CVE-2026-7829 (GCVE-0-2026-7829)

Vulnerability from cvelistv5 – Published: 2026-07-01 03:33 – Updated: 2026-07-01 13:13
VLAI
Title
UltraVNC repeater authenticated out-of-bounds write in rule parser via oversized token
Summary
UltraVNC repeater through 1.8.2.2 contains a post-authentication out-of-bounds write in the allow/deny rule parser. In repeater/webgui/settings.c:225-272, after strncpy_s copies a rule token into temp1[rule1] (25-byte destination) or temp2/temp3 (16-byte destination), the code unconditionally writes a NUL terminator at temp1[rule1][len] = 0 without clamping len to the destination size. When an authenticated administrator saves a rule with a token length equal to or greater than the destination size, the NUL byte is written one or more bytes past the end of the stack-allocated array, corrupting adjacent stack data. An attacker who has obtained admin credentials (including via CVE-2026-7839 default password) can trigger this to gain code execution on the repeater host.
Severity
7.2 (High)
CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H
SSVC
Exploitation: none Automatable: no Technical Impact: total
CISA Coordinator (v2.0.3)
CWE
Assigner
References
URL Tags
https://uvnc.com/ vendor-advisory
https://github.com/ultravnc/UltraVNC product
Impacted products
Vendor Product Version
uvnc UltraVNC Affected: 0 , ≤ 1.8.2.2 (custom)
Create a notification for this product.
Credits
Arjun Basnet, Securin (arjun.basnet@securin.io)
Show details on NVD website
To clipboard 

