Vulnerability-Lookup

CVE-2026-27607 (GCVE-0-2026-27607)

Vulnerability from cvelistv5 – Published: 2026-02-25 02:10 – Updated: 2026-02-25 20:06

Title

RustFS's Missing Post Policy Validation leads to Arbitrary Object Write

Summary

RustFS is a distributed object storage system built in Rust. In versions 1.0.0-alpha.56 through 1.0.0-alpha.82, RustFS does not validate policy conditions in presigned POST uploads (PostObject), allowing attackers to bypass content-length-range, starts-with, and Content-Type constraints. This enables unauthorized file uploads exceeding size limits, uploads to arbitrary object keys, and content-type spoofing, potentially leading to storage exhaustion, unauthorized data access, and security bypasses. Version 1.0.0-alpha.83 fixes the issue.

Severity ?

8.1 (High)


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

CWE

CWE-20 - Improper Input Validation
CWE-863 - Incorrect Authorization

Assigner

GitHub_M

References

URL

Tags

https://github.com/rustfs/rustfs/security/advisor…

x_refsource_CONFIRM

Impacted products

	Vendor	Product	Version
	rustfs	rustfs	Affected: >= 1.0.0-alpha.56, < 1.0.0-alpha.83

Show details on NVD website

JSON

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GHSA-W5FH-F8XH-5X3P

Vulnerability from github – Published: 2026-02-25 22:38 – Updated: 2026-02-25 22:38

Summary

RustFS: Missing Post Policy Validation leads to Arbitrary Object Write

Details

Summary

RustFS does not validate policy conditions in presigned POST uploads (PostObject), allowing attackers to bypass content-length-range, starts-with, and Content-Type constraints. This enables unauthorized file uploads exceeding size limits, uploads to arbitrary object keys, and content-type spoofing, potentially leading to storage exhaustion, unauthorized data access, and security bypasses.

Details

When generating presigned POST URLs via the AWS SDK, applications can specify policy conditions to restrict uploads. RustFS accepts these presigned requests but fails to validate the following conditions server-side:

content-length-range not enforced: The server does not verify that the uploaded file size falls within the specified minimum and maximum bounds. An attacker can upload arbitrarily large files despite restrictions.
starts-with not enforced: The server does not validate that the object key matches the required prefix. An attacker can modify the key field to upload files to any path in the bucket.
Content-Type (exact match) not enforced: The server does not verify that the uploaded file's content type matches the policy constraint. An attacker can upload files with any content type.

The vulnerability exists in the PostObject endpoint implementation, where the signed policy conditions are not parsed and validated against the actual upload request.

Impact

Vulnerability Type: Improper Input Validation / Authorization Bypass

Who is affected:

Any application using RustFS as an S3-compatible backend that relies on presigned POST policy conditions for access control or upload restrictions.

Potential attack scenarios:

Storage Exhaustion / Denial of Service: Attackers can upload arbitrarily large files, bypassing size limits, potentially filling up disk space and causing service outages.
Unauthorized Data Access/Modification: By bypassing starts-with conditions, attackers can upload files to restricted paths (e.g., overwriting configuration files, accessing other users' directories in multi-tenant systems).
Content-Type Spoofing: Bypassing content-type restrictions could enable serving malicious content (e.g., HTML/JavaScript files in contexts expecting only images), potentially leading to XSS attacks if files are served to browsers.

Severity: The vulnerability allows complete bypass of server-enforced upload policies, undermining the security model that applications rely upon.

Severity ?

8.1 (High)


