Vulnerability-Lookup

CVE-2026-55499 (GCVE-0-2026-55499)

Vulnerability from cvelistv5 – Published: 2026-07-31 03:34 – Updated: 2026-07-31 23:15

Title

Cloudreve: Broken access control in file event stream leaks activity events for unshared siblings to single-file share recipients

Summary

Cloudreve is a self-hosted file management and sharing system. Prior to 4.17.0, a single-file share event-stream subscription resolves the share root to the owner’s parent folder and subscribes to that folder topic, allowing an authenticated share recipient to receive names, paths, rename targets, event types, and hashed identifiers for unshared sibling files and folders. This issue is fixed in version 4.17.0.

Severity

4.3 (Medium)


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

SSVC

Exploitation: poc Automatable: no Technical Impact: partial

CISA Coordinator (v2.0.3)

CWE

CWE-863 - Incorrect Authorization

Assigner

GitHub_M

References

3 references

URL	Tags
https://github.com/cloudreve/cloudreve/security/a…	x_refsource_CONFIRM
https://github.com/cloudreve/cloudreve/commit/0b0…	x_refsource_MISC
https://github.com/cloudreve/cloudreve/releases/t…	x_refsource_MISC

Impacted products

1 product

Vendor	Product	Version
cloudreve	cloudreve	Affected: < 4.17.0

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GHSA-W8X7-H2PX-XMQ8

Vulnerability from github – Published: 2026-07-24 20:49 – Updated: 2026-07-24 20:49

Summary

Cloudreve: Broken Access Control in file event stream: a single-file share recipient is subscribed to the owner's parent folder and receives activity events for unshared siblings

Details

Summary

When an authenticated recipient of a single-file share opens the file event stream (GET /api/v4/file/events?uri=<share-root>), Cloudreve validates the URI by listing it and then subscribes the caller to parent.ID(). For a single-file share, the share navigator resolves the bare share-root URI to the owner-side parent folder of the shared file (not the file), while the visible listing is filtered down to just the shared file. The event hub then keys topics by numeric file ID only and, on each file change, fans the event out to subscribers of every ancestor topic, filtering only the client ID that caused the event — never the subscriber's share scope.

Consequently, a recipient of one shared file can receive Server-Sent Events (type, sibling path/name, rename target, hashed file ID) for other files and subfolders in the owner's parent folder that were never shared. Contents are not disclosed; file-activity metadata is.

Details

Root cause (verified at `26b6b10`)

1. Events route — authenticated, feature-flagged, no share-scope check (routers/router.go):

file := v4.Group("file"); file.Use(middleware.RequiredScopes(types.ScopeFilesRead))
file.GET("events",
    middleware.LoginRequired(),
    middleware.IsFunctionEnabled(func(c *gin.Context) bool { return dep.SettingProvider().EventHubEnabled(c) }),
    controllers.FromQuery[explorer.ExplorerEventService](...), controllers.HandleExplorerEventsPush)

EventHubEnabled defaults true (inventory/setting.go: "fs_event_push_enabled":"1").

2. Service subscribes to the listed parent's ID (service/explorer/events.go):

parent, _, err := m.List(c, uri, &manager.ListArgs{Page:0, PageSize:1})   // also runs share validity/password
...
rx, resumed, err := eventHub.Subscribe(c, parent.ID(), requestInfo.ClientID)

3. Single-file share Root swaps the share root to the owner parent (share_navigator.go):

n.shareRoot = newFile(nil, share.Edges.File)
...
if n.shareRoot.Type() == types.FileTypeFile {
    n.singleFileShare = true
    n.shareRoot = n.shareRoot.Parent   // <-- owner-side parent folder
}

4. To returns that parent for the bare root URI (share_navigator.go):

elements := path.Elements()
if len(elements) == 1 && n.singleFileShare { return latestSharedSingleFile(...) } // only when URI names the file
...
return current  // current == shareRoot == owner parent folder

The bare root share URI has zero path elements (URI.Elements() returns nil for path /), so the len(elements)==1 guard is skipped and To returns the parent folder. dbfs.List returns that as parent, so parent.ID() is the owner parent folder's real ID.

5. Children masks the broader parent — for singleFileShare it returns only []*File{sharedFile}, so the recipient's listing shows just the shared file even though the subscribed topic is the whole parent.

