Vulnerability-Lookup

GHSA-G6XM-F9XP-QQ35

Vulnerability from github – Published: 2026-09-30 23:26 – Updated: 2026-09-30 23:26

Summary

Russh: Configured server auth-attempt cap is not enforced in the USERAUTH_REQUEST runtime path

Details

Affected versions and vulnerable location

Confirmed present on default branch main at HEAD 0089c89c94753bebbec12b956c07a1cd38740379.
Crate version at HEAD: 0.62.4.
Vulnerable locations on current default branch:
russh/src/server/mod.rs:91 (pub max_auth_attempts: usize)
russh/src/server/mod.rs:121 (default max_auth_attempts: 10)
russh/src/server/encrypted.rs:89 (USERAUTH_REQUEST dispatch into auth handler path)
russh/src/server/encrypted.rs:98 (self.common.auth_attempts += 1)
russh/src/server/encrypted.rs:53 (only runtime read of auth_attempts, used for initial reject timing, not attempt limiting)
Default-branch history check did not show a newer merged commit adding enforcement against config.max_auth_attempts.

Reachability trace verified

Entry point: exported server API server::run_stream in russh/src/server/mod.rs:1049.
Session run loop in russh/src/server/session.rs processes incoming packets and calls reply(...) (server/session.rs:725).
reply forwards encrypted packets to session.server_read_encrypted(...) (server/mod.rs:1221).
server_read_encrypted routes USERAUTH_REQUEST to enc.server_read_auth_request(...) (server/encrypted.rs:89).
On each request, self.common.auth_attempts += 1 executes (server/encrypted.rs:98).
No comparison against self.common.config.max_auth_attempts is present in this runtime flow.

PoC

Reproduction steps and observed output

I did not run a full server process in this environment because Rust tooling is unavailable. I verified the issue from source and command output on the audited tree.

Show where max_auth_attempts appears:

rtk rg -n "max_auth_attempts" .scratch/russh/russh/src/server/mod.rs .scratch/russh/russh/src/server/encrypted.rs .scratch/russh/russh/src/server/session.rs

Observed:

.scratch/russh/russh/src/server/mod.rs:91:    pub max_auth_attempts: usize,
.scratch/russh/russh/src/server/mod.rs:121:            max_auth_attempts: 10,
.scratch/russh/russh/src/server/mod.rs:148:            .field("max_auth_attempts", &self.max_auth_attempts)

Show runtime auth-attempt handling:

rtk rg -n "auth_attempts == 0|auth_attempts \\+= 1" .scratch/russh/russh/src/server/encrypted.rs

Observed:

53:        let initial_none_rejection_wait_until = if self.common.auth_attempts == 0 {
98:                self.common.auth_attempts += 1;

Show production entrypoint-to-auth path references:

rtk rg -n "pub async fn run_stream|match reply\\(|server_read_encrypted\\(|server_read_auth_request\\(" .scratch/russh/russh/src/server/mod.rs .scratch/russh/russh/src/server/session.rs .scratch/russh/russh/src/server/encrypted.rs

Observed:

.scratch/russh/russh/src/server/encrypted.rs:89:                enc.server_read_auth_request(
.scratch/russh/russh/src/server/session.rs:725:                            match reply(&mut self, &mut handler, &mut pkt).await {
.scratch/russh/russh/src/server/mod.rs:1049:pub async fn run_stream<H, R>(
.scratch/russh/russh/src/server/mod.rs:1221:    session.server_read_encrypted(handler, pkt).await

Toolchain check:

cargo --version

Observed:

/bin/bash: line 1: cargo: command not found

Impact

Attacker model

Attacker: unauthenticated remote client with TCP reachability to a russh-backed SSH service.
Preconditions: deployer expects server::Config.max_auth_attempts to cap attempts.
Impact: repeated USERAUTH_REQUEST attempts continue for a single connection beyond configured limit, increasing online guessing opportunity and backend auth workload.

Suggested fix

Enforce max_auth_attempts in the USERAUTH_REQUEST branch before invoking auth-method handlers, and fail closed once threshold is reached.

