russh's SSH agent server is susceptible to unbound allocations via repeated SSH_AGENT_CONSTRAIN_CONFIRM messages

{
  "id": "c4f1f1521c2503cfc0300f9eeb118da6c50dcab0c3aa28e8bb4a5d1e1d5610de",
  "url": "https://www.cve.org/CVERecord?id=CVE-2026-116696",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "russh's SSH agent server is susceptible to unbound allocations via repeated SSH_AGENT_CONSTRAIN_CONFIRM messages",
    "summary": "russh is a Rust SSH client and server library that includes an SSH agent protocol implementation. Prior to 0.65.0, russh::keys::agent::server::serve in russh/src/keys/agent/server.rs accepts repeated SSH_AGENT_CONSTRAIN_CONFIRM records while adding a key and appends every Constraint::Confirm record to the key's retained constraint vector without a count or memory limit. A process that can connect to the agent socket, including the remote side of a forwarded agent session, can repeatedly add constrained keys and cause renewable memory growth that persists for the process lifetime because keys without a lifetime constraint do not expire. This issue is fixed in version 0.65.0.",
    "evidence": "cve:CVE-2026-116696",
    "products": [
      {
        "name": {
          "value": "russh",
          "evidence": "/containers/cna/affected/0/product"
        },
        "prerequisites": [],
        "fixed_versions": [],
        "affected_versions": []
      }
    ],
    "severity": "low",
    "structured": {
      "id": "CVE-2026-116696",
      "aliases": [
        "CVE-2026-116696"
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "scope": "UNCHANGED",
            "version": "3.1",
            "baseScore": 3.3,
            "attackVector": "LOCAL",
            "baseSeverity": "LOW",
            "vectorString": "CVSS:3.1/AV:L/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": "< 0.65.0"
            }
          ]
        }
      ],
      "modified": "2026-10-27T20:14:32.973Z",
      "provider": "cve",
      "references": [
        "https://github.com/Eugeny/russh/security/advisories/GHSA-9wfm-jcj8-jfv9",
        "https://github.com/Eugeny/russh/commit/23aa5d28fe9601c5bdfe9e60b7ec5d4f882c3de6",
        "https://github.com/Eugeny/russh/releases/tag/v0.65.0"
      ],
      "provider_metadata": {
        "cna": {
          "orgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
          "shortName": "GitHub_M",
          "dateUpdated": "2026-10-27T20:14:32.973Z"
        }
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-116696",
        "evidence": "/cveMetadata/cveId"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/containers/cna/metrics"
  },
  "source_id": "core-cve",
  "document_id": 398627,
  "published_at": "2026-10-27T20:14:32.973+00:00"
}