CVE-2026-89778: Linux kernel · isofs: fix out-of-bounds page array access on empty zisofs block
Affects Linux kernelSource GCVE Database
Not known to be exploited · CVSS 9.8 Critical.
Data as of 26 Oct 2026, 14:05 UTC
- EPSS
- 0.6% chance of exploitation in 30 days – higher than 52% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:HExploitation evidence
Disclosed: evidence found.
CVE published 16 Sep 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.
What to do
Affected software
| Product | Affected | Fixed in |
|---|---|---|
Ubuntu 26.04 LTSlinuxpkg:deb/ubuntu/linux?arch=source&distro=resoluteOther threats | Affected
| Fixed in– |
Ubuntu 26.04 LTSlinux-awspkg:deb/ubuntu/linux-aws?arch=source&distro=resoluteOther threats | Affected
| Fixed in– |
Ubuntu 26.04 LTSlinux-azurepkg:deb/ubuntu/linux-azure?arch=source&distro=resoluteOther threats | Affected
| Fixed in– |
Ubuntu 26.04 LTSlinux-azure-fdepkg:deb/ubuntu/linux-azure-fde?arch=source&distro=resoluteOther threats | Affected
| Fixed in– |
Ubuntu 26.04 LTSlinux-gcppkg:deb/ubuntu/linux-gcp?arch=source&distro=resoluteOther threats | Affected
| Fixed in– |
Ubuntu 26.04 LTSlinux-gkepkg:deb/ubuntu/linux-gke?arch=source&distro=resoluteOther threats | Affected
| Fixed in– |
Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.
AI-suggested
A fix has been implemented in the Linux kernel to correct the byte count handling in zisofs_uncompress_block() and prevent out-of-bounds access. Users should update to a Linux kernel version that includes this fix. Since this is a kernel vulnerability, applying the official kernel patch or upgrading to a fixed kernel release is the recommended remediation.
Description
A vulnerability in the Linux kernel's isofs filesystem driver allows out-of-bounds page array access when reading empty zisofs blocks under certain conditions. This occurs due to incorrect handling of the byte count relative to the page offset in zisofs_uncompress_block(), leading to an out-of-bounds read in zisofs_fill_pages(). The flaw can be triggered by reading a specially crafted compressed file on a mounted ISO9660 image with a manipulated block size. This issue has been resolved in the Linux kernel.
References
- ubuntu.com/security/CVE-2026-89778 (opens in a new tab)
- cve.org/CVERecord?id=CVE-2026-89778 (opens in a new tab)
- git.kernel.org/linus/68d4d3e78150c7ed7d1195af63ad1e6ace30c661 (opens in a new tab)
- git.kernel.org/stable/c/68d4d3e78150c7ed7d1195af63ad1e6ace30c661 (opens in a new tab)
- git.kernel.org/stable/c/85904076cece72ee3194646ad7ac8e6659d999aa (opens in a new tab)
- git.kernel.org/stable/c/8b994ac5778a725982fd6a8a3afcaa068d4a93e3 (opens in a new tab)
- git.kernel.org/stable/c/9c6eace8d07e90f038c89eb3b756d65a7e259d48 (opens in a new tab)
- git.kernel.org/stable/c/ad3249cdf9d4ba34bb8b1ff3956a4020fdfb5b0a (opens in a new tab)
- git.kernel.org/stable/c/cd616aa0449a772a6956abf03358f0ff31720580 (opens in a new tab)
- git.kernel.org/stable/c/f03425dcbe04aec3c27b9917e97d7d23a2908dda (opens in a new tab)