Concrete patch direction in russh/src/server/encrypted.rs:

if self.common.config.max_auth_attempts > 0
    && self.common.auth_attempts >= self.common.config.max_auth_attempts
{
    self.common.disconnect(
        Disconnect::NoMoreAuthMethodsAvailable,
        "Too many authentication attempts",
        "",
    )?;
    return Ok(());
}

How it was found and a note on tooling

The researcher synthesized three lens outputs, then revalidated each claim against current main: source presence and commit history, advisory overlap checks in both GitHub advisories and OSV, entrypoint-to-sink reachability, attacker-model realism, and execution-claim integrity. The researcher used gh, git, rg, and direct source inspection under .scratch/russh. Because Rust tooling is unavailable in this worker, this report is intentionally marked source-only.

AI assistance was used while investigating this and while drafting this report. The finding was verified by reading the cited code at HEAD. The vulnerability was not executed it, and that limit is stated plainly above rather than left implied.

Credits: arpitjain099.

Severity

3.7 (Low)


                  
                    CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N

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{
  "affected": [
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 0.62.5"
      },
      "package": {
        "ecosystem": "crates.io",
        "name": "russh"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "0.62.6"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-102825"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-307"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-09-30T23:26:17Z",
    "nvd_published_at": "2026-09-29T19:17:24Z",
    "severity": "LOW"
  },
  "details": "### Details\n\n#### Affected versions and vulnerable location\n\n- Confirmed present on default branch `main` at HEAD `0089c89c94753bebbec12b956c07a1cd38740379`.\n- Crate version at HEAD: `0.62.4`.\n- Vulnerable locations on current default branch:\n  - `russh/src/server/mod.rs:91` (`pub max_auth_attempts: usize`)\n  - `russh/src/server/mod.rs:121` (default `max_auth_attempts: 10`)\n  - `russh/src/server/encrypted.rs:89` (`USERAUTH_REQUEST` dispatch into auth handler path)\n  - `russh/src/server/encrypted.rs:98` (`self.common.auth_attempts += 1`)\n  - `russh/src/server/encrypted.rs:53` (only runtime read of `auth_attempts`, used for initial reject timing, not attempt limiting)\n- Default-branch history check did not show a newer merged commit adding enforcement against `config.max_auth_attempts`.\n\n#### Reachability trace verified\n\n1. Entry point: exported server API `server::run_stream` in `russh/src/server/mod.rs:1049`.\n2. Session run loop in `russh/src/server/session.rs` processes incoming packets and calls `reply(...)` (`server/session.rs:725`).\n3. `reply` forwards encrypted packets to `session.server_read_encrypted(...)` (`server/mod.rs:1221`).\n4. `server_read_encrypted` routes `USERAUTH_REQUEST` to `enc.server_read_auth_request(...)` (`server/encrypted.rs:89`).\n5. On each request, `self.common.auth_attempts += 1` executes (`server/encrypted.rs:98`).\n6. No comparison against `self.common.config.max_auth_attempts` is present in this runtime flow.\n\n### PoC\n\n#### Reproduction steps and observed output\n\nI did not run a full server process in this environment because Rust tooling is unavailable. I verified the issue from source and command output on the audited tree.