{"id":"CVE-2026-102822","revision":null,"records":[{"revision":"44a9a1cdd73d4217a747536fd8e240d8","observedAt":"2026-10-23T15:48:27.903+00:00","statement":{"source":"cve-program","id":"CVE-2026-102822","aliases":[],"title":"russh: negotiating a MAC-requiring block cipher (CTR/CBC) with mac=none causes a slice-index-out-of-range panic","description":"Russh is a Rust SSH client and server library. Prior to 0.63.1, a connection configured to permit mac=none can negotiate it with a MAC-requiring CTR or CBC block cipher because the selection logic validates needs_mac() only when MAC selection fails. A remote peer can then send a packet with a decrypted length of zero, causing russh/src/cipher/mod.rs to shrink the previously read block before indexing buffer.buffer[16..], which panics and terminates the connection task. This issue is fixed in version 0.63.1.","state":0,"publishedAt":"2026-09-29T18:23:28.061+00:00","modifiedAt":"2026-09-29T19:53:30.291+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:H/PR:N/UI:N/S:U/C:N/I:N/A:L","score":3.7,"severity":"LOW"}],"references":["https://github.com/Eugeny/russh/security/advisories/GHSA-p8qx-h547-fjw9","https://github.com/Eugeny/russh/commit/2885385abfee279092a41d80c6cb6ac367353159","https://github.com/Eugeny/russh/releases/tag/v0.63.1"],"sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-102822","license":"CVE Program Terms of Use","key":"cve-program:CVE-2026-102822","identifiers":["CVE-2026-102822"]},"retained":false,"historicalAffected":[]},{"revision":"b7d7adea9a2e4cebbda9dce94754a48b","observedAt":"2026-11-11T05:29:27.781+00:00","statement":{"source":"euvd","id":"EUVD-2026-89205","aliases":["CVE-2026-102822","GHSA-p8qx-h547-fjw9"],"title":"Russh is a Rust SSH client and server library. Prior to 0.63.1, a connection configured to permit mac=none can negotiate it with a MAC-requiring CTR or CBC block cipher because the selection logic validates needs_mac() only when MAC selecti…","description":"Russh is a Rust SSH client and server library. Prior to 0.63.1, a connection configured to permit mac=none can negotiate it with a MAC-requiring CTR or CBC block cipher because the selection logic validates needs_mac() only when MAC selection fails. A remote peer can then send a packet with a decrypted length of zero, causing russh/src/cipher/mod.rs to shrink the previously read block before indexing buffer.buffer[16..], which panics and terminates the connection task. 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:H/PR:N/UI:N/S:U/C:N/I:N/A:L","score":3.7,"severity":null}],"references":["https://github.com/Eugeny/russh/security/advisories/GHSA-p8qx-h547-fjw9","https://github.com/Eugeny/russh/commit/2885385abfee279092a41d80c6cb6ac367353159","https://github.com/Eugeny/russh/releases/tag/v0.63.1"],"sourceUrl":"https://euvd.enisa.europa.eu/vulnerability/EUVD-2026-89205","license":"ENISA EUVD · source terms and attribution apply","enrichment":{"sourceStatus":null,"weaknesses":[],"productCriteria":[],"sourceDates":{"datePublished":"Sep 29, 2026, 6:23:28 PM","dateUpdated":"Sep 29, 2026, 7:53:30 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-2026-89205","identifiers":["EUVD-2026-89205","CVE-2026-102822","GHSA-p8qx-h547-fjw9"]},"retained":false,"historicalAffected":[]},{"revision":"6e0785da728b4e35a4b77e95d432900c","observedAt":"2026-10-25T04:17:26.915+00:00","statement":{"source":"nvd","id":"CVE-2026-102822","aliases":[],"title":"Russh is a Rust SSH client and server library. Prior to 0.63.1, a connection configured to permit mac=none can negotiate it with a MAC-requiring CTR or CBC block cipher because the selection logic validates needs_mac() only when MAC selecti…","description":"Russh is a Rust SSH client and server library. Prior to 0.63.1, a connection configured to permit mac=none can negotiate it with a MAC-requiring CTR or CBC block cipher because the