---
id: CVE-2026-112007
title: Schism Tracker through 20260524 Heap Out-of-Bounds Write via ULT Loader
summary: >-
  Schism Tracker through 20260524 contains a heap out-of-bounds write
  vulnerability in fmt_ult_load_song() in fmt/ult.c that fails to clamp the
  one-byte sample count to MAX_SAMPLES. Attackers can supply a crafted .ult
  module that overwrite…
severity: medium
cvss: 6.1
cvssVector: 'CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:H'
cvssSource: cna
cwe:
  - CWE-787
vendor: schismtracker
product: Schism Tracker
affected:
  - schism_tracker <= 20260524
published: '2026-10-18'
updated: '2026-10-18'
sourceUpdated: '2026-10-18T11:38:30.590Z'
source: CVEORG
sourceUrl: 'https://www.cve.org/CVERecord?id=CVE-2026-112007'
references:
  - url: 'https://hackmd.io/@haindpwn/schismtracker-ult-sample-count-oob-write'
  - url: >-
      https://github.com/schismtracker/schismtracker/blob/74215ae300b555928332e03152dfcdc898f96ca6/fmt/ult.c#L319-L330
  - url: 'https://github.com/schismtracker/schismtracker'
  - url: >-
      https://www.vulncheck.com/advisories/schism-tracker-through-20260524-heap-out-of-bounds-write-via-ult-loader
    label: >-
      VulnCheck Advisory: Schism Tracker through 20260524 Heap Out-of-Bounds
      Write via ULT Loader
tags:
  - cve.org
ingestedAt: '2026-10-18T11:40:26.623Z'
---

## Overview

Schism Tracker through 20260524 contains a heap out-of-bounds write vulnerability in fmt_ult_load_song() in fmt/ult.c that fails to clamp the one-byte sample count to MAX_SAMPLES. Attackers can supply a crafted .ult module that overwrites the instruments pointer array, causing csf_destroy() to free attacker-chosen pointers and crash the application.

## Affected

- `schism_tracker <= 20260524`

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.