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RustFS has SourceIp bypass via spoofed X-Forwarded-For/Real-IP headers

High severity GitHub Reviewed Published Feb 3, 2026 in rustfs/rustfs • Updated Feb 3, 2026

Package

cargo rustfs (Rust)

Affected versions

< 1.0.0-alpha.78

Patched versions

1.0.0-alpha.78

Description

Summary

IP-based access control can be bypassed: get_condition_values trusts client-supplied X-Forwarded-For/X-Real-Ip without verifying a trusted proxy, so any reachable client can spoof aws:SourceIp and satisfy IP-allowlist policies.

Details

  • Vulnerable code: rustfs/src/auth.rs:289-304 sets remote_addr from X-Forwarded-For/X-Real-Ip, then inserts SourceIp via
    get_source_ip_raw, with no trust boundary or proxy validation:
    • let remote_addr = header.get("x-forwarded-for").and_then(...).or_else(|| header.get("x-real-ip")...).unwrap_or("127.0.0.1");
    • args.insert("SourceIp", vec![get_source_ip_raw(header, remote_addr)]);
  • This value feeds IAM/bucket policy evaluation in rustfs/src/storage/access.rs (authorization path), so any request that forges the header can meet aws:SourceIp conditions.
  • No authentication is required beyond the request itself; the header is taken at face value even on direct connections.

PoC

rustfs-auth-trusted-ip-header-spoofing-poc.tar.gz

Steps (already included in rustfs-auth-trusted-ip-header-spoofing-poc/):

  1. Start RustFS with two local volumes, e.g.:
     mkdir -p /tmp/rustfs-data1 /tmp/rustfs-data2
     RUSTFS_ACCESS_KEY=devadmin RUSTFS_SECRET_KEY=devadmin \
       cargo run --bin rustfs -- --address 0.0.0.0:9000 \
       /tmp/rustfs-data1 /tmp/rustfs-data2
  1. From rustfs-auth-trusted-ip-header-spoofing-poc/, run:
     ENDPOINT=http://127.0.0.1:9000 make run

 The script:
  - Creates bucket `rustfs-trusted-ip-poc`.
  - Applies a bucket policy allowing `s3:ListBucket` only from `10.0.0.5/32` (`Principal: {"AWS":["*"]},` Resource array).
  - Sends three unauthenticated `ListBucket` calls:
      - Baseline (no spoof) → HTTP 403.
      - Spoofed `X-Forwarded-For: 10.0.0.5` → HTTP 200 (policy bypass).
      - Spoofed `X-Forwarded-For: 1.2.3.4` → HTTP 403.
  - Responses saved to `poc-baseline.xml`, `poc-spoofed.xml`, `poc-deny.xml`.

Impact

  • Vulnerability type: Authorization bypass of IP-allowlist (aws:SourceIp) via header spoofing.
  • Who is impacted: Any deployment relying on aws:SourceIp in IAM/bucket policies for S3 operations. Attackers with network reach to RustFS can forge forwarded-IP headers to gain list/read/write where IP restrictions were meant to block them.

Credits

Identified by SecMate (https://secmate.dev) automated analysis and validated during manual triage.

References

@loverustfs loverustfs published to rustfs/rustfs Feb 3, 2026
Published by the National Vulnerability Database Feb 3, 2026
Published to the GitHub Advisory Database Feb 3, 2026
Reviewed Feb 3, 2026
Last updated Feb 3, 2026

Severity

High

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v4 base metrics

Exploitability Metrics
Attack Vector Network
Attack Complexity Low
Attack Requirements None
Privileges Required None
User interaction None
Vulnerable System Impact Metrics
Confidentiality None
Integrity High
Availability None
Subsequent System Impact Metrics
Confidentiality None
Integrity None
Availability None

