CVE-2026-26833

CriticalPublic PoCRCE

Published: 25 March 2026

Published

25 March 2026

Modified

30 March 2026

KEV Added

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Patch

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CVSS Score 9.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

EPSS Score 0.0047 64.9th percentile

Risk Priority 20 60% EPSS · 20% KEV · 20% CVSS

Summary

CVE-2026-26833 is a critical-severity OS Command Injection (CWE-78) vulnerability in Mmahrous Thumbler. Its CVSS base score is 9.8 (Critical).

Operationally, exploitation aligns with the MITRE ATT&CK technique Exploit Public-Facing Application (T1190); ranked in the top 35.1% of CVEs by exploit likelihood; it is not currently listed in the CISA KEV catalog; a public proof-of-concept is referenced.

The strongest mitigations our analysis identified are NIST 800-53 RA-5 (Vulnerability Monitoring and Scanning) and SI-10 (Information Input Validation).

Threat & Defense at a Glance

What attackers do: exploitation maps to Exploit Public-Facing Application (T1190) and 1 other technique. What defenders deploy: see the NIST 800-53 controls recommended below.

Threat & Defense Details

Mitigating Controls (NIST 800-53 r5)AI

SI-10 Information Input Validation good match

prevent

SI-10 directly prevents OS command injection by requiring validation and sanitization of user-supplied input, output, time, and size parameters before concatenation into shell commands executed by child_process.exec().

SI-2 Flaw Remediation good match

prevent

SI-2 mandates timely identification, reporting, and correction of flaws like this command injection vulnerability in the thumbler package through patching to version beyond 1.1.2.

RA-5 Vulnerability Monitoring and Scanning good match

detect

RA-5 requires vulnerability scanning of software dependencies like the thumbler npm package to detect CVE-2026-26833 and trigger remediation.

MITRE ATT&CK Enterprise TechniquesAI

T1190 Exploit Public-Facing Application Initial Access

Adversaries may attempt to exploit a weakness in an Internet-facing host or system to initially access a network.

attack.mitre.org →

T1059.004 Unix Shell Execution

Adversaries may abuse Unix shell commands and scripts for execution.

attack.mitre.org →

Why these techniques?

CVE enables remote unauthenticated OS command injection via unsanitized parameters in child_process.exec(), facilitating exploitation of public-facing applications (T1190) and Unix Shell command execution (T1059.004).

Confidence: HIGH · MITRE ATT&CK Enterprise v19.0

NVD Description

thumbler through 1.1.2 allows OS command injection via the input, output, time, or size parameter in the thumbnail() function because user input is concatenated into a shell command string passed to child_process.exec() without proper sanitization or escaping.

Deeper analysisAI

CVE-2026-26833 is an OS command injection vulnerability affecting the thumbler npm package through version 1.1.2. The flaw occurs in the thumbnail() function within lib/thumbler.js, where user-supplied values for the input, output, time, or size parameters are concatenated directly into a shell command string passed to child_process.exec() without sanitization or escaping. This issue corresponds to CWE-78 (Improper Neutralization of Special Elements used in an OS Command) and CWE-94 (Improper Control of Generation of Code), earning a CVSS v3.1 base score of 9.8 (AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H).

A remote, unauthenticated attacker can exploit this vulnerability over the network with low complexity and no user interaction required. By supplying malicious payloads in the affected parameters, the attacker can inject arbitrary OS commands, leading to remote code execution on the host system. Exploitation could result in high-impact compromise, including unauthorized data access, modification, or disruption of the affected application.

Mitigation details and patches can be found in the referenced advisories, including the thumbler GitHub repository (https://github.com/mmahrous/thumbler), source code (https://github.com/mmahrous/thumbler/blob/master/lib/thumbler.js), dedicated CVE repository (https://github.com/zebbernCVE/CVE-2026-26833), and npm package page (https://www.npmjs.com/package/thumbler). The vulnerability was published on 2026-03-25.