CVE-2026-102821 (GCVE-0-2026-102821)

Vulnerability from cvelistv5 – Published: 2026-09-29 18:21 – Updated: 2026-09-29 18:21
VLAI
Title
Russh: Unbounded memory exhaustion via CHANNEL_OPEN flood during a client-stalled rekey
Summary
Russh is a Rust SSH client and server library. Prior to 0.63.2, an authenticated remote peer can send SSH_MSG_KEXINIT without the required SSH_MSG_KEX_ECDH_INIT and then flood SSH_MSG_CHANNEL_OPEN messages while SessionKexState::InProgress prevents priority_receiver in russh/src/server/session.rs from being drained. The server continues processing network input and enqueues a ChannelOpenReply for each request on an unbounded channel, allowing one connection to grow memory until the process is terminated. This issue is fixed in version 0.63.2.
Severity
6.5 (Medium)
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
CWE
  • CWE-400 - Uncontrolled Resource Consumption
  • CWE-770 - Allocation of Resources Without Limits or Throttling
Assigner
References
Impacted products
Vendor Product Version CPE status
Eugeny russh Affected: < 0.63.2
guessed Create a notification for this product.
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          "value": "Russh is a Rust SSH client and server library. Prior to 0.63.2, an authenticated remote peer can send SSH_MSG_KEXINIT without the required SSH_MSG_KEX_ECDH_INIT and then flood SSH_MSG_CHANNEL_OPEN messages while SessionKexState::InProgress prevents priority_receiver in russh/src/server/session.rs from being drained. The server continues processing network input and enqueues a ChannelOpenReply for each request on an unbounded channel, allowing one connection to grow memory until the process is terminated. This issue is fixed in version 0.63.2."
        }
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        {
          "descriptions": [
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              "description": "CWE-770: Allocation of Resources Without Limits or Throttling",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-09-29T18:21:21.858Z",
        "orgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
        "shortName": "GitHub_M"
      },
      "references": [
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          "tags": [
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          "url": "https://github.com/Eugeny/russh/security/advisories/GHSA-35g8-35p8-c8fw"
        },
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          "tags": [
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          "url": "https://github.com/Eugeny/russh/commit/a282af361ac99bc76b80876d1aae128e89dbf66b"
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        {
          "name": "https://github.com/Eugeny/russh/releases/tag/v0.63.2",
          "tags": [
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          "url": "https://github.com/Eugeny/russh/releases/tag/v0.63.2"
        }
      ],
      "source": {
        "advisory": "GHSA-35g8-35p8-c8fw",
        "discovery": "UNKNOWN"
      },
      "title": "Russh: Unbounded memory exhaustion via CHANNEL_OPEN flood during a client-stalled rekey"
    }
  },
  "cveMetadata": {
    "assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
    "assignerShortName": "GitHub_M",
    "cveId": "CVE-2026-102821",
    "datePublished": "2026-09-29T18:21:21.858Z",
    "dateReserved": "2026-09-29T17:25:25.265Z",
    "dateUpdated": "2026-09-29T18:21:21.858Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
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                "vendor": "Eugeny",
                "versions": [
                  {
                    "status": "affected",
                    "version": "\u003c 0.63.2"
                  }
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        ],
        "cveTags": [],
        "descriptions": [
          {
            "lang": "en",
            "value": "Russh is a Rust SSH client and server library. Prior to 0.63.2, an authenticated remote peer can send SSH_MSG_KEXINIT without the required SSH_MSG_KEX_ECDH_INIT and then flood SSH_MSG_CHANNEL_OPEN messages while SessionKexState::InProgress prevents priority_receiver in russh/src/server/session.rs from being drained. The server continues processing network input and enqueues a ChannelOpenReply for each request on an unbounded channel, allowing one connection to grow memory until the process is terminated. This issue is fixed in version 0.63.2."
          }
        ],
        "id": "CVE-2026-102821",
        "lastModified": "2026-09-29T19:17:24.140",
        "metrics": {
          "cvssMetricV31": [
            {
              "cvssData": {
                "attackComplexity": "LOW",
                "attackVector": "NETWORK",
                "availabilityImpact": "HIGH",
                "baseScore": 6.5,
                "baseSeverity": "MEDIUM",
                "confidentialityImpact": "NONE",
                "integrityImpact": "NONE",
                "privilegesRequired": "LOW",
                "scope": "UNCHANGED",
                "userInteraction": "NONE",
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        "published": "2026-09-29T19:17:23.993",
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            "url": "https://github.com/Eugeny/russh/commit/a282af361ac99bc76b80876d1aae128e89dbf66b"
          },
          {
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            "url": "https://github.com/Eugeny/russh/releases/tag/v0.63.2"
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            "url": "https://github.com/Eugeny/russh/security/advisories/GHSA-35g8-35p8-c8fw"
          }
        ],
        "sourceIdentifier": "security-advisories@github.com",
        "vulnStatus": "Deferred",
        "weaknesses": [
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              {
                "lang": "en",
                "value": "CWE-400"
              },
              {
                "lang": "en",
                "value": "CWE-770"
              }
            ],
            "source": "security-advisories@github.com",
            "type": "Primary"
          }
        ]
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    },
    "redhat_vex": {
      "aggregate_severity": "Moderate",
      "current_release_date": "2026-09-29T19:27:29+00:00",
      "cve": "CVE-2026-102821",
      "id": "CVE-2026-102821",
      "initial_release_date": "2026-09-29T18:21:21.858000+00:00",
      "product_status:known_affected": "1",
      "source": "Red Hat CSAF VEX",
      "status": "final",
      "title": "russh: russh: Denial of Service via unbounded memory exhaustion during stalled key renegotiation",
      "url": "https://security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-102821.json",
      "version": "3"
    }
  }
}



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