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File Browser: Cross-user unauthorized share-link deletion via unbounded prefix match in DeleteWithPathPrefix

High severity GitHub Reviewed Published Jun 3, 2026 in filebrowser/filebrowser

Package

gomod github.com/filebrowser/filebrowser (Go)

Affected versions

<= 1.11.0

Patched versions

None
gomod github.com/filebrowser/filebrowser/v2 (Go)
<= 2.63.5
2.63.6

Description

Summary

A low-privileged authenticated user of filebrowser (with create + delete permissions in their own isolated scope) can silently destroy share-link records belonging to any other user — including the administrator — by performing a legitimate DELETE on a file in their own directory whose logical path happens to be a byte-prefix of another user's stored share.Link.Path. The file contents of the victim are not exposed, but the victim's share links are irrevocably wiped.

Details

resourceDeleteHandler in http/resource.go cleans up any share records that reference a deleted file by calling:

// http/resource.go
err = d.store.Share.DeleteWithPathPrefix(file.Path)

file.Path here is the logical path from the URL of the deleting user's request (e.g. /a), not the absolute filesystem path. It is passed as-is to the bolt backend:

// storage/bolt/share.go
func (s shareBackend) DeleteWithPathPrefix(pathPrefix string) error {
    var links []share.Link
    if err := s.db.Prefix("Path", pathPrefix, &links); err != nil {
        return err
    }
    for _, link := range links {
        err = errors.Join(err, s.db.DeleteStruct(&share.Link{Hash: link.Hash}))
    }
    return err
}

Why the design contradicts this behavior. share.Link carries a UserID field and the application elsewhere treats shares as per-user owned resources. shareDeleteHandler explicitly enforces link.UserID != d.user.ID && !d.user.Perm.Admin → 403. The file-deletion side-effect path is the only location that bypasses this rule.

Impact

  • Integrity: unauthorized deletion of share-link metadata belonging to arbitrary users, including administrators.
  • Availability: effective denial-of-service of the share-link feature — a cooperating (or malicious) low-priv user can wipe the bulk of existing share links by iterating a short set of one- and two-character prefixes.

References

@hacdias hacdias published to filebrowser/filebrowser Jun 3, 2026
Published to the GitHub Advisory Database Jun 12, 2026
Reviewed Jun 12, 2026

Severity

High

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 None
Integrity High
Availability High
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:N/VI:H/VA:H/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.
(5th percentile)

Weaknesses

Authorization Bypass Through User-Controlled Key

The system's authorization functionality does not prevent one user from gaining access to another user's data or record by modifying the key value identifying the data. Learn more on MITRE.

CVE ID

CVE-2026-54097

GHSA ID

GHSA-5ww9-jg6q-38r7

Source code

Credits

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