russh: peer-declared zero maximum packet size permanently stalls channel writes (silent AsyncWrite hang)

{
  "id": "823fbb1dfbe3d94bec0352aff0bb8554d40d280aa0b53025707e1253e76e26bf",
  "url": "https://www.cve.org/CVERecord?id=CVE-2026-116774",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "russh: peer-declared zero maximum packet size permanently stalls channel writes (silent AsyncWrite hang)",
    "summary": "russh is a Rust SSH client and server library that includes an SSH agent protocol implementation. From 0.60.0 until 0.65.0, channel-open parsing accepts a peer-declared maximum_packet_size of zero and passes it into ChannelTx::poll_writable in russh/src/channels/io/tx.rs. The Channel::data, Channel::make_writer, and Channel::into_stream asynchronous write paths then calculate a writable size of zero and remain pending forever because window adjustments cannot satisfy a static zero packet maximum. An authenticated client can strand server writes, and a malicious server can strand client writes, allowing affected tasks, channels, and connections to accumulate without surfacing an error. This issue is fixed in version 0.65.0.",
    "evidence": "cve:CVE-2026-116774",
    "products": [
      {
        "name": {
          "value": "russh",
          "evidence": "/containers/cna/affected/0/product"
        },
        "prerequisites": [],
        "fixed_versions": [],
        "affected_versions": []
      }
    ],
    "severity": "medium",
    "structured": {
      "id": "CVE-2026-116774",
      "aliases": [
        "CVE-2026-116774"
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "scope": "UNCHANGED",
            "version": "3.1",
            "baseScore": 4.3,
            "attackVector": "NETWORK",
            "baseSeverity": "MEDIUM",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L",
            "integrityImpact": "NONE",
            "userInteraction": "NONE",
            "attackComplexity": "LOW",
            "availabilityImpact": "LOW",
            "privilegesRequired": "LOW",
            "confidentialityImpact": "NONE"
          }
        }
      ],
      "affected": [
        {
          "vendor": "Eugeny",
          "product": "russh",
          "versions": [
            {
              "status": "affected",
              "version": ">= 0.60.0, < 0.65.0"
            }
          ]
        }
      ],
      "modified": "2026-10-28T16:13:18.607Z",
      "provider": "cve",
      "references": [
        "https://github.com/Eugeny/russh/security/advisories/GHSA-fw5c-8223-6h42",
        "https://github.com/Eugeny/russh/commit/39cb9dbaa37caf555d34c6c22efa3bbbff9e186c",
        "https://github.com/Eugeny/russh/releases/tag/v0.65.0"
      ],
      "provider_metadata": {
        "adp": [
          {
            "title": "CISA ADP Vulnrichment",
            "metrics": [
              {
                "other": {
                  "type": "ssvc",
                  "content": {
                    "id": "CVE-2026-116774",
                    "role": "CISA Coordinator",
                    "options": [
                      {
                        "Exploitation": "none"
                      },
                      {
                        "Automatable": "no"
                      },
                      {
                        "Technical Impact": "partial"
                      }
                    ],
                    "version": "2.0.3",
                    "timestamp": "2026-10-28T14:34:53.983359Z"
                  }
                }
              }
            ],
            "providerMetadata": {
              "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
              "shortName": "CISA-ADP",
              "dateUpdated": "2026-10-28T16:13:18.607Z"
            }
          }
        ],
        "cna": {
          "orgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
          "shortName": "GitHub_M",
          "dateUpdated": "2026-10-27T20:25:26.914Z"
        }
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-116774",
        "evidence": "/cveMetadata/cveId"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/containers/cna/metrics"
  },
  "source_id": "core-cve",
  "document_id": 460244,
  "published_at": "2026-10-27T20:25:26.914+00:00"
}