UBUNTU-CVE-2026-33023

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Source
https://ubuntu.com/security/CVE-2026-33023
Import Source
https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-33023.json
JSON Data
https://api.test.osv.dev/v1/vulns/UBUNTU-CVE-2026-33023
Upstream
  • CVE-2026-33023
Published
2026-04-14T23:16:00Z
Modified
2026-04-16T11:05:00.893787Z
Severity
  • 7.8 (High) CVSS_V3 - CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H CVSS Calculator
  • Ubuntu - medium
Summary
[none]
Details

libsixel is a SIXEL encoder/decoder implementation derived from kmiya's sixel. In versions 1.8.7 and prior, when built with the --with-gdk-pixbuf2 option, a use-after-free vulnerability exists in loadwithgdkpixbuf() in loader.c. The cleanup path manually frees the sixelframet object and its internal buffers without consulting the reference count, even though the object was created via the refcounted constructor sixelframenew() and exposed to the public callback. A callback that calls sixelframeref(frame) to retain a logically valid reference will hold a dangling pointer after sixelhelperloadimagefile() returns, and any subsequent access to the frame or its fields triggers a use-after-free confirmed by AddressSanitizer. The root cause is a consistency failure between two cleanup strategies in the same codebase: sixelframeunref() is used in loadwithbuiltin() but raw free() is used in loadwithgdkpixbuf(). An attacker supplying a crafted image to any application built against libsixel with gdk-pixbuf2 support can trigger this reliably, potentially leading to information disclosure, memory corruption, or code execution. This issue has been fixed in version 1.8.7-r1.

References

Affected packages

Ubuntu:16.04:LTS
libsixel

Package

Name
libsixel
Purl
pkg:deb/ubuntu/libsixel@1.5.2-2?arch=source&distro=xenial

Affected ranges

Type
ECOSYSTEM
Events
Introduced
0Unknown introduced version / All previous versions are affected

Affected versions

1.*
1.4.2-1
1.5.2-2

Ecosystem specific 

{
    "binaries": [
        {
            "binary_version": "1.5.2-2",
            "binary_name": "libsixel-bin"
        },
        {
            "binary_version": "1.5.2-2",
            "binary_name": "libsixel-dev"
        },
        {
            "binary_version": "1.5.2-2",
            "binary_name": "libsixel1"
        }
    ]
}

Database specific

source 
"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-33023.json"
Ubuntu:18.04:LTS
libsixel

Package

Name
libsixel
Purl
pkg:deb/ubuntu/libsixel@1.7.3-1?arch=source&distro=bionic

Affected ranges

Type
ECOSYSTEM
Events
Introduced
0Unknown introduced version / All previous versions are affected

Affected versions

1.*
1.5.2-2
1.7.3-1

Ecosystem specific 

{
    "binaries": [
        {
            "binary_version": "1.7.3-1",
            "binary_name": "libsixel-bin"
        },
        {
            "binary_version": "1.7.3-1",
            "binary_name": "libsixel-dev"
        },
        {
            "binary_version": "1.7.3-1",
            "binary_name": "libsixel-examples"
        },
        {
            "binary_version": "1.7.3-1",
            "binary_name": "libsixel1"
        }
    ]
}

Database specific

source 
"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-33023.json"
Ubuntu:20.04:LTS
libsixel

Package

Name
libsixel
Purl
pkg:deb/ubuntu/libsixel@1.8.2-2.1?arch=source&distro=focal

Affected ranges

Type
ECOSYSTEM
Events
Introduced
0Unknown introduced version / All previous versions are affected

Affected versions

1.*
1.8.2-1
1.8.2-2.1

Ecosystem specific 

{
    "binaries": [
        {
            "binary_version": "1.8.2-2.1",
            "binary_name": "libsixel-bin"
        },
        {
            "binary_version": "1.8.2-2.1",
            "binary_name": "libsixel-dev"
        },
        {
            "binary_version": "1.8.2-2.1",
            "binary_name": "libsixel-examples"
        },
        {
            "binary_version": "1.8.2-2.1",
            "binary_name": "libsixel1"
        }
    ]
}

Database specific

source 
"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-33023.json"
Ubuntu:22.04:LTS
libsixel

Package

Name
libsixel
Purl
pkg:deb/ubuntu/libsixel@1.10.3-3?arch=source&distro=jammy

Affected ranges

Type
ECOSYSTEM
Events
Introduced
0Unknown introduced version / All previous versions are affected

Affected versions

1.*
1.8.6-2
1.10.3-2
1.10.3-3

Ecosystem specific 

{
    "binaries": [
        {
            "binary_version": "1.10.3-3",
            "binary_name": "libsixel-bin"
        },
        {
            "binary_version": "1.10.3-3",
            "binary_name": "libsixel-dev"
        },
        {
            "binary_version": "1.10.3-3",
            "binary_name": "libsixel-examples"
        },
        {
            "binary_version": "1.10.3-3",
            "binary_name": "libsixel1"
        }
    ]
}

Database specific

source 
"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-33023.json"
Ubuntu:24.04:LTS
libsixel

Package

Name
libsixel
Purl
pkg:deb/ubuntu/libsixel@1.10.3-3build1?arch=source&distro=noble

Affected ranges

Type
ECOSYSTEM
Events
Introduced
0Unknown introduced version / All previous versions are affected

Affected versions

1.*
1.10.3-3
1.10.3-3build1

Ecosystem specific 

{
    "binaries": [
        {
            "binary_version": "1.10.3-3build1",
            "binary_name": "libsixel-bin"
        },
        {
            "binary_version": "1.10.3-3build1",
            "binary_name": "libsixel-dev"
        },
        {
            "binary_version": "1.10.3-3build1",
            "binary_name": "libsixel-examples"
        },
        {
            "binary_version": "1.10.3-3build1",
            "binary_name": "libsixel1"
        }
    ]
}

Database specific

source 
"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-33023.json"
Ubuntu:25.10
libsixel

Package

Name
libsixel
Purl
pkg:deb/ubuntu/libsixel@1.10.5-1?arch=source&distro=questing

Affected ranges

Type
ECOSYSTEM
Events
Introduced
0Unknown introduced version / All previous versions are affected

Affected versions

1.*
1.10.5-1

Ecosystem specific 

{
    "binaries": [
        {
            "binary_version": "1.10.5-1",
            "binary_name": "libsixel-bin"
        },
        {
            "binary_version": "1.10.5-1",
            "binary_name": "libsixel-dev"
        },
        {
            "binary_version": "1.10.5-1",
            "binary_name": "libsixel-examples"
        },
        {
            "binary_version": "1.10.5-1",
            "binary_name": "libsixel1"
        }
    ]
}

Database specific

source 
"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-33023.json"