CVE-2026-44988

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Source
https://cve.org/CVERecord?id=CVE-2026-44988
Import Source
https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-44988.json
JSON Data
https://api.osv.dev/v1/vulns/CVE-2026-44988
Aliases
  • GHSA-jcc5-8wj4-7c58
Downstream
Related
Published
2026-05-27T14:26:50.063Z
Modified
2026-07-15T17:34:34.489297Z
Severity
  • 8.8 (High) CVSS_V3 - CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H CVSS Calculator
Summary
LibVNCClient Tight Gradient decoding allows malicious server-triggered heap/stack OOB writes
Details

LibVNCClient is a library for easy implementation of a VNC client. In 0.9.15 and earlier, LibVNCClient's Tight encoding decoder uses fixed-size 2048-pixel scratch buffers for the Gradient filter, but it does not reject Tight rectangles whose width is larger than 2048 pixels. A malicious VNC server can send a crafted FramebufferUpdate rectangle using Tight encoding with NoZlib | ExplicitFilter and the Gradient filter. When a LibVNCClient-based client connects, the client processes the server-controlled rectangle width and writes beyond fixed-size Gradient buffers. This vulnerability is fixed with commit 5b270544b85233668b98161323297d418a8f5fd1.

Database specific 
{
    "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/44xxx/CVE-2026-44988.json",
    "cwe_ids": [
        "CWE-787"
    ],
    "cna_assigner": "GitHub_M"
}
References

Affected packages

Git / github.com/libvnc/libvncserver

Affected ranges

Type
GIT
Repo
https://github.com/libvnc/libvncserver
Events
Introduced
0 Unknown introduced commit / All previous commits are affected
Fixed
5b270544b85233668b98161323297d418a8f5fd1
Database specific 
{
    "extracted_events": [
        {
            "introduced": "0"
        },
        {
            "last_affected": "0.9.15"
        }
    ],
    "source": [
        "AFFECTED_FIELD",
        "REFERENCES"
    ]
}

Affected versions

LibVNCServer-0.*
LibVNCServer-0.9.10
LibVNCServer-0.9.11
LibVNCServer-0.9.12
LibVNCServer-0.9.13
LibVNCServer-0.9.14
LibVNCServer-0.9.15
LibVNCServer-0.9.8
LibVNCServer-0.9.9
Other
X11VNC_0_9_10
X11VNC_0_9_11
X11VNC_0_9_12
X11VNC_0_9_7
X11VNC_0_9_8
X11VNC_0_9_9
X11VNC_REL_0_9_4
X11VNC_REL_0_9_5
X11VNC_REL_0_9_6

Database specific

vanir_signatures 
[
    {
        "source": "https://github.com/libvnc/libvncserver/commit/5b270544b85233668b98161323297d418a8f5fd1",
        "deprecated": false,
        "signature_version": "v1",
        "digest": {
            "threshold": 0.9,
            "line_hashes": [
                "284112818668429985556250801126026456947",
                "146545894552328875471240250838610427439",
                "97822547301251185393985983941095869406",
                "298640970006803772311626728931039709666",
                "107040941370273155494797315645181744864",
                "145015383660600675083683478284247979767",
                "25480604597800297874487350170401835033"
            ]
        },
        "id": "CVE-2026-44988-2da6fcd1",
        "signature_type": "Line",
        "target": {
            "file": "include/rfb/rfbclient.h"
        }
    },
    {
        "source": "https://github.com/libvnc/libvncserver/commit/5b270544b85233668b98161323297d418a8f5fd1",
        "deprecated": false,
        "signature_version": "v1",
        "digest": {
            "function_hash": "243790435544429802424662206256558146553",
            "length": 1725.0
        },
        "id": "CVE-2026-44988-586d4fe3",
        "signature_type": "Function",
        "target": {
            "function": "FilterGradientBPP",
            "file": "src/libvncclient/tight.c"
        }
    },
    {
        "source": "https://github.com/libvnc/libvncserver/commit/5b270544b85233668b98161323297d418a8f5fd1",
        "deprecated": false,
        "signature_version": "v1",
        "digest": {
            "function_hash": "136204925171635408656217793287536555863",
            "length": 1212.0
        },
        "id": "CVE-2026-44988-6f93eb67",
        "signature_type": "Function",
        "target": {
            "function": "FilterGradient24",
            "file": "src/libvncclient/tight.c"
        }
    },
    {
        "source": "https://github.com/libvnc/libvncserver/commit/5b270544b85233668b98161323297d418a8f5fd1",
        "deprecated": false,
        "signature_version": "v1",
        "digest": {
            "function_hash": "308701212265011551369703570143399261208",
            "length": 4896.0
        },
        "id": "CVE-2026-44988-c2936c3d",
        "signature_type": "Function",
        "target": {
            "function": "HandleTightBPP",
            "file": "src/libvncclient/tight.c"
        }
    },
    {
        "source": "https://github.com/libvnc/libvncserver/commit/5b270544b85233668b98161323297d418a8f5fd1",
        "deprecated": false,
        "signature_version": "v1",
        "digest": {
            "threshold": 0.9,
            "line_hashes": [
                "928713364510983443011889069010387255",
                "125597362769918731336038997978203344292",
                "197029662172189727370869638080297154345",
                "131601997495272501374791808319565048851",
                "97287441679176143791124439911402995516",
                "45318158746677699697250290293611924448",
                "264892418141108533868932853703503574696",
                "143103705549547974506781061840419418289",
                "151629486138823699008590877938019170270",
                "130318485263964665546477862415709591453",
                "310067960931031303696407117321227591395",
                "317676275598388611502092189619460955782",
                "273401502033046250098606062202721216441"
            ]
        },
        "id": "CVE-2026-44988-f0ee344d",
        "signature_type": "Line",
        "target": {
            "file": "src/libvncclient/tight.c"
        }
    }
]
vanir_signatures_modified 
"2026-07-15T17:34:34Z"
source 
"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-44988.json"