{"id":"EUVD-2026-28822","revision":null,"records":[{"revision":"1234bc11637446979a69d107caac3bd0","observedAt":"2026-10-23T15:48:27.903+00:00","statement":{"source":"cve-program","id":"CVE-2026-42189","aliases":[],"title":"Russh: Pre-auth DoS via unbounded allocation in keyboard-interactive auth","description":"Russh is a Rust SSH client & server library. Prior to version 0.60.1, a pre-authentication denial-of-service vulnerability exists in the server's keyboard-interactive authentication handler. A malicious client can crash any russh-based server that implements keyboard-interactive auth (e.g., for 2FA/TOTP) with a single malformed packet, requiring no credentials. This issue has been patched in version 0.60.1.","state":0,"publishedAt":"2026-05-08T19:49:51.179+00:00","modifiedAt":"2026-05-11T14:23:49.308+00:00","affected":[{"ecosystem":"Vendor product","name":"russh","ranges":[],"versions":[],"rawVersionEvidence":"{\n                    \"vendor\": \"Eugeny\",\n                    \"product\": \"russh\",\n                    \"versions\": [\n                        {\n                            \"version\": \"< 0.60.1\",\n                            \"status\": \"affected\"\n                        }\n                    ]\n                }"}],"metrics":[{"system":"CVSS 3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","score":7.5,"severity":"HIGH"}],"references":["https://github.com/Eugeny/russh/security/advisories/GHSA-f5v4-2wr6-hqmg","https://github.com/Eugeny/russh/commit/6c3c80a9b6d60763d6227d60fa8310e57172a4d1","https://github.com/Eugeny/russh/releases/tag/v0.60.1"],"sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-42189","license":"CVE Program Terms of Use","key":"cve-program:CVE-2026-42189","identifiers":["CVE-2026-42189"]},"retained":false,"historicalAffected":[]},{"revision":"457d383cade043308e8c9f99482c0f50","observedAt":"2026-11-07T09:32:22.07+00:00","statement":{"source":"euvd","id":"EUVD-2026-28822","aliases":["CVE-2026-42189"],"title":"Russh is a Rust SSH client & server library. 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This issue has been patched in version 0.60.1.","state":0,"publishedAt":null,"modifiedAt":null,"affected":[],"metrics":[{"system":"EUVD CVSS 3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","score":7.5,"severity":null}],"references":["https://github.com/Eugeny/russh/security/advisories/GHSA-f5v4-2wr6-hqmg","https://github.com/Eugeny/russh/commit/6c3c80a9b6d60763d6227d60fa8310e57172a4d1","https://github.com/Eugeny/russh/releases/tag/v0.60.1"],"sourceUrl":"https://euvd.enisa.europa.eu/vulnerability/EUVD-2026-28822","license":"ENISA EUVD · source terms and attribution apply","enrichment":{"sourceStatus":null,"weaknesses":[],"productCriteria":[],"sourceDates":{"datePublished":"May 8, 2026, 7:49:51 PM","dateUpdated":"May 11, 2026, 2:23:49 PM"},"relatedAdvisories":[],"note":"EUVD source date text has no stated timezone and is retained without inventing a UTC instant. Related bulletin membership is not an alias, common cause or applicability claim. A missing vector with a zero score is treated as unrated. Complete vendor/product and underlying source evidence remains in the original JSON."},"key":"euvd:EUVD-2026-28822","identifiers":["EUVD-2026-28822","CVE-2026-42189"]},"retained":false,"historicalAffected":[]},{"revision":"ee363e4a66ed478fb7c561db341ee057","observedAt":"2026-10-27T11:12:01.124+00:00","statement":{"source":"nvd","id":"CVE-2026-42189","aliases":[],"title":"Russh is a Rust SSH client & server library. Prior to version 0.60.1, a pre-authentication denial-of-service vulnerability exists in the server's keyboard-interactive authentication handler. A malicious client can crash any russh-based serv…","description":"Russh is a Rust SSH client & server library. Prior to version 0.60.1, a pre-authentication denial-of-service vulnerability exists in the server's keyboard-interactive authentication handler. A malicious client can crash any russh-based server that implements keyboard-interactive auth (e.g., for 2FA/TOTP) with a single malformed packet, requiring no credentials. This issue has been patched in version 0.60.1.","state":0,"publishedAt":"2026-05-08T20:16:31.443+00:00","modifiedAt":"2026-10-26T18:10:00.173+00:00","affected":[],"metrics":[{"system":"CVSS 3.1 · security-advisories@github.com · Secondary","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","score":7.5,"severity":"HIGH"}],"references":["https://github.com/Eugeny/russh/commit/6c3c80a9b6d60763d6227d60fa8310e57172a4d1","https://github.com/Eugeny/russh/releases/tag/v0.60.1","https://github.com/Eugeny/russh/security/advisories/GHSA-f5v4-2wr6-hqmg"],"sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-42189","license":"NIST NVD usage terms; underlying source attribution retained","enrichment":{"sourceStatus":"Analyzed","weaknesses":["CWE-770","CWE-789"],"productCriteria":["cpe:2.3:a:russh_project:russh:*:*:*:*:*:rust:*:*","cpe:2.3:a:warpgate_project:warpgate:*:*:*:*:*:*:*:*"],"sourceDates":{"published":"2026-05-08T20:16:31.443","lastModified":"2026-10-26T18:10:00.173"},"relatedAdvisories":[],"note":"NVD analysis and CPE criteria are source context, not proof that a package or your environment is affected. Complete affected data, logical configurations and SSVC are retained in the original JSON."