6. Publication fans out to ancestor topics with only a client-ID filter (dbfs/events.go):

func (f *DBFS) getEligibleSubscriber(ctx, file, checkParentPerm) []foundSubscriber {
    roots := file.Ancestors()
    for _, root := range roots {
        subscribers := f.eventHub.GetSubscribers(ctx, root.Model.ID)
        subscribers = lo.Filter(subscribers, func(s eventhub.Subscriber, _ int) bool {
            return !(requestInfo != nil && s.ID() == requestInfo.ClientID)  // ONLY exclude the causing client
        })
        ...
    }
}
// emit*: From: subscriber.relativePath(file)  // owner-side path of the changed sibling

relativePath trims the changed file's owner path by the subscribed root's owner path, yielding the sibling's name (e.g. /Secret-Plan.pdf). No check that the subscriber is authorized for the changed file or within their share scope.

Validation performed

Independent validation against commit 26b6b10 in a clean sandbox.

Source-verified (static): all of (1)–(6) confirmed verbatim, including the negative direction (an explicit …/shared.txt URI resolves to the file, and oss/qiniu-style flows are irrelevant here).

Dynamic (control-flow executed): the full binary is not buildable offline (modules behind an unreachable proxy, embedded frontend, DB/eventhub). The reseacher ran two harnesses: - A net/url-based check of the linchpin — the bare root share URI yields 0 path elements (so To returns the parent), while …/shared.txt yields 1 (returns the file). This is the subtle point on which the whole finding turns, and it holds. - A model of Root/To/getEligibleSubscriber/relativePath driving the end-to-end flow:

[1] single-file share root URI -> m.List parent = "docs" (id 10), NOT shared.txt (id 11)  -> subscribed to owner parent
[2] owner renames /docs/Secret-Plan.pdf -> client 'attacker' receives: from="/Secret-Plan.pdf" file_id=12 (topic 10)
[3] CONTROL: event caused by attacker's own client id -> suppressed (the only filter)
[4] CONTROL: explicit URI 'shared.txt' -> resolves to file (id 11) -> no sibling events

Steps to reproduce

Owner shares a single file shared.txt from /docs, which also contains Secret-Plan.pdf.
Recipient (logged-in, Files.Read, with the share password if any) opens the event stream on the share root: GET /api/v4/file/events?uri=cloudreve%3A%2F%2F<share-id>%40share Cookie: cloudreve-session=<recipient-session> X-Cr-Client-Id: <uuid> Accept: text/event-stream
Owner creates/renames/modifies/moves/deletes Secret-Plan.pdf.
The recipient's stream receives, e.g.: event: event data: {"type":"rename","file_id":"<hashed>","from":"/Secret-Plan.pdf","to":"/Secret-Plan-v2.pdf"}

Expected: the recipient only receives events for the shared file. Actual: the recipient receives activity events for unshared siblings in the owner's parent folder.

Impact

A single-file share recipient gains a real-time feed of file-activity metadata for the owner's parent folder — sibling names, operation types, and rename targets they were never granted access to. No file contents are exposed.

Remediation

For single-file shares, subscribe to the shared file's ID, or reject event subscriptions on the single-file share root view.
Store an authorization scope (navigator/share root) per subscriber and publish only events whose path stays within that scope.
Incorporate user/share scope into topic keys, not just file ID + client ID.
On subscriber reactivation, re-verify the requester still matches the subscriber and is authorized for the topic.

Severity

4.3 (Medium)


