{"id":"CVE-2026-102823","revision":null,"records":[{"revision":"941fbd7f7185404f9b1a5cbdcd9e4b17","observedAt":"2026-10-23T15:48:27.903+00:00","statement":{"source":"cve-program","id":"CVE-2026-102823","aliases":[],"title":"russh: Client-side channel-scoped Handler callbacks fire for channel IDs the client never opened","description":"Russh is a Rust SSH client and server library. Prior to 0.63.1, client_read_authenticated in russh/src/client/encrypted.rs forwards CHANNEL_DATA, CHANNEL_EXTENDED_DATA, CHANNEL_EOF, CHANNEL_CLOSE, CHANNEL_OPEN_FAILURE, CHANNEL_SUCCESS, CHANNEL_FAILURE, and CHANNEL_REQUEST subtypes exit-status, exit-signal, and xon-xoff to public client::Handler callbacks without confirming that the ChannelId belongs to a channel the client opened and established. A malicious SSH server can send lifecycle events for predicted, unopened, unconfirmed, or released channel identifiers, causing application panics or corrupting command completion and exit-code tracking. This issue is fixed in version 0.63.1.","state":0,"publishedAt":"2026-09-29T18:25:58.084+00:00","modifiedAt":"2026-10-02T12:20:10.605+00:00","affected":[{"ecosystem":"Vendor product","name":"russh","ranges":[],"versions":[],"rawVersionEvidence":"{\n                    \"vendor\": \"Eugeny\",\n                    \"product\": \"russh\",\n                    \"versions\": [\n                        {\n                            \"version\": \"< 0.63.1\",\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:H/A:N","score":7.5,"severity":"HIGH"}],"references":["https://github.com/Eugeny/russh/security/advisories/GHSA-47hw-gvq5-r2gm","https://github.com/Eugeny/russh/commit/3430fd26ecafc0dc3705210f5f39a9119fa22774","https://github.com/Eugeny/russh/releases/tag/v0.63.1"],"sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-102823","license":"CVE Program Terms of Use","key":"cve-program:CVE-2026-102823","identifiers":["CVE-2026-102823"]},"retained":false,"historicalAffected":[]},{"revision":"75bf8cabcda04205ba73429019e9065f","observedAt":"2026-11-11T05:29:28.92+00:00","statement":{"source":"euvd","id":"EUVD-2026-89206","aliases":["CVE-2026-102823","GHSA-47hw-gvq5-r2gm"],"title":"Russh is a Rust SSH client and server library. Prior to 0.63.1, client_read_authenticated in russh/src/client/encrypted.rs forwards CHANNEL_DATA, CHANNEL_EXTENDED_DATA, CHANNEL_EOF, CHANNEL_CLOSE, CHANNEL_OPEN_FAILURE, CHANNEL_SUCCESS, CHAN…","description":"Russh is a Rust SSH client and server library. Prior to 0.63.1, client_read_authenticated in russh/src/client/encrypted.rs forwards CHANNEL_DATA, CHANNEL_EXTENDED_DATA, CHANNEL_EOF, CHANNEL_CLOSE, CHANNEL_OPEN_FAILURE, CHANNEL_SUCCESS, CHANNEL_FAILURE, and CHANNEL_REQUEST subtypes exit-status, exit-signal, and xon-xoff to public client::Handler callbacks without confirming that the ChannelId belongs to a channel the client opened and established. A malicious SSH server can send lifecycle events for predicted, unopened, unconfirmed, or released channel identifiers, causing application panics or corrupting command completion and exit-code tracking. This issue is fixed in version 0.63.1.","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:H/A:N","score":7.5,"severity":null}],"references":["https://github.com/Eugeny/russh/security/advisories/GHSA-47hw-gvq5-r2gm","https://github.com/Eugeny/russh/commit/3430fd26ecafc0dc3705210f5f39a9119fa22774","https://github.com/Eugeny/russh/releases/tag/v0.63.1"],"sourceUrl":"https://euvd.enisa.europa.eu/vulnerability/EUVD-2026-89206","license":"ENISA EUVD · source terms and attribution apply","enrichment":{"sourceStatus":null,"weaknesses":[],"productCriteria":[],"sourceDates":{"datePublished":"Sep 29, 2026, 6:25:58 PM","dateUpdated":"Oct 2, 2026, 12:20:10 PM"},"relatedAdvisories":[{"id":"RHSA-2026:74586","title":"Red Hat Security Advisory: Red Hat Hardened Images RPMs Security