Vulnerability-Lookup

GHSA-R575-8HW6-VFQ3

Vulnerability from github – Published: 2026-10-08 15:32 – Updated: 2026-10-08 15:32

Details

An out-of-bounds read vulnerability in the ZRLE decoder of GlavSoft TightVNC Viewer for Windows before 2.8.88 allows a malicious or compromised VNC server to read heap memory beyond the palette allocation and crash the viewer by sending ZRLE-encoded tiles whose palette indices exceed the declared palette size. readPaletteRleTile() and readPackedPaletteTile() use the attacker-supplied index to look up colours without validating it against the palette size; out-of-bounds heap data is copied into the framebuffer (garbled display) or the read faults, terminating the viewer.

Severity

7.1 (High)


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

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JSON

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{
  "affected": [],
  "aliases": [
    "CVE-2026-107611"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-125"
    ],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-10-08T14:16:49Z",
    "severity": "HIGH"
  },
  "details": "An out-of-bounds read vulnerability in the ZRLE decoder of GlavSoft TightVNC Viewer for Windows before 2.8.88 allows a malicious or compromised VNC server to read heap memory beyond the palette allocation and crash the viewer by sending ZRLE-encoded tiles whose palette indices exceed the declared palette size. readPaletteRleTile() and readPackedPaletteTile() use the attacker-supplied index to look up colours without validating it against the palette size; out-of-bounds heap data is copied into the framebuffer (garbled display) or the read faults, terminating the viewer.",
  "id": "GHSA-r575-8hw6-vfq3",
  "modified": "2026-10-08T15:32:58Z",
  "published": "2026-10-08T15:32:58Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-107611"
    },
    {
      "type": "WEB",
      "url": "https://sourceforge.net/p/vnc-tight/bugs/1657"
    },
    {
      "type": "WEB",
      "url": "https://www.tightvnc.com/whatsnew.php"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:H",
      "type": "CVSS_V3"
    }
  ]
}

CVE-2026-107611 (GCVE-0-2026-107611)

Vulnerability from cvelistv5 – Published: 2026-10-08 13:39 – Updated: 2026-10-08 14:03

Title

Out-of-bounds read in TightVNC Viewer ZRLE palette decoding

Summary

Severity

7.1 (High)


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

SSVC

Exploitation: none Automatable: no Technical Impact: partial

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-10-08 14:02 UTC

CWE

CWE-125 - Out-of-bounds Read

Assigner

securin CNA under the mitre root

CNA scorecard B 80/100 over 70 records in the last 180 days details

References

2 references

URL	Tags
https://sourceforge.net/p/vnc-tight/bugs/1657/	issue-tracking
https://www.tightvnc.com/whatsnew.php	release-notespatch

Impacted products

1 product

Vendor	Product	Version
GlavSoft	TightVNC	Affected: 0 , < 2.8.88 (custom)

Credits

Arjun Basnet from Securin

Show details on NVD website

JSON

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{
  "containers": {
    "adp": [
      {
        "metrics": [
          {
            "other": {
              "content": {
                "id": "CVE-2026-107611",
                "options": [
                  {
                    "Exploitation": "none"
                  },
                  {
                    "Automatable": "no"
                  },
                  {
                    "Technical Impact": "partial"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-10-08T14:02:42.563819Z",
                "version": "2.0.3"
              },
              "type": "ssvc"
            }
          }
        ],
        "providerMetadata": {
          "dateUpdated": "2026-10-08T14:03:01.404Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
        "title": "CISA ADP Vulnrichment"
      }
    ],
    "cna": {
      "affected": [
        {
          "defaultStatus": "unaffected",
          "modules": [
            "TightVNC Viewer (ZRLE decoder)"
          ],
          "platforms": [
            "Windows"
          ],
          "product": "TightVNC",
          "programFiles": [
            "ZrleDecoder.cpp"
          ],
          "programRoutines": [
            {
              "name": "readPaletteRleTile()"
            },
            {
              "name": "readPackedPaletteTile()"
            }
          ],
          "vendor": "GlavSoft",
          "versions": [
            {
              "lessThan": "2.8.88",
              "status": "affected",
              "version": "0",
              "versionType": "custom"
            }
          ]
        }
      ],
      "credits": [
        {
          "lang": "en",
          "type": "finder",
          "value": "Arjun Basnet from Securin"
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "An out-of-bounds read vulnerability in the ZRLE decoder of GlavSoft TightVNC Viewer for Windows before 2.8.88 allows a malicious or compromised VNC server to read heap memory beyond the palette allocation and crash the viewer by sending ZRLE-encoded tiles whose palette indices exceed the declared palette size. readPaletteRleTile() and readPackedPaletteTile() use the attacker-supplied index to look up colours without validating it against the palette size; out-of-bounds heap data is copied into the framebuffer (garbled display) or the read faults, terminating the viewer."
        }
      ],
      "impacts": [
        {
          "capecId": "CAPEC-540",
          "descriptions": [
            {
              "lang": "en",
              "value": "CAPEC-540 Overread Buffers"
            }
          ]
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "baseScore": 7.1,
            "baseSeverity": "HIGH",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:N/A:H",
            "version": "3.1"
          },
          "format": "CVSS",
          "scenarios": [
            {
              "lang": "en",
              "value": "GENERAL"
            }
          ]
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-125",
              "description": "CWE-125 Out-of-bounds Read",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-10-08T13:39:48.883Z",
        "orgId": "33c584b5-0579-4c06-b2a0-8d8329fcab9c",
        "shortName": "securin"
      },
      "references": [
        {
          "name": "TightVNC bug #1657",
          "tags": [
            "issue-tracking"
          ],
          "url": "https://sourceforge.net/p/vnc-tight/bugs/1657/"
        },
        {
          "name": "TightVNC release notes (2.8.88)",
          "tags": [
            "release-notes",
            "patch"
          ],
          "url": "https://www.tightvnc.com/whatsnew.php"
        }
      ],
      "solutions": [
        {
          "lang": "en",
          "value": "Upgrade TightVNC for Windows to version 2.8.88 or later."
        }
      ],
      "source": {
        "discovery": "EXTERNAL"
      },
      "timeline": [
        {
          "lang": "en",
          "time": "2026-05-30T00:00:00.000Z",
          "value": "Reported to GlavSoft"
        },
        {
          "lang": "en",
          "time": "2026-06-02T00:00:00.000Z",
          "value": "Vendor acknowledged"
        },
        {
          "lang": "en",
          "time": "2026-06-19T00:00:00.000Z",
          "value": "TightVNC 2.8.88 released with fix"
        }
      ],
      "title": "Out-of-bounds read in TightVNC Viewer ZRLE palette decoding",
      "workarounds": [
        {
          "lang": "en",
          "value": "Connect only to trusted VNC servers until the viewer is upgraded."
        }
      ]
    }
  },
  "cveMetadata": {
    "assignerOrgId": "33c584b5-0579-4c06-b2a0-8d8329fcab9c",
    "assignerShortName": "securin",
    "cveId": "CVE-2026-107611",
    "datePublished": "2026-10-08T13:39:48.883Z",
    "dateReserved": "2026-10-08T13:23:07.677Z",
    "dateUpdated": "2026-10-08T14:03:01.404Z",
    "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.
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Action not permitted

GHSA-R575-8HW6-VFQ3

CVE-2026-107611 (GCVE-0-2026-107611)

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