Critical severity · published Feb 25, 2026
CVE-2026-27607
RustFS's Missing Post Policy Validation leads to Arbitrary Object Write
9.1
CVSS
0.4%
EPSS
No
On KEV
Description
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.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Confidentiality
None
Integrity
High
Availability
High
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.4% · higher than 31% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
RU
rustfs · rustfs
>= 1.0.0-alpha.56, < 1.0.0-alpha.83 · source: vendor, NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-27607
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-27607
Vendor Advisory
https://github.com/rustfs/rustfs/security/advisories/GHSA-w5fh-f8xh-5x3p
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