{
  "containers": {
    "adp": [
      {
        "metrics": [
          {
            "other": {
              "content": {
                "id": "CVE-2026-7829",
                "options": [
                  {
                    "Exploitation": "none"
                  },
                  {
                    "Automatable": "no"
                  },
                  {
                    "Technical Impact": "total"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-07-01T13:13:45.463427Z",
                "version": "2.0.3"
              },
              "type": "ssvc"
            }
          }
        ],
        "providerMetadata": {
          "dateUpdated": "2026-07-01T13:13:52.948Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
        "title": "CISA ADP Vulnrichment"
      }
    ],
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "modules": [
            "repeater"
          ],
          "product": "UltraVNC",
          "vendor": "uvnc",
          "versions": [
            {
              "lessThanOrEqual": "1.8.2.2",
              "status": "affected",
              "version": "0",
              "versionType": "custom"
            }
          ]
        }
      ],
      "credits": [
        {
          "lang": "en",
          "type": "finder",
          "value": "Arjun Basnet, Securin (arjun.basnet@securin.io)"
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "UltraVNC repeater through 1.8.2.2 contains a post-authentication out-of-bounds write in the allow/deny rule parser. In repeater/webgui/settings.c:225-272, after strncpy_s copies a rule token into temp1[rule1] (25-byte destination) or temp2/temp3 (16-byte destination), the code unconditionally writes a NUL terminator at temp1[rule1][len] = 0 without clamping len to the destination size. When an authenticated administrator saves a rule with a token length equal to or greater than the destination size, the NUL byte is written one or more bytes past the end of the stack-allocated array, corrupting adjacent stack data. An attacker who has obtained admin credentials (including via CVE-2026-7839 default password) can trigger this to gain code execution on the repeater host."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "attackComplexity": "LOW",
            "attackVector": "NETWORK",
            "availabilityImpact": "HIGH",
            "baseScore": 7.2,
            "baseSeverity": "HIGH",
            "confidentialityImpact": "HIGH",
            "integrityImpact": "HIGH",
            "privilegesRequired": "HIGH",
            "scope": "UNCHANGED",
            "userInteraction": "NONE",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H",
            "version": "3.1"
          },
          "format": "CVSS",
          "scenarios": [
            {
              "lang": "en",
              "value": "GENERAL"
            }
          ]
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-787",
              "description": "Out-of-bounds Write",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-07-01T03:33:22.888Z",
        "orgId": "33c584b5-0579-4c06-b2a0-8d8329fcab9c",
        "shortName": "securin"
      },
      "references": [
        {
          "name": "UltraVNC project page",
          "tags": [
            "vendor-advisory"
          ],
          "url": "https://uvnc.com/"
        },
        {
          "name": "UltraVNC source repository",
          "tags": [
            "product"
          ],
          "url": "https://github.com/ultravnc/UltraVNC"
        }
      ],
      "source": {
        "advisory": "Securin Security Advisory \u2014 FINDING-007",
        "discovery": "EXTERNAL"
      },
      "timeline": [
        {
          "lang": "en",
          "time": "2026-06-02T00:00:00.000Z",
          "value": "Vulnerability discovered during security audit"
        },
        {
          "lang": "en",
          "time": "2026-06-17T00:00:00.000Z",
          "value": "Reported to vendor (coordinated disclosure)"
        },
        {
          "lang": "en",
          "time": "2026-09-15T00:00:00.000Z",
          "value": "Planned public disclosure (90-day window)"
        }
      ],
      "title": "UltraVNC repeater authenticated out-of-bounds write in rule parser via oversized token"
    }
  },
  "cveMetadata": {
    "assignerOrgId": "33c584b5-0579-4c06-b2a0-8d8329fcab9c",
    "assignerShortName": "securin",
    "cveId": "CVE-2026-7829",
    "datePublished": "2026-07-01T03:33:22.888Z",
    "dateReserved": "2026-05-05T03:40:57.359Z",
    "dateUpdated": "2026-07-01T13:13:52.948Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2",
  "vulnerability-lookup:meta": {
    "epss": {
      "cve": "CVE-2026-7829",
      "date": "2026-07-02",
      "epss": "0.00504",
      "percentile": "0.394"
    },
    "nvd": "{\"cve\":{\"id\":\"CVE-2026-7829\",\"sourceIdentifier\":\"33c584b5-0579-4c06-b2a0-8d8329fcab9c\",\"published\":\"2026-07-01T05:16:24.087\",\"lastModified\":\"2026-07-02T15:09:54.440\",\"vulnStatus\":\"Analyzed\",\"cveTags\":[],\"descriptions\":[{\"lang\":\"en\",\"value\":\"UltraVNC repeater through 1.8.2.2 contains a post-authentication out-of-bounds write in the allow/deny rule parser. In repeater/webgui/settings.c:225-272, after strncpy_s copies a rule token into temp1[rule1] (25-byte destination) or temp2/temp3 (16-byte destination), the code unconditionally writes a NUL terminator at temp1[rule1][len] = 0 without clamping len to the destination size. When an authenticated administrator saves a rule with a token length equal to or greater than the destination size, the NUL byte is written one or more bytes past the end of the stack-allocated array, corrupting adjacent stack data. An attacker who has obtained admin credentials (including via CVE-2026-7839 default password) can trigger this to gain code execution on the repeater host.