selection logic validates needs_mac() only when MAC selection fails. A remote peer can then send a packet with a decrypted length of zero, causing russh/src/cipher/mod.rs to shrink the previously read block before indexing buffer.buffer[16..], which panics and terminates the connection task. This issue is fixed in version 0.63.1.","state":0,"publishedAt":"2026-09-29T19:17:24.19+00:00","modifiedAt":"2026-09-29T20:17:17.673+00:00","affected":[],"metrics":[{"system":"CVSS 3.1 · security-advisories@github.com · Secondary","vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L","score":3.7,"severity":"LOW"}],"references":["https://github.com/Eugeny/russh/commit/2885385abfee279092a41d80c6cb6ac367353159","https://github.com/Eugeny/russh/releases/tag/v0.63.1","https://github.com/Eugeny/russh/security/advisories/GHSA-p8qx-h547-fjw9"],"sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-102822","license":"NIST NVD usage terms; underlying source attribution retained","enrichment":{"sourceStatus":"Deferred","weaknesses":["CWE-129"],"productCriteria":[],"sourceDates":{"published":"2026-09-29T19:17:24.190","lastModified":"2026-09-29T20:17:17.673"},"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-2026-102822","identifiers":["CVE-2026-102822"]},"retained":false,"historicalAffected":[]},{"revision":"ce533b08b65747c7a052a5dc84822f16","observedAt":"2026-10-24T13:19:54.901+00:00","statement":{"source":"osv","id":"GHSA-p8qx-h547-fjw9","aliases":["CVE-2026-102822"],"title":"russh: negotiating a MAC-requiring block cipher (CTR/CBC) with mac=none causes a slice-index-out-of-range panic","description":"### Summary\n`SshBlockCipher` implementations (AES-CBC, AES-CTR, 3DES-CBC, etc.) report `needs_mac() == true`, meaning they are documented/intended to always be paired with a separate integrity MAC. However, key-exchange negotiation only checks `needs_mac()` inside the *fallback* branch of MAC algorithm selection (used when no common MAC algorithm exists). If both peers' preferred MAC lists simply contain `none` and it is successfully negotiated through the normal selection path, nothing rejects pairing `none` with a cipher that requires a MAC. Once negotiated, a single crafted packet from either peer causes `cipher::read()` to shrink an already-allocated buffer below the number of bytes it is about to index, causing a Rust slice-index-out-of-range panic and killing that connection's task.\n\n### Details\nIn `russh/src/cipher/mod.rs`, `read()` for a block cipher:\n1. Reads `packet_length_to_read_for_block_length()` bytes up front (16 bytes for any `SshBlockCipher`) into `buffer.buffer`.\n2. Decrypts the first block to recover the plaintext packet-length field `len`.\n3. Computes `buffer.len = len + cipher.tag_len()`.\n4. Calls `buffer.buffer.resize(buffer.len + 4, 0)`.\n5. Immediately indexes `buffer.buffer[16..]` (via the constant used for the first block read) to continue decrypting/reading the rest of the packet.\n\nWhen the negotiated MAC is `none`, `tag_len() == 0`. If the attacker (or a MITM holding the session key, or simply the accepting peer testing a hostile client) sends a packet whose *decrypted* length field is `0`, then `buffer.len = 0` and `resize(0 + 4, 0)` **shrinks** the buffer that was already grown to 16 bytes in step 1 down to 4 bytes. The subsequent slice operation `buffer.buffer[16..]` then panics with `range start index 16 out of range for slice of length 4`.\n\nThe file already defines a `MINIMUM_PACKET_LEN` constant, but it is only consulted on the *write*/padding side, never on the read path — so nothing prevents an incoming packet from declaring a length shorter than the bytes already buffered.