},"key":"nvd:CVE-2026-42189","identifiers":["CVE-2026-42189"]},"retained":false,"historicalAffected":[]},{"revision":"65e4576db2ac4c9ea898811d64afa131","observedAt":"2026-10-24T13:19:54.901+00:00","statement":{"source":"osv","id":"GHSA-f5v4-2wr6-hqmg","aliases":["CVE-2026-42189"],"title":"russh has pre-auth DoS via unbounded allocation in its keyboard-interactive auth handler","description":"## Summary\n\nA pre-authentication denial-of-service vulnerability exists in the server's keyboard-interactive authentication handler. A malicious client can crash any russh-based server that implements keyboard-interactive auth (e.g., for 2FA/TOTP) with a single malformed packet, requiring no credentials.\n\n## Vulnerability Details\n\nIn `russh/src/server/encrypted.rs`, the function `read_userauth_info_response` decodes a `u32` count from the client's `SSH_MSG_USERAUTH_INFO_RESPONSE` and passes it directly to `Vec::with_capacity()`:\n\n```rust\nlet n = map_err!(u32::decode(r))?;\n\n// Bound both allocation and iteration by remaining packet data to\n// prevent a malicious client from causing a multi-GB allocation or\n// billions of loop iterations with a crafted count.\n// Each response needs at least 4 bytes (length prefix).\nlet max_responses = r.remaining_len().saturating_add(3) / 4;\nlet n = (n as usize).min(max_responses);\nlet mut responses = Vec::with_capacity(n);\nfor _ in 0..n {\n    responses.push(Bytes::decode(r).ok())\n}\n```\n\nAn attacker can send `n = 0x10000000` (268M) or larger in a minimal packet (~50 bytes after encryption). The server attempts to allocate `n * ~24 bytes` (size of `Option<Bytes>`) = ~6.4GB, causing an OOM crash.\n\n## Attack Flow\n\n1. Attacker connects via TCP, completes key exchange (no credentials needed -- this is the anonymous DH handshake, not authentication)\n2. Sends `USERAUTH_REQUEST` with method `keyboard-interactive`\n3. Server handler returns `Auth::Partial` with prompts (standard for 2FA/TOTP)\n4. Attacker sends `USERAUTH_INFO_RESPONSE` with `n = 0x10000000` and no response data\n5. Server calls `Vec::with_capacity(268_435_456)`, OOM killed\n\nNo authentication is required. The allocation occurs before the handler validates any credentials. The attack is repeatable faster than the server can restart.\n\n## Affected Configurations\n\nAny russh-based server where the `Handler::auth_keyboard_interactive` implementation returns `Auth::Partial` (i.e., sends prompts to the client). The default handler returns `Auth::reject()` and is not affected.\n\nSource code review suggests that downstream projects using keyboard-interactive for multi-step auth (e.g., TOTP/2FA) follow the affected pattern, since returning `Auth::Partial` before credential verification is the intended API usage for prompting.\n\n## Confirmed End-to-End PoC\n\nThere is a complete Docker-contained PoC confirming the OOM kill:\n- Minimal russh server returning `Auth::Partial` for keyboard-interactive\n- Python client (paramiko for key exchange) sends malformed `USERAUTH_INFO_RESPONSE`\n- Container with 512MB memory limit; server is OOM-killed (exit code 137)\n\nAvailable on request.\n\n## Proposed Fix\n\nCap the `Vec::with_capacity` allocation to what the remaining packet data can actually contain. Each response requires at least 4 bytes (length prefix), so:\n\n```rust\nlet n = map_err!(u32::decode(r))?;\n\n// Bound both allocation and iteration by remaining packet data to\n// prevent a malicious client from causing a multi-GB allocation or\n// billions of loop iterations with a crafted count.\n// Each response needs at least 4 bytes (length prefix).\nlet max_responses = r.remaining_len().saturating_add(3) / 4;\nlet n = (n as usize).min(max_responses);\nlet mut responses = Vec::with_capacity(n);\nfor _ in 0..n {\n    responses.push(Bytes::decode(r).ok())\n}\n```\n\nThis bounds the allocation to at most the packet size (~256KB), while preserving the existing behavior for well-formed packets. This fix has been implemented, tested, and contributed via the temporary private fork.\n\n## Severity\n\nPre-auth, remote, no credentials required, crashes the server process affecting all active sessions.","state":0,"publishedAt":"2026-04-24T15:39:37+00:00","modifiedAt":"2026-09-10T03:51:01.5947155+00:00","affected":[{"ecosystem":"crates.io","name":"russh","ranges":[{"type":"SEMVER","events":[{"kind":"introduced","version":"0"},{"kind":"fixed","version":"0.60.1"}]}],"versions":[],"rawVersionEvidence":null}],"metrics":[{"system":"CVSS_V3","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","score":null,"severity":null},{"system":"Publisher rating","vector":null,"score":null,"severity":"HIGH"}],"references":["https://github.com/Eugeny/russh/security/advisories/GHSA-f5v4-2wr6-hqmg","https://nvd.nist.gov/vuln/detail/CVE-2026-42189","https://github.com/Eugeny/russh/commit/6c3c80a9b6d60763d6227d60fa8310e57172a4d1","https://github.com/Eugeny/russh","https://github.com/Eugeny/russh/releases/tag/v0.60.1"],"sourceUrl":"https://github.com/advisories/GHSA-f5v4-2wr6-hqmg","license":"GitHub Advisory Database · CC-BY-4.0","key":"osv:GHSA-f5v4-2wr6-hqmg","identifiers":["GHSA-f5v4-2wr6-hqmg","CVE-2026-42189"]},"retained":false,"historicalAffected":[]}],"coverage":[{"source":"cisa-kev:global","scope":"Complete CISA KEV catalog; all vendors. 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