UBUNTU-CVE-2026-61626

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Source
https://ubuntu.com/security/CVE-2026-61626
Import Source
https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-61626.json
JSON Data
https://api.osv.dev/v1/vulns/UBUNTU-CVE-2026-61626
Upstream
Downstream
Related
Published
2026-07-14T00:00:00Z
Modified
2026-11-05T11:46:35Z
Severity
  • 7.3 (High) CVSS_V4 - CVSS:4.0/AV:L/AC:H/AT:N/PR:N/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N CVSS Calculator
  • Ubuntu - medium
Summary
[none]
Details

libass is a portable subtitle renderer for the ASS/SSA (Advanced Substation Alpha/Substation Alpha) subtitle format. From 0.17.4 until 0.17.5, libass event pruning does not guard negative Matroska ReadOrder values, allowing an attacker to clear arbitrarily many bits to zero at attacker-controlled positions near the NULL pointer. Exploitation requires a malicious Matroska stream loaded through ass_process_chunk, enabled read-order checking, and later pruning of the malicious events. Read-order checking is enabled by default unless ass_set_check_readorder is called with zero; pruning must occur explicitly through ass_prune_events or through automatic pruning previously enabled with ass_configure_prune. On common systems with arithmetic right shift, 32-bit int values, the upper address region reserved to the kernel, and matching binary/kernel architecture, the expected consequence is denial of service. More extensive exploitation on uncommon systems is theoretical and strongly constrained by the target addresses, bit-clearing-only mutation, and ASLR. This issue is fixed in version 0.17.5.

References

Affected packages

Ubuntu:Pro:26.04:LTS / libass

Package

Name
libass
Purl
pkg:deb/ubuntu/libass?arch=source&distro=esm-apps%2Fresolute

Affected ranges

Type
ECOSYSTEM
Events
Introduced
0 Unknown introduced version / All previous versions are affected
Fixed
1:0.17.4-2ubuntu0.1~esm1

Affected versions

1:0.*
1:0.17.3-1
1:0.17.4-2

Ecosystem specific 

{
    "availability": "Available with Ubuntu Pro: https://ubuntu.com/pro",
    "binaries": [
        {
            "binary_name": "libass9",
            "binary_version": "1:0.17.4-2ubuntu0.1~esm1"
        }
    ]
}

Database specific

source 
"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-61626.json"