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Malcolm CVE-2026-55676

| EUVDEUVD-2026-56948 HIGH
Unrestricted Upload of File with Dangerous Type (CWE-434)
2026-08-11 GitHub_M
8.8
CVSS 3.1 · Vendor: GitHub_M
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Severity by source

Vendor (GitHub_M) PRIMARY
8.8 HIGH
AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
vuln.today AI
8.8 HIGH

PR:L confirmed by ROLE_UPLOAD authentication requirement; S:U because execution is confined to www-data in the file-upload container with no cross-container scope change.

3.1 AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
4.0 AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N

Primary rating from Vendor (GitHub_M).

CVSS VectorVendor: GitHub_M

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Attack Vector
Network
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

Lifecycle Timeline

4
Source Code Evidence Fetched
Aug 11, 2026 - 21:36 vuln.today
Analysis Generated
Aug 11, 2026 - 21:36 vuln.today
Patch available
Aug 11, 2026 - 21:18 EUVD
CVE Published
Aug 11, 2026 - 20:24 cve.org
HIGH 8.8

DescriptionCVE.org

Malcolm is a network traffic analysis tool suite. The file-upload component (FilePond PHP backend) accepts uploads at POST /server/php/submit.php and stores them in a directory served by the same nginx and php-fpm instance. The allow-list that should restrict accepted file types is an empty array by default (file-upload/php/config.php:16), so the type check is a no-op and every extension is accepted. The filename sanitizer keeps the .php extension intact. Committed files land in /var/www/upload/server/php/files (file-upload/php/config.php:7), and the component's nginx routes any URL ending in .php to php-fpm. An authenticated GET /server/php/files/<name>.php then executes the uploaded code as www-data. Prior to version 26.06.1, in RBAC mode, the upload endpoint is reachable by the granular ROLE_UPLOAD role (nginx/lua/nginx_auth_helpers.lua:71), a role intended only for submitting capture files. As a result, a user holding the upload-only role runs arbitrary PHP as www-data inside the file-upload container. Version 26.06.1 fixes the issue.

AnalysisAI

Remote code execution in Malcolm (cisagov) prior to version 26.06.1 allows an authenticated user holding the ROLE_UPLOAD role to upload arbitrary PHP files through the FilePond file-upload component and trigger their server-side execution. The file-type allowlist in file-upload/php/config.php is an empty array by default, making the type check a no-op; the filename sanitizer further preserves the .php extension intact, and nginx routes any URL terminating in .php to php-fpm. …

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Attack ChainAIDerived

Hypothetical attack flow derived from CVE metadata

Access
Obtain valid ROLE_UPLOAD credentials
Delivery
POST PHP webshell to /server/php/submit.php
Exploit
File stored with .php extension intact in web root
Execution
Issue authenticated GET to /server/php/files/<name>.php
Persist
nginx routes .php URI to php-fpm
Impact
Arbitrary PHP executes as www-data in file-upload container

Vulnerability AssessmentAI

Exploitation Exploitation requires a valid Malcolm user account with the ROLE_UPLOAD RBAC role explicitly assigned - this role is intended for submitting network capture files and is meaningfully distinct from administrator roles, but may be granted broadly to analysts or automated ingest pipelines. … Additional conditions and limiting factors are described in the full assessment.
Risk Assessment The CVSS 8.8 score (AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H) is well-calibrated and not inflated: the attack path is mechanical - upload a PHP file, GET it - and requires only low-privilege authentication rather than no authentication. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in.
Exploit Scenario An attacker with a Malcolm account holding the ROLE_UPLOAD RBAC role submits a PHP webshell (e.g., a file named `shell.php` containing `<?php system($_GET['cmd']); ?>`) via an authenticated POST to `/server/php/submit.php`; the server stores the file at `/var/www/upload/server/php/files/shell.php` without stripping the extension. The attacker then issues an authenticated GET to `/server/php/files/shell.php?cmd=id`, nginx routes the request to php-fpm, and the webshell executes as `www-data` inside the file-upload container, granting interactive command execution. …
Remediation Upgrade to Malcolm v26.06.1, which directly resolves the unrestricted PHP upload path per the vendor advisory at https://github.com/cisagov/Malcolm/security/advisories/GHSA-8cvp-m7pg-qrp7 and the release at https://github.com/cisagov/Malcolm/releases/tag/v26.06.1. … Detailed patch versions, workarounds, and compensating controls in full report.

Recommended ActionAI

Within 24 hours, identify all Malcolm deployments and determine which run versions prior to 26.06.1, then confirm role-based access control (RBAC) enablement on each instance. …

Sign in for detailed remediation steps and compensating controls.

Threat intelligence, references, and detailed analysis are available after sign-in.

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CVE-2026-55676 vulnerability details – vuln.today

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