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

Show details on source website

JSON

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{
  "affected": [
    {
      "package": {
        "ecosystem": "Go",
        "name": "github.com/cloudreve/Cloudreve/v4"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "4.0.0-20260613030215-0b00dd308f13"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    },
    {
      "package": {
        "ecosystem": "Go",
        "name": "github.com/cloudreve/Cloudreve/v3"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "last_affected": "3.0.0-20250225100611-da4e44b77af4"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-55499"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-863"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-07-24T20:49:02Z",
    "nvd_published_at": null,
    "severity": "MODERATE"
  },
  "details": "## Summary\n \nWhen an authenticated recipient of a **single-file** share opens the file event stream (`GET /api/v4/file/events?uri=\u003cshare-root\u003e`), Cloudreve validates the URI by listing it and then subscribes the caller to `parent.ID()`. For a single-file share, the share navigator resolves the bare share-root URI to the **owner-side parent folder** of the shared file (not the file), while the visible listing is filtered down to just the shared file. The event hub then keys topics by numeric file ID only and, on each file change, fans the event out to subscribers of **every ancestor topic**, filtering only the client ID that caused the event \u2014 never the subscriber\u0027s share scope.\n \nConsequently, a recipient of one shared file can receive Server-Sent Events (type, sibling path/name, rename target, hashed file ID) for other files and subfolders in the owner\u0027s parent folder that were never shared. Contents are not disclosed; file-activity metadata is.\n\n### Details\n## Root cause (verified at `26b6b10`)\n \n**1. Events route \u2014 authenticated, feature-flagged, no share-scope check** (`routers/router.go`):\n```go\nfile := v4.Group(\"file\"); file.Use(middleware.RequiredScopes(types.ScopeFilesRead))\nfile.GET(\"events\",\n    middleware.LoginRequired(),\n    middleware.IsFunctionEnabled(func(c *gin.Context) bool { return dep.SettingProvider().EventHubEnabled(c) }),\n    controllers.FromQuery[explorer.ExplorerEventService](...), controllers.HandleExplorerEventsPush)\n```\n`EventHubEnabled` defaults `true` (`inventory/setting.go: \"fs_event_push_enabled\":\"1\"`).\n \n**2. Service subscribes to the listed parent\u0027s ID** (`service/explorer/events.go`):\n```go\nparent, _, err := m.List(c, uri, \u0026manager.ListArgs{Page:0, PageSize:1})   // also runs share validity/password\n...\nrx, resumed, err := eventHub.Subscribe(c, parent.ID(), requestInfo.ClientID)\n```\n \n**3. Single-file share `Root` swaps the share root to the owner parent** (`share_navigator.go`):\n```go\nn.shareRoot = newFile(nil, share.Edges.File)\n...\nif n.shareRoot.Type() == types.FileTypeFile {\n    n.singleFileShare = true\n    n.shareRoot = n.shareRoot.Parent   // \u003c-- owner-side parent folder\n}\n```\n \n**4. `To` returns that parent for the bare root URI** (`share_navigator.go`):\n```go\nelements := path.Elements()\nif len(elements) == 1 \u0026\u0026 n.singleFileShare { return latestSharedSingleFile(...) } // only when URI names the file\n...\nreturn current  // current == shareRoot == owner parent folder\n```\nThe bare root share URI has **zero** path elements (`URI.Elements()` returns nil for path `/`), so the `len(elements)==1` guard is skipped and `To` returns the parent folder. `dbfs.List` returns that as `parent`, so `parent.ID()` is the owner parent folder\u0027s real ID.\n \n**5. `Children` masks the broader parent** \u2014 for `singleFileShare` it returns only `[]*File{sharedFile}`, so the recipient\u0027s listing shows just the shared file even though the subscribed topic is the whole parent.\n \n**6. Publication fans out to ancestor topics with only a client-ID filter** (`dbfs/events.go`):\n```go\nfunc (f *DBFS) getEligibleSubscriber(ctx, file, checkParentPerm) []foundSubscriber {\n    roots := file.Ancestors()\n    for _, root := range roots {\n        subscribers := f.eventHub.GetSubscribers(ctx, root.Model.ID)\n        subscribers = lo.Filter(subscribers, func(s eventhub.Subscriber, _ int) bool {\n            return !(requestInfo != nil \u0026\u0026 s.ID() == requestInfo.ClientID)  // ONLY exclude the causing client\n        })\n        ...