\n\n1. Show where `max_auth_attempts` appears:\n\n```bash\nrtk rg -n \"max_auth_attempts\" .scratch/russh/russh/src/server/mod.rs .scratch/russh/russh/src/server/encrypted.rs .scratch/russh/russh/src/server/session.rs\n```\n\nObserved:\n\n```text\n.scratch/russh/russh/src/server/mod.rs:91:    pub max_auth_attempts: usize,\n.scratch/russh/russh/src/server/mod.rs:121:            max_auth_attempts: 10,\n.scratch/russh/russh/src/server/mod.rs:148:            .field(\"max_auth_attempts\", \u0026self.max_auth_attempts)\n```\n\n2. Show runtime auth-attempt handling:\n\n```bash\nrtk rg -n \"auth_attempts == 0|auth_attempts \\\\+= 1\" .scratch/russh/russh/src/server/encrypted.rs\n```\n\nObserved:\n\n```text\n53:        let initial_none_rejection_wait_until = if self.common.auth_attempts == 0 {\n98:                self.common.auth_attempts += 1;\n```\n\n3. Show production entrypoint-to-auth path references:\n\n```bash\nrtk rg -n \"pub async fn run_stream|match reply\\\\(|server_read_encrypted\\\\(|server_read_auth_request\\\\(\" .scratch/russh/russh/src/server/mod.rs .scratch/russh/russh/src/server/session.rs .scratch/russh/russh/src/server/encrypted.rs\n```\n\nObserved:\n\n```text\n.scratch/russh/russh/src/server/encrypted.rs:89:                enc.server_read_auth_request(\n.scratch/russh/russh/src/server/session.rs:725:                            match reply(\u0026mut self, \u0026mut handler, \u0026mut pkt).await {\n.scratch/russh/russh/src/server/mod.rs:1049:pub async fn run_stream\u003cH, R\u003e(\n.scratch/russh/russh/src/server/mod.rs:1221:    session.server_read_encrypted(handler, pkt).await\n```\n\n4. Toolchain check:\n\n```bash\ncargo --version\n```\n\nObserved:\n\n```text\n/bin/bash: line 1: cargo: command not found\n```\n\n### Impact\n\n#### Attacker model\n\n- Attacker: unauthenticated remote client with TCP reachability to a russh-backed SSH service.\n- Preconditions: deployer expects `server::Config.max_auth_attempts` to cap attempts.\n- Impact: repeated `USERAUTH_REQUEST` attempts continue for a single connection beyond configured limit, increasing online guessing opportunity and backend auth workload.\n\n### Suggested fix\n\nEnforce `max_auth_attempts` in the `USERAUTH_REQUEST` branch before invoking auth-method handlers, and fail closed once threshold is reached.\n\nConcrete patch direction in `russh/src/server/encrypted.rs`:\n\n```rust\nif self.common.config.max_auth_attempts \u003e 0\n    \u0026\u0026 self.common.auth_attempts \u003e= self.common.config.max_auth_attempts\n{\n    self.common.disconnect(\n        Disconnect::NoMoreAuthMethodsAvailable,\n        \"Too many authentication attempts\",\n        \"\",\n    )?;\n    return Ok(());\n}\n```\n\n### How it was found and a note on tooling\n\nThe researcher synthesized three lens outputs, then revalidated each claim against current `main`: source presence and commit history, advisory overlap checks in both GitHub advisories and OSV, entrypoint-to-sink reachability, attacker-model realism, and execution-claim integrity. The researcher used `gh`, `git`, `rg`, and direct source inspection under `.scratch/russh`. Because Rust tooling is unavailable in this worker, this report is intentionally marked `source-only`.\n\nAI assistance was used while investigating this and while drafting this report. The finding was verified by reading the cited code at HEAD. The vulnerability was not executed it, and that limit is stated plainly above rather than left implied.\n\nCredits: arpitjain099.",
  "id": "GHSA-g6xm-f9xp-qq35",
  "modified": "2026-09-30T23:26:17Z",
  "published": "2026-09-30T23:26:17Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/Eugeny/russh/security/advisories/GHSA-g6xm-f9xp-qq35"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-102825"
    },
    {
      "type": "WEB",
      "url": "https://github.com/Eugeny/russh/commit/f8fd0b11a393364dc7f01a182482d86adafdd653"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/Eugeny/russh"
    },
    {
      "type": "WEB",
      "url": "https://github.com/Eugeny/russh/releases/tag/v0.62.6"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Russh: Configured server auth-attempt cap is not enforced in the USERAUTH_REQUEST runtime path"
}

