CVE-2026-27607 | RustFS's Missing Post Policy Validation leads to Arbitrary Object Write

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.

Published: 2026-02-25 Last update: 2026-02-25 Assigner: [email protected] Source: [email protected]
NVD Status：Analyzed，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2026-27607 is rated Low Risk (38.3/100): CVSS High severity, with low exploitation likelihood (EPSS 0.05%). Monitor for updates and reassess as exploit intelligence or EPSS changes.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2026-27607

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-02-25 — 0.05% —

Full EPSS history (1 record total)

Common vulnerability scoring system (CVSS) metrics for CVE-2026-27607

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
8.1 3.1 HIGH
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:H Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:L)
A normal user session is enough; they don’t have to be admin.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:H)
They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 2.8 5.2 [email protected]
9.1 3.1 CRITICAL
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:H)
They could widely tamper with or forge data—trust in the data is badly hurt.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 3.9 5.2 [email protected]

Weakness enumeration for CVE-2026-27607

GitHub Security Advisory for CVE-2026-27607

GHSA-w5fh-f8xh-5x3p · Severity: high · Ecosystem: rust — RustFS: Missing Post Policy Validation leads to Arbitrary Object Write

Affected software / configurations for CVE-2026-27607

Vendor Product Version Raw CPE
rustfs rustfs 1.0.0 cpe:2.3:a:rustfs:rustfs:1.0.0:alpha56:*:*:*:rust:*:*
rustfs rustfs 1.0.0 cpe:2.3:a:rustfs:rustfs:1.0.0:alpha57:*:*:*:rust:*:*
rustfs rustfs 1.0.0 cpe:2.3:a:rustfs:rustfs:1.0.0:alpha58:*:*:*:rust:*:*
rustfs rustfs 1.0.0 cpe:2.3:a:rustfs:rustfs:1.0.0:alpha59:*:*:*:rust:*:*
rustfs rustfs 1.0.0 cpe:2.3:a:rustfs:rustfs:1.0.0:alpha60:*:*:*:rust:*:*
rustfs rustfs 1.0.0 cpe:2.3:a:rustfs:rustfs:1.0.0:alpha61:*:*:*:rust:*:*
rustfs rustfs 1.0.0 cpe:2.3:a:rustfs:rustfs:1.0.0:alpha62:*:*:*:rust:*:*
rustfs rustfs 1.0.0 cpe:2.3:a:rustfs:rustfs:1.0.0:alpha63:*:*:*:rust:*:*
rustfs rustfs 1.0.0 cpe:2.3:a:rustfs:rustfs:1.0.0:alpha64:*:*:*:rust:*:*
rustfs rustfs 1.0.0 cpe:2.3:a:rustfs:rustfs:1.0.0:alpha65:*:*:*:rust:*:*
rustfs rustfs 1.0.0 cpe:2.3:a:rustfs:rustfs:1.0.0:alpha66:*:*:*:rust:*:*
rustfs rustfs 1.0.0 cpe:2.3:a:rustfs:rustfs:1.0.0:alpha67:*:*:*:rust:*:*
rustfs rustfs 1.0.0 cpe:2.3:a:rustfs:rustfs:1.0.0:alpha68:*:*:*:rust:*:*
rustfs rustfs 1.0.0 cpe:2.3:a:rustfs:rustfs:1.0.0:alpha69:*:*:*:rust:*:*
rustfs rustfs 1.0.0 cpe:2.3:a:rustfs:rustfs:1.0.0:alpha70:*:*:*:rust:*:*
rustfs rustfs 1.0.0 cpe:2.3:a:rustfs:rustfs:1.0.0:alpha71:*:*:*:rust:*:*
rustfs rustfs 1.0.0 cpe:2.3:a:rustfs:rustfs:1.0.0:alpha72:*:*:*:rust:*:*
rustfs rustfs 1.0.0 cpe:2.3:a:rustfs:rustfs:1.0.0:alpha73:*:*:*:rust:*:*
rustfs rustfs 1.0.0 cpe:2.3:a:rustfs:rustfs:1.0.0:alpha74:*:*:*:rust:*:*
rustfs rustfs 1.0.0 cpe:2.3:a:rustfs:rustfs:1.0.0:alpha75:*:*:*:rust:*:*
rustfs rustfs 1.0.0 cpe:2.3:a:rustfs:rustfs:1.0.0:alpha76:*:*:*:rust:*:*
rustfs rustfs 1.0.0 cpe:2.3:a:rustfs:rustfs:1.0.0:alpha77:*:*:*:rust:*:*
rustfs rustfs 1.0.0 cpe:2.3:a:rustfs:rustfs:1.0.0:alpha78:*:*:*:rust:*:*
rustfs rustfs 1.0.0 cpe:2.3:a:rustfs:rustfs:1.0.0:alpha79:*:*:*:rust:*:*
rustfs rustfs 1.0.0 cpe:2.3:a:rustfs:rustfs:1.0.0:alpha80:*:*:*:rust:*:*
rustfs rustfs 1.0.0 cpe:2.3:a:rustfs:rustfs:1.0.0:alpha81:*:*:*:rust:*:*
rustfs rustfs 1.0.0 cpe:2.3:a:rustfs:rustfs:1.0.0:alpha82:*:*:*:rust:*:*

References for CVE-2026-27607

cvelogic Threat Intelligence