\n\nNegotiation gap: `negotiation.rs`'s `Select` MAC-selection logic only special-cases `needs_mac()` when negotiation would otherwise *fail* (no common MAC), substituting `none` only if the cipher does not need one. It never re-validates the case where `none` is a common/successfully-negotiated MAC on both sides regardless of what the chosen cipher requires. So an application (or a malicious peer, since negotiation is attacker-influenced on one side) that includes `none` in its own preferred MAC list — while still allowing the default CTR/CBC cipher suite — ends up with an invalid, panic-inducing combination that the library itself should refuse.\n\n### PoC\n1. Configure one side's `Preferred` config to include `mac::NONE` in the MAC list (this is a supported, non-default configuration exposed by the crate's public `Preferred` API — used e.g. for legacy/interop compatibility), while leaving the default cipher list (which includes `aes256-ctr`/`aes256-cbc`) untouched.\n2. Complete a normal key exchange; negotiation lands on `{cipher: aes*-ctr (or -cbc), mac: none}` because `none` is present and preferred/common on both sides, and nothing during negotiation rejects this pairing.\n3. From the peer, send one transport packet whose decrypted packet-length field is `0` (trivial to construct once the session keys are known to that peer, or for the peer that legitimately owns the connection to simply hand-craft, e.g. a modified client for testing).\n4. `cipher::read()` on the receiving side panics: `range start index 16 out of range for slice of length 4`.\n5. Because each connection is handled in its own `tokio::spawn`'ed task (see the per-connection `select!` loop that calls into `cipher::read()`), the panic unwinds only that task by default, but it unconditionally terminates that SSH connection/session — a working, currently-unauthenticated, already-established connection is killed with no attacker interaction beyond the one crafted packet, and the check runs on every inbound packet including pre-auth ones.\n\n\n### Impact\nDenial of service: a remote peer that can influence MAC preference negotiation (or a MITM in possession of the session key) can crash any individual SSH connection/session that ends up negotiating a block cipher together with `mac=none`, with a single crafted packet, pre-authentication. This does not affect the process as a whole (panic is scoped to that connection's task under `panic=unwind`), and does require a non-default configuration that permits `none` as a preferred MAC — hence Low severity.\n\n### Suggested fix\nIn the MAC-selection logic in `negotiation.rs`, reject (or force substitution of) `mac::NONE` whenever the negotiated cipher's `needs_mac()` is `true`, regardless of *how* `none` came to be selected — not only in the \"no common MAC\" fallback branch. Defensively, `cipher::read()` could also refuse to shrink a buffer below the number of bytes already consumed for the length-field block, returning a protocol error instead of resizing blindly.\n\nFor credit/changelog purposes, please use: Yazan Balawneh, Cystack.ps","state":0,"publishedAt":"2026-09-30T23:27:30+00:00","modifiedAt":"2026-09-30T23:45:04.0100013+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:H/PR:N/UI:N/S:U/C:N/I:N/A:L","score":null,"severity":null},{"system":"Publisher rating","vector":null,"score":null,"severity":"LOW"}],"references":["https://github.com/Eugeny/russh/security/advisories/GHSA-p8qx-h547-fjw9","https://nvd.nist.gov/vuln/detail/CVE-2026-102822","https://github.com/Eugeny/russh/commit/2885385abfee279092a41d80c6cb6ac367353159","https://github.com/Eugeny/russh","https://github.com/Eugeny/russh/releases/tag/v0.63.1"],"sourceUrl":"https://github.com/advisories/GHSA-p8qx-h547-fjw9","license":"GitHub Advisory Database · CC-BY-4.0","key":"osv:GHSA-p8qx-h547-fjw9","identifiers":["GHSA-p8qx-h547-fjw9","CVE-2026-102822"]},"retained":false,"historicalAffected":[]}],"coverage":[{"source":"cisa-kev:global","scope":"Complete CISA KEV catalog; all vendors. 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