\"}],\"affected\":[{\"source\":\"33c584b5-0579-4c06-b2a0-8d8329fcab9c\",\"affectedData\":[{\"vendor\":\"uvnc\",\"product\":\"UltraVNC\",\"defaultStatus\":\"unaffected\",\"modules\":[\"repeater\"],\"versions\":[{\"version\":\"0\",\"lessThanOrEqual\":\"1.8.2.2\",\"versionType\":\"custom\",\"status\":\"affected\"}]}]}],\"metrics\":{\"cvssMetricV31\":[{\"source\":\"33c584b5-0579-4c06-b2a0-8d8329fcab9c\",\"type\":\"Secondary\",\"cvssData\":{\"version\":\"3.1\",\"vectorString\":\"CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H\",\"baseScore\":7.2,\"baseSeverity\":\"HIGH\",\"attackVector\":\"NETWORK\",\"attackComplexity\":\"LOW\",\"privilegesRequired\":\"HIGH\",\"userInteraction\":\"NONE\",\"scope\":\"UNCHANGED\",\"confidentialityImpact\":\"HIGH\",\"integrityImpact\":\"HIGH\",\"availabilityImpact\":\"HIGH\"},\"exploitabilityScore\":1.2,\"impactScore\":5.9}],\"ssvcV203\":[{\"source\":\"134c704f-9b21-4f2e-91b3-4a467353bcc0\",\"ssvcData\":{\"timestamp\":\"2026-07-01T13:13:45.463427Z\",\"id\":\"CVE-2026-7829\",\"options\":[{\"exploitation\":\"none\"},{\"automatable\":\"no\"},{\"technicalImpact\":\"total\"}],\"role\":\"CISA Coordinator\",\"version\":\"2.0.3\"}}]},\"weaknesses\":[{\"source\":\"33c584b5-0579-4c06-b2a0-8d8329fcab9c\",\"type\":\"Secondary\",\"description\":[{\"lang\":\"en\",\"value\":\"CWE-787\"}]}],\"configurations\":[{\"nodes\":[{\"operator\":\"OR\",\"negate\":false,\"cpeMatch\":[{\"vulnerable\":true,\"criteria\":\"cpe:2.3:a:uvnc:ultravnc:*:*:*:*:*:*:*:*\",\"versionEndIncluding\":\"1.8.2.2\",\"matchCriteriaId\":\"593F7EC1-0922-4652-817A-7D57A0F1210D\"}]}]}],\"references\":[{\"url\":\"https://github.com/ultravnc/UltraVNC\",\"source\":\"33c584b5-0579-4c06-b2a0-8d8329fcab9c\",\"tags\":[\"Product\"]},{\"url\":\"https://uvnc.com/\",\"source\":\"33c584b5-0579-4c06-b2a0-8d8329fcab9c\",\"tags\":[\"Product\",\"Release Notes\"]}]}}",
    "vulnrichment": {
      "containers": "{\"adp\": [{\"title\": \"CISA ADP Vulnrichment\", \"metrics\": [{\"other\": {\"type\": \"ssvc\", \"content\": {\"id\": \"CVE-2026-7829\", \"role\": \"CISA Coordinator\", \"options\": [{\"Exploitation\": \"none\"}, {\"Automatable\": \"no\"}, {\"Technical Impact\": \"total\"}], \"version\": \"2.0.3\", \"timestamp\": \"2026-07-01T13:13:45.463427Z\"}}}], \"providerMetadata\": {\"orgId\": \"134c704f-9b21-4f2e-91b3-4a467353bcc0\", \"shortName\": \"CISA-ADP\", \"dateUpdated\": \"2026-07-01T13:13:49.716Z\"}}], \"cna\": {\"title\": \"UltraVNC repeater authenticated out-of-bounds write in rule parser via oversized token\", \"source\": {\"advisory\": \"Securin Security Advisory \\u2014 FINDING-007\", \"discovery\": \"EXTERNAL\"}, \"credits\": [{\"lang\": \"en\", \"type\": \"finder\", \"value\": \"Arjun Basnet, Securin (arjun.basnet@securin.io)\"}], \"metrics\": [{\"format\": \"CVSS\", \"cvssV3_1\": {\"scope\": \"UNCHANGED\", \"version\": \"3.1\", \"baseScore\": 7.2, \"attackVector\": \"NETWORK\", \"baseSeverity\": \"HIGH\", \"vectorString\": \"CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H\", \"integrityImpact\": \"HIGH\", \"userInteraction\": \"NONE\", \"attackComplexity\": \"LOW\", \"availabilityImpact\": \"HIGH\", \"privilegesRequired\": \"HIGH\", \"confidentialityImpact\": \"HIGH\"}, \"scenarios\": [{\"lang\": \"en\", \"value\": \"GENERAL\"}]}], \"affected\": [{\"vendor\": \"uvnc\", \"modules\": [\"repeater\"], \"product\": \"UltraVNC\", \"versions\": [{\"status\": \"affected\", \"version\": \"0\", \"versionType\": \"custom\", \"lessThanOrEqual\": \"1.8.2.2\"}], \"defaultStatus\": \"unaffected\"}], \"timeline\": [{\"lang\": \"en\", \"time\": \"2026-06-02T00:00:00.000Z\", \"value\": \"Vulnerability discovered during security audit\"}, {\"lang\": \"en\", \"time\": \"2026-06-17T00:00:00.000Z\", \"value\": \"Reported to vendor (coordinated disclosure)\"}, {\"lang\": \"en\", \"time\": \"2026-09-15T00:00:00.000Z\", \"value\": \"Planned public disclosure (90-day window)\"}], \"references\": [{\"url\": \"https://uvnc.com/\", \"name\": \"UltraVNC project page\", \"tags\": [\"vendor-advisory\"]}, {\"url\": \"https://github.com/ultravnc/UltraVNC\", \"name\": \"UltraVNC source repository\", \"tags\": [\"product\"]}], \"descriptions\": [{\"lang\": \"en\", \"value\": \"UltraVNC repeater through 1.8.2.2 contains a post-authentication out-of-bounds write in the allow/deny rule parser. In repeater/webgui/settings.c:225-272, after strncpy_s copies a rule token into temp1[rule1] (25-byte destination) or temp2/temp3 (16-byte destination), the code unconditionally writes a NUL terminator at temp1[rule1][len] = 0 without clamping len to the destination size. When an authenticated administrator saves a rule with a token length equal to or greater than the destination size, the NUL byte is written one or more bytes past the end of the stack-allocated array, corrupting adjacent stack data. An attacker who has obtained admin credentials (including via CVE-2026-7839 default password) can trigger this to gain code execution on the repeater host.\"}], \"problemTypes\": [{\"descriptions\": [{\"lang\": \"en\", \"type\": \"CWE\", \"cweId\": \"CWE-787\", \"description\": \"Out-of-bounds Write\"}]}], \"providerMetadata\": {\"orgId\": \"33c584b5-0579-4c06-b2a0-8d8329fcab9c\", \"shortName\": \"securin\", \"dateUpdated\": \"2026-07-01T03:33:22.888Z\"}}}",
      "cveMetadata": "{\"cveId\": \"CVE-2026-7829\", \"state\": \"PUBLISHED\", \"dateUpdated\": \"2026-07-01T13:13:52.948Z\", \"dateReserved\": \"2026-05-05T03:40:57.359Z\", \"assignerOrgId\": \"33c584b5-0579-4c06-b2a0-8d8329fcab9c\", \"datePublished\": \"2026-07-01T03:33:22.888Z\", \"assignerShortName\": \"securin\"}",
      "dataType": "CVE_RECORD",
      "dataVersion": "5.2"
    }
  }
}


Log in or create an account to share your comment.




Tags
Taxonomy of the tags.





Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

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.


Detection rules are retrieved from Rulezet.