Cloudanix VulnDB

CVE-2026-98879

None

CVSS

—

EPSS

0.2%

Published

Oct 23, 2026

CISA due date

—

Cloudanix analysis

Schedule a fix SSVC: Track

A flaw when reading certain disk image files can cause the computer to crash unexpectedly.

Exploitation
Local Privilege
Attacker needs
Local User
Complexity
Low
Impact
Denial Of Service
Component
OS kernel
Class
Improper Input Validation
Remediation
Upgrade
Effort
Medium
Patch risk
Low

What it actually does

Failure to handle set_blocksize errors in the isofs filesystem driver triggers a kernel BUG_ON assertion in folio_set_bh when mounting filesystems with block sizes exceeding page size, causing a crash on the first __bread_gfp call.

Why it matters to the business

Systems may experience unexpected kernel panics and reboots when accessing certain disk image files, disrupting availability for users or services that mount external media. Low EPSS and absence from KEV indicate limited active exploitation risk two days after publication.

How an attack unfolds

An attacker supplies a crafted ISO9660 image with block size larger than PAGE_SIZE. When the victim attempts to mount it, isofs proceeds without validating set_blocksize success, hitting the BUG_ON and panicking the kernel.

How to fix it

Apply the upstream Linux kernel patch that adds proper set_blocksize failure handling in isofs. Rebuild and deploy updated kernels to affected systems; test mounts of varied ISO images post-update.

How to confirm the fix worked

Confirm the fix is present by reviewing kernel source for isofs set_blocksize error paths or by attempting to mount test ISOs with block sizes > PAGE_SIZE without observing BUG_ON.

Typical attack path

  1. Craft or obtain ISO image with block size exceeding PAGE_SIZE
  2. Induce target system to mount the image via local or remote means
  3. Mount operation invokes folio_set_bh and triggers BUG_ON

How to detect it

Inspect kernel logs and dmesg output for BUG_ON messages referencing folio_set_bh or isofs during mount attempts; correlate with recent ISO mount activity.

What your security team should do

  • Expedite kernel updates on systems that mount untrusted ISO images
  • Restrict unprivileged mount operations where feasible
  • Review kernel logs for isofs-related panics as part of routine monitoring

The record

In the Linux kernel, the following vulnerability has been resolved: isofs: handle set_blocksize failures isofs uses buffer_heads, which don't handle block size > PAGE_SIZE well. Without this, mounting we will hit the BUG_ON(offset >= folio_size(folio)); in folio_set_bh on the first __bread_gfp call.

Affected packages

Ecosystem Package Introduced Fixed