CVE-2026-102825 (GCVE-0-2026-102825)

Vulnerability from cvelistv5 – Published: 2026-09-29 18:31 – Updated: 2026-09-30 19:29

Title

Russh: Configured server auth-attempt cap is not enforced in the USERAUTH_REQUEST runtime path

Summary

Russh is a Rust SSH client and server library. Prior to 0.62.6, the USERAUTH_REQUEST path reached from server::run_stream in russh/src/server/encrypted.rs increments self.common.auth_attempts but never compares it with server::Config.max_auth_attempts. An unauthenticated remote client can continue submitting authentication requests on one connection beyond the configured cap, bypassing the deployment's attempt-limiting policy and increasing online guessing opportunity and backend authentication workload. This issue is fixed in version 0.62.6.

Severity

3.7 (Low)


                        
                          CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N

SSVC

Exploitation: poc Automatable: no Technical Impact: partial

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-09-30 19:29 UTC

CWE

CWE-307 - Improper Restriction of Excessive Authentication Attempts

Assigner

GitHub_M mitre root Scorecard

References

3 references

URL	Tags
https://github.com/Eugeny/russh/security/advisori…	x_refsource_CONFIRM
https://github.com/Eugeny/russh/commit/f8fd0b11a3…	x_refsource_MISC
https://github.com/Eugeny/russh/releases/tag/v0.62.6	x_refsource_MISC

Impacted products

1 product

Vendor	Product	Version
Eugeny	russh	Affected: < 0.62.6

Show details on NVD website

JSON

To clipboard

{
  "containers": {
    "adp": [
      {
        "metrics": [
          {
            "other": {
              "content": {
                "id": "CVE-2026-102825",
                "options": [
                  {
                    "Exploitation": "poc"
                  },
                  {
                    "Automatable": "no"
                  },
                  {
                    "Technical Impact": "partial"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-09-30T19:29:11.461462Z",
                "version": "2.0.3"
              },
              "type": "ssvc"
            }
          }
        ],
        "providerMetadata": {
          "dateUpdated": "2026-09-30T19:29:26.432Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
        "references": [
          {
            "tags": [
              "exploit"
            ],
            "url": "https://github.com/Eugeny/russh/security/advisories/GHSA-g6xm-f9xp-qq35"
          }
        ],
        "title": "CISA ADP Vulnrichment"
      }
    ],
    "cna": {
      "affected": [
        {
          "product": "russh",
          "vendor": "Eugeny",
          "versions": [
            {
              "status": "affected",
              "version": "\u003c 0.62.6"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "Russh is a Rust SSH client and server library. Prior to 0.62.6, the USERAUTH_REQUEST path reached from server::run_stream in russh/src/server/encrypted.rs increments self.common.auth_attempts but never compares it with server::Config.max_auth_attempts. An unauthenticated remote client can continue submitting authentication requests on one connection beyond the configured cap, bypassing the deployment\u0027s attempt-limiting policy and increasing online guessing opportunity and backend authentication workload. This issue is fixed in version 0.62.6."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "attackComplexity": "HIGH",
            "attackVector": "NETWORK",
            "availabilityImpact": "NONE",
            "baseScore": 3.7,
            "baseSeverity": "LOW",
            "confidentialityImpact": "LOW",
            "integrityImpact": "NONE",
            "privilegesRequired": "NONE",
            "scope": "UNCHANGED",
            "userInteraction": "NONE",
            "vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N",
            "version": "3.1"
          }
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-307",
              "description": "CWE-307: Improper Restriction of Excessive Authentication Attempts",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-09-29T18:31:32.393Z",
        "orgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
        "shortName": "GitHub_M"
      },
      "references": [
        {
          "name": "https://github.com/Eugeny/russh/security/advisories/GHSA-g6xm-f9xp-qq35",
          "tags": [
            "x_refsource_CONFIRM"
          ],
          "url": "https://github.com/Eugeny/russh/security/advisories/GHSA-g6xm-f9xp-qq35"
        },
        {
          "name": "https://github.com/Eugeny/russh/commit/f8fd0b11a393364dc7f01a182482d86adafdd653",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/Eugeny/russh/commit/f8fd0b11a393364dc7f01a182482d86adafdd653"
        },
        {
          "name": "https://github.com/Eugeny/russh/releases/tag/v0.62.6",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/Eugeny/russh/releases/tag/v0.62.6"
        }
      ],
      "source": {
        "advisory": "GHSA-g6xm-f9xp-qq35",
        "discovery": "UNKNOWN"
      },
      "title": "Russh: Configured server auth-attempt cap is not enforced in the USERAUTH_REQUEST runtime path"
    }
  },
  "cveMetadata": {
    "assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
    "assignerShortName": "GitHub_M",
    "cveId": "CVE-2026-102825",
    "datePublished": "2026-09-29T18:31:32.393Z",
    "dateReserved": "2026-09-29T17:25:25.265Z",
    "dateUpdated": "2026-09-30T19:29:26.432Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}

Sightings

Author	Source	Type	Date	Other

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.

Related by attack behaviour

Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.

Action not permitted

GHSA-G6XM-F9XP-QQ35

Details

Affected versions and vulnerable location

Reachability trace verified

PoC

Reproduction steps and observed output

Impact

Attacker model

Suggested fix

How it was found and a note on tooling

CVE-2026-102825 (GCVE-0-2026-102825)

Tags

Sightings

Nomenclature

Related by attack behaviour