CVE-2026-53165 iomap: avoid potential null folio->mapping deref during error reporting

What is CVE-2026-53165?

CVE-2026-53165 is a high-severity vulnerability in Linux kernel, published on 25 Jun 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

Official description

In the Linux kernel, the following vulnerability has been resolved:

iomap: avoid potential null folio->mapping deref during error reporting

When a buffered read fails, iomap_finish_folio_read() reports the error with fserror_report_io(folio->mapping->host, ...). This is called after ifs->read_bytes_pending has been decremented by the bytes attempted to be read.

For a folio split across multiple read completions, the folio is only guaranteed to stay locked while read_bytes_pending > 0. Once iomap_finish_folio_read() decrements read_bytes_pending, another in-flight read can complete and end the read on the folio, which unlocks it. This allows truncate logic to run and detach the folio (set folio->mapping to NULL). The error reporting path then can dereference a NULL folio->mapping. As reported by Sam Sun, this is the race that can occur:

CPU0: failed completion CPU1: final completion CPU2: truncate ----------------------- ---------------------- -------------- read_bytes_pending -= len finished = false /* preempted before fserror_report_io() */ read_bytes_pending -= len finished = true folio_end_read() truncate clears folio->mapping fserror_report_io( folio->mapping->host, ...) ^ NULL deref

Fix this by reporting the error first before decrementing ifs->read_bytes_pending.

Weakness: CWE-476

Which versions are affected by CVE-2026-53165?

It affects 1 product.

Products include Linux kernel.

How do I fix CVE-2026-53165?

Apply the vendor's patch.

Is CVE-2026-53165 being exploited?

There is no known exploitation of CVE-2026-53165 in the wild and no public exploit code.

Other vulnerabilities in Linux kernel

• CVE-2026-53266 Linux Kernel Out-of-Bounds Write Exploited High 8.8
• CVE-2013-6282 Linux Kernel Improper Input Validation Exploited High 8.8
• CVE-2022-0185 Linux Kernel Heap-Based Buffer Overflow Exploited High 8.4
• CVE-2013-2094 Linux Kernel Privilege Escalation Exploited High 8.4
• CVE-2026-53362 Linux Kernel Unspecified Exploited High 7.8

All Linux kernel vulnerabilities

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as DEBIAN-CVE-2026-53165, GHSA-f5cm-4mmf-92c9, ROOT-OS-UBUNTU-2204-CVE-2026-53165, ROOT-OS-UBUNTU-2404-CVE-2026-53165, UBUNTU-CVE-2026-53165.