RustFS has IAM deny_only Short-Circuit that Allows Privilege Escalation via Service Account Minting

published 2026-01-08 10 mo ago modified 2026-06-17 4 mo ago also GHSA-xgr5-qc6w-vcg9 , EUVD-2026-1471

cvss: 9.8; version 3.1, NVD
cisa kev: Not listed; not in CISA's catalog
epss: 0.4%; EPSS 0.4% chance of exploitation in 30 days, percentile 36%
public exploits: 0; none known

RustFS is a distributed object storage system built in Rust. In versions 1.0.0-alpha.13 through 1.0.0-alpha.78, a flawed `deny_only` short-circuit in RustFS IAM allows a restricted service account or STS credential to self-issue an unrestricted service account, inheriting the parent’s full privileges. This enables privilege escalation and bypass of session/inline policy restrictions. Version 1.0.0-alpha.79 fixes the issue.

Patch / fix

fixed in 1

crates.io rustfs 1.0.0-alpha.79

CISA SSVC

Exploitation: Proof of concept is public
Automatable: no
Technical impact: partial
Assessed: 10 mo ago (2026-01-08)

Exploit prediction

0.42% chance of exploitation in the next 30 days, higher than 36% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

github.com https://github.com/rustfs/rustfs/security/advisories/GHSA-xgr5-qc6w-vcg9 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by	version	score	vector
CNA	4.0	5.7	CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N/E:P
CNA	4.0	5.7	CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N/E:P/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
NVD	3.1	9.8	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Affected packages

ecosystem	package	affected	fixed in
crates.io	rustfs	>=1.0.0-alpha.13, <1.0.0-alpha.79	1.0.0-alpha.79

Affected products

rustfs rustfs

Classification

Weakness

CWE-269 Improper Privilege Management
CWE-284 Improper Access Control
CWE-522 Insufficiently Protected Credentials

References

github.com /rustfs/rustfs/security/advisories/GHSA-xgr5-qc6w-vcg9
exploit, web, vendor-advisory
nvd.nist.gov /vuln/detail/CVE-2026-22043
advisory
github.com /rustfs/rustfs
package

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

Summary