Update","vulnerabilityIds":["CVE-2026-102821","CVE-2026-102823","CVE-2026-102824","CVE-2026-102825"]}],"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-2026-89206","identifiers":["EUVD-2026-89206","CVE-2026-102823","GHSA-47hw-gvq5-r2gm"]},"retained":false,"historicalAffected":[]},{"revision":"b9326344d18d4db08f9eed3610181b44","observedAt":"2026-10-25T04:17:26.915+00:00","statement":{"source":"nvd","id":"CVE-2026-102823","aliases":[],"title":"Russh is a Rust SSH client and server library. Prior to 0.63.1, client_read_authenticated in russh/src/client/encrypted.rs forwards CHANNEL_DATA, CHANNEL_EXTENDED_DATA, CHANNEL_EOF, CHANNEL_CLOSE, CHANNEL_OPEN_FAILURE, CHANNEL_SUCCESS, CHAN…","description":"Russh is a Rust SSH client and server library. Prior to 0.63.1, client_read_authenticated in russh/src/client/encrypted.rs forwards CHANNEL_DATA, CHANNEL_EXTENDED_DATA, CHANNEL_EOF, CHANNEL_CLOSE, CHANNEL_OPEN_FAILURE, CHANNEL_SUCCESS, CHANNEL_FAILURE, and CHANNEL_REQUEST subtypes exit-status, exit-signal, and xon-xoff to public client::Handler callbacks without confirming that the ChannelId belongs to a channel the client opened and established. A malicious SSH server can send lifecycle events for predicted, unopened, unconfirmed, or released channel identifiers, causing application panics or corrupting command completion and exit-code tracking. This issue is fixed in version 0.63.1.","state":0,"publishedAt":"2026-09-29T19:17:24.367+00:00","modifiedAt":"2026-10-02T13:17:25.65+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:H/A:N","score":7.5,"severity":"HIGH"}],"references":["https://github.com/Eugeny/russh/commit/3430fd26ecafc0dc3705210f5f39a9119fa22774","https://github.com/Eugeny/russh/releases/tag/v0.63.1","https://github.com/Eugeny/russh/security/advisories/GHSA-47hw-gvq5-r2gm"],"sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-102823","license":"NIST NVD usage terms; underlying source attribution retained","enrichment":{"sourceStatus":"Deferred","weaknesses":["CWE-20"],"productCriteria":[],"sourceDates":{"published":"2026-09-29T19:17:24.367","lastModified":"2026-10-02T13:17:25.650"},"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-2026-102823","identifiers":["CVE-2026-102823"]},"retained":false,"historicalAffected":[]},{"revision":"fdb333adddcf41e59afead91ce393fc4","observedAt":"2026-10-24T13:19:54.901+00:00","statement":{"source":"osv","id":"GHSA-47hw-gvq5-r2gm","aliases":["CVE-2026-102823"],"title":"russh: Client-side channel-scoped Handler callbacks fire for channel IDs the client never opened","description":"### Summary\nCVE-2026-68930 was fixed by adding `Session::is_established_channel()` in `russh/src/server/encrypted.rs`, which gates every channel-scoped SERVER-side message (CHANNEL_REQUEST, CHANNEL_DATA, CHANNEL_EOF, CHANNEL_CLOSE, CHANNEL_WINDOW_ADJUST, CHANNEL_EXTENDED_DATA) on `enc.channels.get(&channel).is_some_and(|c| c.confirmed)` before invoking any `Handler` callback. The identical validation was never added to the CLIENT side (`russh/src/client/encrypted.rs`), which processes channel-scoped messages sent by the SSH SERVER once the client has authenticated.\n\n### Details\nIn `client_read_authenticated` (`russh/src/client/encrypted.rs`, ~lines 431-757), for CHANNEL_DATA, CHANNEL_EXTENDED_DATA, CHANNEL_EOF, CHANNEL_CLOSE, CHANNEL_OPEN_FAILURE, CHANNEL_SUCCESS, CHANNEL_FAILURE, and the CHANNEL_REQUEST sub-types exit-status/exit-signal/xon-xoff, the code only optionally forwards the event to the internal per-channel mpsc sender via `if let Some(chan) = self.channels.get(&channel_num) { ... }` (a no-op if the channel is unknown), but then **unconditionally** calls the corresponding public `Handler` trait method (`client.data(...)`, `client.exit_status(...)`, `client.channel_close(...)`, `client.channel_success(...)`, etc.) regardless of whether `channel_num` corresponds to any channel the client ever opened or that was ever confirmed. Only CHANNEL_OPEN_CONFIRMATION (closes the connection with `Error::Inconsistent` if unknown) and CHANNEL_WINDOW_ADJUST (returns early with `Ok(())` if unknown) correctly validate channel existence before acting.