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

Show details on source website

JSON

To clipboard

{
  "affected": [
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c 1.0.0-alpha.82"
      },
      "package": {
        "ecosystem": "crates.io",
        "name": "rustfs"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "1.0.0-alpha.56"
            },
            {
              "fixed": "1.0.0-alpha.83"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-27607"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-863"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-02-25T22:38:40Z",
    "nvd_published_at": "2026-02-25T03:16:04Z",
    "severity": "HIGH"
  },
  "details": "### Summary\nRustFS does not validate policy conditions in presigned POST uploads (PostObject), allowing attackers to bypass content-length-range, starts-with, and Content-Type constraints. This enables unauthorized file uploads exceeding size limits, uploads to arbitrary object keys, and content-type spoofing, potentially leading to storage exhaustion, unauthorized data access, and security bypasses.\n\n### Details\nWhen generating presigned POST URLs via the AWS SDK, applications can specify policy conditions to restrict uploads. RustFS accepts these presigned requests but fails to validate the following conditions server-side:\n\n1. `content-length-range` not enforced: The server does not verify that the uploaded file size falls within the specified minimum and maximum bounds. An attacker can upload arbitrarily large files despite restrictions.\n2. `starts-with` not enforced: The server does not validate that the object key matches the required prefix. An attacker can modify the key field to upload files to any path in the bucket.\n3. `Content-Type` (exact match) not enforced: The server does not verify that the uploaded file\u0027s content type matches the policy constraint. An attacker can upload files with any content type.\n\nThe vulnerability exists in the PostObject endpoint implementation, where the signed policy conditions are not parsed and validated against the actual upload request.\n\n### Impact\nVulnerability Type: Improper Input Validation / Authorization Bypass\n##### Who is affected:\nAny application using RustFS as an S3-compatible backend that relies on presigned POST policy conditions for access control or upload restrictions.\n##### Potential attack scenarios:\n1. Storage Exhaustion / Denial of Service: Attackers can upload arbitrarily large files, bypassing size limits, potentially filling up disk space and causing service outages.\n2. Unauthorized Data Access/Modification: By bypassing starts-with conditions, attackers can upload files to restricted paths (e.g., overwriting configuration files, accessing other users\u0027 directories in multi-tenant systems).\n3. Content-Type Spoofing: Bypassing content-type restrictions could enable serving malicious content (e.g., HTML/JavaScript files in contexts expecting only images), potentially leading to XSS attacks if files are served to browsers.\n\n**Severity**:  The vulnerability allows complete bypass of server-enforced upload policies, undermining the security model that applications rely upon.",
  "id": "GHSA-w5fh-f8xh-5x3p",
  "modified": "2026-02-25T22:38:40Z",
  "published": "2026-02-25T22:38:40Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/rustfs/rustfs/security/advisories/GHSA-w5fh-f8xh-5x3p"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-27607"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/rustfs/rustfs"
    },
    {
      "type": "WEB",
      "url": "https://github.com/rustfs/rustfs/releases/tag/1.0.0-alpha.83"
    }
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  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:H",
      "type": "CVSS_V3"
    }
  ],
  "summary": "RustFS: Missing Post Policy Validation leads to Arbitrary Object Write"
}

FKIE_CVE-2026-27607

Vulnerability from fkie_nvd - Published: 2026-02-25 03:16 - Updated: 2026-02-25 15:37

Severity ?

8.1 (High) - CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:H
9.1 (Critical) - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H

Summary

References

	URL	Tags
	security-advisories@github.com	https://github.com/rustfs/rustfs/security/advisories/GHSA-w5fh-f8xh-5x3p	Vendor Advisory

Impacted products

Vendor	Product	Version
rustfs	rustfs	1.0.0
rustfs	rustfs	1.0.0
rustfs	rustfs	1.0.0
rustfs	rustfs	1.0.0
rustfs	rustfs	1.0.0
rustfs	rustfs	1.0.0
rustfs	rustfs	1.0.0
rustfs	rustfs	1.0.0
rustfs	rustfs	1.0.0
rustfs	rustfs	1.0.0
rustfs	rustfs	1.0.0
rustfs	rustfs	1.0.0
rustfs	rustfs	1.0.0
rustfs	rustfs	1.0.0
rustfs	rustfs	1.0.0
rustfs	rustfs	1.0.0
rustfs	rustfs	1.0.0
rustfs	rustfs	1.0.0
rustfs	rustfs	1.0.0
rustfs	rustfs	1.0.0
rustfs	rustfs	1.0.0
rustfs	rustfs	1.0.0
rustfs	rustfs	1.0.0
rustfs	rustfs	1.0.0
rustfs	rustfs	1.0.0
rustfs	rustfs	1.0.0
rustfs	rustfs	1.0.0

JSON

To clipboard

{
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  "cveTags": [],
  "descriptions": [
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      "lang": "en",
      "value": "RustFS is a distributed object storage system built in Rust. In versions 1.0.0-alpha.56 through 1.0.0-alpha.82, RustFS does not validate policy conditions in presigned POST uploads (PostObject), allowing attackers to bypass content-length-range, starts-with, and Content-Type constraints. This enables unauthorized file uploads exceeding size limits, uploads to arbitrary object keys, and content-type spoofing, potentially leading to storage exhaustion, unauthorized data access, and security bypasses. Version 1.0.0-alpha.83 fixes the issue."
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}

Sightings

Author	Source	Type	Date

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.

Action not permitted

CVE-2026-27607 (GCVE-0-2026-27607)

GHSA-W5FH-F8XH-5X3P

Summary

Details

Impact

Who is affected:

Potential attack scenarios:

FKIE_CVE-2026-27607

Tags

Sightings

Nomenclature