CVSS v4 base metrics

Exploitability Metrics
Attack Vector: This metric reflects the context by which vulnerability exploitation is possible. This metric value (and consequently the resulting severity) will be larger the more remote (logically, and physically) an attacker can be in order to exploit the vulnerable system. The assumption is that the number of potential attackers for a vulnerability that could be exploited from across a network is larger than the number of potential attackers that could exploit a vulnerability requiring physical access to a device, and therefore warrants a greater severity.
Attack Complexity: This metric captures measurable actions that must be taken by the attacker to actively evade or circumvent existing built-in security-enhancing conditions in order to obtain a working exploit. These are conditions whose primary purpose is to increase security and/or increase exploit engineering complexity. A vulnerability exploitable without a target-specific variable has a lower complexity than a vulnerability that would require non-trivial customization. This metric is meant to capture security mechanisms utilized by the vulnerable system.
Attack Requirements: This metric captures the prerequisite deployment and execution conditions or variables of the vulnerable system that enable the attack. These differ from security-enhancing techniques/technologies (ref Attack Complexity) as the primary purpose of these conditions is not to explicitly mitigate attacks, but rather, emerge naturally as a consequence of the deployment and execution of the vulnerable system.
Privileges Required: This metric describes the level of privileges an attacker must possess prior to successfully exploiting the vulnerability. The method by which the attacker obtains privileged credentials prior to the attack (e.g., free trial accounts), is outside the scope of this metric. Generally, self-service provisioned accounts do not constitute a privilege requirement if the attacker can grant themselves privileges as part of the attack.
User interaction: This metric captures the requirement for a human user, other than the attacker, to participate in the successful compromise of the vulnerable system. This metric determines whether the vulnerability can be exploited solely at the will of the attacker, or whether a separate user (or user-initiated process) must participate in some manner.
Vulnerable System Impact Metrics
Confidentiality: This metric measures the impact to the confidentiality of the information managed by the VULNERABLE SYSTEM due to a successfully exploited vulnerability. Confidentiality refers to limiting information access and disclosure to only authorized users, as well as preventing access by, or disclosure to, unauthorized ones.
Integrity: This metric measures the impact to integrity of a successfully exploited vulnerability. Integrity refers to the trustworthiness and veracity of information. Integrity of the VULNERABLE SYSTEM is impacted when an attacker makes unauthorized modification of system data. Integrity is also impacted when a system user can repudiate critical actions taken in the context of the system (e.g. due to insufficient logging).
Availability: This metric measures the impact to the availability of the VULNERABLE SYSTEM resulting from a successfully exploited vulnerability. While the Confidentiality and Integrity impact metrics apply to the loss of confidentiality or integrity of data (e.g., information, files) used by the system, this metric refers to the loss of availability of the impacted system itself, such as a networked service (e.g., web, database, email). Since availability refers to the accessibility of information resources, attacks that consume network bandwidth, processor cycles, or disk space all impact the availability of a system.
Subsequent System Impact Metrics
Confidentiality: This metric measures the impact to the confidentiality of the information managed by the SUBSEQUENT SYSTEM due to a successfully exploited vulnerability. Confidentiality refers to limiting information access and disclosure to only authorized users, as well as preventing access by, or disclosure to, unauthorized ones.
Integrity: This metric measures the impact to integrity of a successfully exploited vulnerability. Integrity refers to the trustworthiness and veracity of information. Integrity of the SUBSEQUENT SYSTEM is impacted when an attacker makes unauthorized modification of system data. Integrity is also impacted when a system user can repudiate critical actions taken in the context of the system (e.g. due to insufficient logging).
Availability: This metric measures the impact to the availability of the SUBSEQUENT SYSTEM resulting from a successfully exploited vulnerability. While the Confidentiality and Integrity impact metrics apply to the loss of confidentiality or integrity of data (e.g., information, files) used by the system, this metric refers to the loss of availability of the impacted system itself, such as a networked service (e.g., web, database, email). Since availability refers to the accessibility of information resources, attacks that consume network bandwidth, processor cycles, or disk space all impact the availability of a system.
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N/E:P

EPSS score

Exploit Prediction Scoring System (EPSS)

This score estimates the probability of this vulnerability being exploited within the next 30 days. Data provided by FIRST.
(12th percentile)

Weaknesses

Authentication Bypass by Spoofing

This attack-focused weakness is caused by incorrectly implemented authentication schemes that are subject to spoofing attacks. Learn more on MITRE.

CVE ID

CVE-2026-21862

GHSA ID

GHSA-fc6g-2gcp-2qrq

Source code

Credits

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