{"id":"GHSA-fc6g-2gcp-2qrq","summary":"RustFS has SourceIp bypass via spoofed X-Forwarded-For/Real-IP headers","details":"### Summary\nIP-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.\n\n### Details\n\n  - Vulnerable code: `rustfs/src/auth.rs:289-304` sets `remote_addr` from `X-Forwarded-For`/`X-Real-Ip`, then inserts `SourceIp` via\n    `get_source_ip_raw`, with no trust boundary or proxy validation:\n      - `let remote_addr = header.get(\"x-forwarded-for\").and_then(...).or_else(|| header.get(\"x-real-ip\")...).unwrap_or(\"127.0.0.1\");`\n      - `args.insert(\"SourceIp\", vec![get_source_ip_raw(header, remote_addr)]);`\n  - 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.\n  - No authentication is required beyond the request itself; the header is taken at face value even on direct connections.\n\n\n### PoC\n\n[rustfs-auth-trusted-ip-header-spoofing-poc.tar.gz](https://github.com/user-attachments/files/24038162/rustfs-auth-trusted-ip-header-spoofing-poc.tar.gz)\n\n\nSteps (already included in `rustfs-auth-trusted-ip-header-spoofing-poc/`):\n\n  1. Start RustFS with two local volumes, e.g.:\n\n```\n     mkdir -p /tmp/rustfs-data1 /tmp/rustfs-data2\n     RUSTFS_ACCESS_KEY=devadmin RUSTFS_SECRET_KEY=devadmin \\\n       cargo run --bin rustfs -- --address 0.0.0.0:9000 \\\n       /tmp/rustfs-data1 /tmp/rustfs-data2\n```\n\n  2. From `rustfs-auth-trusted-ip-header-spoofing-poc`/, run:\n\n```\n     ENDPOINT=http://127.0.0.1:9000 make run\n```\n\n     The script:\n      - Creates bucket `rustfs-trusted-ip-poc`.\n      - Applies a bucket policy allowing `s3:ListBucket` only from `10.0.0.5/32` (`Principal: {\"AWS\":[\"*\"]},` Resource array).\n      - Sends three unauthenticated `ListBucket` calls:\n          - Baseline (no spoof) → HTTP 403.\n          - Spoofed `X-Forwarded-For: 10.0.0.5` → HTTP 200 (policy bypass).\n          - Spoofed `X-Forwarded-For: 1.2.3.4` → HTTP 403.\n      - Responses saved to `poc-baseline.xml`, `poc-spoofed.xml`, `poc-deny.xml`.\n\n\n### Impact\n\n  - Vulnerability type: Authorization bypass of IP-allowlist (`aws:SourceIp`) via header spoofing.\n  - 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.\n\n### Credits\nIdentified by SecMate (https://secmate.dev) automated analysis and validated during manual triage.","aliases":["CVE-2026-21862"],"modified":"2026-02-03T19:03:44.212598Z","published":"2026-02-03T17:31:41Z","database_specific":{"cwe_ids":["CWE-290"],"severity":"HIGH","github_reviewed":true,"github_reviewed_at":"2026-02-03T17:31:41Z","nvd_published_at":"2026-02-03T16:16:12Z"},"references":[{"type":"WEB","url":"https://github.com/rustfs/rustfs/security/advisories/GHSA-fc6g-2gcp-2qrq"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-21862"},{"type":"WEB","url":"https://github.com/rustfs/rustfs/commit/b4ba62fa3300b5b258fdc0da141481e3be7ea960"},{"type":"PACKAGE","url":"https://github.com/rustfs/rustfs"}],"affected":[{"package":{"name":"rustfs","ecosystem":"crates.io","purl":"pkg:cargo/rustfs"},"ranges":[{"type":"SEMVER","events":[{"introduced":"0"},{"fixed":"1.0.0-alpha.78"}]}],"database_specific":{"source":"https://github.com/github/advisory-database/blob/main/advisories/github-reviewed/2026/02/GHSA-fc6g-2gcp-2qrq/GHSA-fc6g-2gcp-2qrq.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V4","score":"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"}]}