\n    }\n}\n// emit*: From: subscriber.relativePath(file)  // owner-side path of the changed sibling\n```\n`relativePath` trims the changed file\u0027s owner path by the subscribed root\u0027s owner path, yielding the sibling\u0027s name (e.g. `/Secret-Plan.pdf`). No check that the subscriber is authorized for the changed file or within their share scope.\n \n## Validation performed\n \nIndependent validation against commit `26b6b10` in a clean sandbox.\n \n**Source-verified (static):** all of (1)\u2013(6) confirmed verbatim, including the negative direction (an explicit `\u2026/shared.txt` URI resolves to the file, and `oss`/`qiniu`-style flows are irrelevant here).\n \n**Dynamic (control-flow executed):** the full binary is not buildable offline (modules behind an unreachable proxy, embedded frontend, DB/eventhub). The reseacher ran two harnesses:\n- A `net/url`-based check of the linchpin \u2014 the bare root share URI yields `0` path elements (so `To` returns the parent), while `\u2026/shared.txt` yields `1` (returns the file). This is the subtle point on which the whole finding turns, and it holds.\n- A model of `Root`/`To`/`getEligibleSubscriber`/`relativePath` driving the end-to-end flow:\n```\n[1] single-file share root URI -\u003e m.List parent = \"docs\" (id 10), NOT shared.txt (id 11)  -\u003e subscribed to owner parent\n[2] owner renames /docs/Secret-Plan.pdf -\u003e client \u0027attacker\u0027 receives: from=\"/Secret-Plan.pdf\" file_id=12 (topic 10)\n[3] CONTROL: event caused by attacker\u0027s own client id -\u003e suppressed (the only filter)\n[4] CONTROL: explicit URI \u0027shared.txt\u0027 -\u003e resolves to file (id 11) -\u003e no sibling events\n```\n\n## Steps to reproduce\n \n1. Owner shares a single file `shared.txt` from `/docs`, which also contains `Secret-Plan.pdf`.\n2. Recipient (logged-in, `Files.Read`, with the share password if any) opens the event stream on the share root:\n   ```\n   GET /api/v4/file/events?uri=cloudreve%3A%2F%2F\u003cshare-id\u003e%40share\n   Cookie: cloudreve-session=\u003crecipient-session\u003e\n   X-Cr-Client-Id: \u003cuuid\u003e\n   Accept: text/event-stream\n   ```\n3. Owner creates/renames/modifies/moves/deletes `Secret-Plan.pdf`.\n4. The recipient\u0027s stream receives, e.g.:\n   ```\n   event: event\n   data: {\"type\":\"rename\",\"file_id\":\"\u003chashed\u003e\",\"from\":\"/Secret-Plan.pdf\",\"to\":\"/Secret-Plan-v2.pdf\"}\n   ```\n \n**Expected:** the recipient only receives events for the shared file.\n**Actual:** the recipient receives activity events for unshared siblings in the owner\u0027s parent folder.\n \n## Impact\n \nA single-file share recipient gains a real-time feed of file-activity metadata for the owner\u0027s parent folder \u2014 sibling names, operation types, and rename targets they were never granted access to. No file contents are exposed.\n \n## Remediation\n \n- For single-file shares, subscribe to the shared file\u0027s ID, or reject event subscriptions on the single-file share root view.\n- Store an authorization scope (navigator/share root) per subscriber and publish only events whose path stays within that scope.\n- Incorporate user/share scope into topic keys, not just file ID + client ID.\n- On subscriber reactivation, re-verify the requester still matches the subscriber and is authorized for the topic.",
  "id": "GHSA-w8x7-h2px-xmq8",
  "modified": "2026-07-24T20:49:02Z",
  "published": "2026-07-24T20:49:02Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/cloudreve/cloudreve/security/advisories/GHSA-w8x7-h2px-xmq8"
    },
    {
      "type": "WEB",
      "url": "https://github.com/cloudreve/cloudreve/commit/0b00dd308f132d6e6e8476857ef79f4865600bbc"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/cloudreve/cloudreve"
    },
    {
      "type": "WEB",
      "url": "https://github.com/cloudreve/cloudreve/releases/tag/4.17.0"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Cloudreve: Broken Access Control in file event stream: a single-file share recipient is subscribed to the owner\u0027s parent folder and receives activity events for unshared siblings"
}

Sightings

Author	Source	Type	Date	Other

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

Detection rules are retrieved from Rulezet.

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.

Action not permitted

CVE-2026-55499 (GCVE-0-2026-55499)

GHSA-W8X7-H2PX-XMQ8

Summary

Details

Root cause (verified at 26b6b10)

Validation performed

Steps to reproduce

Impact

Remediation

Tags

Sightings

Nomenclature

Root cause (verified at `26b6b10`)