\n\nCorroborating evidence this check was intended but never wired up: `crate::Error` defines a dedicated `WrongChannel` variant documented as \"Message received/sent on unopened channel\" (`russh/src/lib_inner.rs`, ~line 144-146), yet a repo-wide search shows this variant is never constructed or returned anywhere in the codebase — dead code left over from (or intended for) exactly this validation.\n\nBecause `Session::new_channel_id()` (`russh/src/session.rs`, ~line 708) allocates channel IDs sequentially starting at 1, a malicious or compromised SSH server can trivially predict the ID of the client's next channel and inject spoofed lifecycle events for it before or interleaved with the real channel-open exchange, or replay events for already-closed channel IDs.\n\n### PoC\nMany real-world consumers of russh-as-a-client (deployment/orchestration tools, CI runners connecting to build/bastion hosts, git-over-ssh style tooling, database/tunnel clients) implement the `client::Handler` trait directly and key their own state (e.g. `HashMap<ChannelId, CommandState>`, exit-code trackers, per-channel byte counters, completion futures) off the channel IDs the library hands them, trusting the documented contract that events like \"The remote process has exited\" (`exit_status`) or \"Called when the server closes a channel\" (`channel_close`) only fire for a channel the application itself opened.\n\nA malicious, MITM'd (via a compromised/rogue jump host the client is configured to trust), or simply hostile SSH server can send `SSH_MSG_CHANNEL_REQUEST` (exit-status/exit-signal), `SSH_MSG_CHANNEL_DATA`, `SSH_MSG_CHANNEL_CLOSE`, `SSH_MSG_CHANNEL_SUCCESS`/`FAILURE`, or `SSH_MSG_CHANNEL_OPEN_FAILURE` for an arbitrary/predicted/never-opened channel ID at any point after authentication completes. Because the library invokes the `Handler` callback unconditionally, this reaches application code with an ID it never registered.\n\n### Impact\n(1) A reliable, purely protocol-level trigger for an application panic/DoS in any client that indexes per-channel state by `ChannelId` without itself re-checking channel validity — the exact class of bug CVE-2026-68930 fixed server-side; and (2) lets the server spoof exit-status/exit-signal/close/success/failure notifications for a channel the client has not yet opened or has already released, desynchronizing the client's command-completion bookkeeping (e.g. reporting a forged exit code 0 for a not-yet-run remote command, or a premature `channel_close` before real output/exit-status has arrived) — a business-logic-level integrity violation of the SSH channel lifecycle that automation built on russh implicitly relies on.\n\nSuggested fix: add the same `is_established_channel()`-style gate already used in `server/encrypted.rs` to `client/encrypted.rs`'s `client_read_authenticated`, checking `self.channels.get(&channel_num)` before invoking any `Handler` callback (not just the mpsc forward), for every channel-scoped message type.\n\nFor credit/changelog purposes, please use: Yazan Balawneh, Cystack.ps","state":0,"publishedAt":"2026-09-30T23:27:17+00:00","modifiedAt":"2026-09-30T23:45:04.0166513+00:00","affected":[{"ecosystem":"crates.io","name":"russh","ranges":[{"type":"SEMVER","events":[{"kind":"introduced","version":"0"},{"kind":"fixed","version":"0.63.1"}]}],"versions":[],"rawVersionEvidence":null}],"metrics":[{"system":"CVSS_V3","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N","score":null,"severity":null},{"system":"Publisher rating","vector":null,"score":null,"severity":"HIGH"}],"references":["https://github.com/Eugeny/russh/security/advisories/GHSA-47hw-gvq5-r2gm","https://nvd.nist.gov/vuln/detail/CVE-2026-102823","https://github.com/Eugeny/russh/commit/3430fd26ecafc0dc3705210f5f39a9119fa22774","https://github.com/Eugeny/russh","https://github.com/Eugeny/russh/releases/tag/v0.63.1"],"sourceUrl":"https://github.com/advisories/GHSA-47hw-gvq5-r2gm","license":"GitHub Advisory Database · CC-BY-4.0","key":"osv:GHSA-47hw-gvq5-r2gm","identifiers":["GHSA-47hw-gvq5-r2gm","CVE-2026-102823"]},"retained":false,"historicalAffected":[]}],"coverage":[{"source":"cisa-kev:global","scope":"Complete CISA KEV catalog; all vendors. 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