-02-26 8 mo ago modified 2026-06-17 4 mo ago also EUVD-2026-8908

cvss
6.6
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
1.1%
EPSS 1.1% chance of exploitation in 30 days, percentile 65%
public exploits
0
none known

Summary

Zen 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.

Patch / fix

  • zenc-lang zen_c 0.4.2

CISA SSVC

Exploitation
Proof of concept is public
Automatable
no
Technical impact
partial
Assessed
8 mo ago

Exploit prediction

1.08% chance of exploitation in the next 30 days, higher than 65% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • github.com https://github.com/z-libs/Zen-C/security/advisories/GHSA-9rff-x96h-76h2 referenced PoC, tagged "exploit" by a source, unverified
  • f0nduesav0yarde.github.io https://f0nduesav0yarde.github.io/blog/vulnerabilities/cve-2026-28207/ referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CNA 3.1 6.6 CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:L/I:H/A:L
NVD 3.1 7.3 CVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:H

Affected products

  • z-libs Zen-C

Classification

Weakness
  • CWE-78 Improper Neutralization of Special Elements used in an OS 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.