CVE-2026-98636: Linux kernel · squashfs: Add dictionary size range check to prevent shift-out-of-bounds
Affects Linux kernelSource GCVE Database
Not known to be exploited · CVSS 0.0 Medium.
Data as of 28 Oct 2026, 01:28 UTC
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:N/SC:N/SI:N/SA:NExploitation evidence
Disclosed: evidence found.
CVE published 18 Oct 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.
Description
In the Linux kernel, the following vulnerability has been resolved: squashfs: Add dictionary size range check to prevent shift-out-of-bounds When an abnormal SquashFS image (COMP_OPTS flag is 1 but dictionary size is 0) is mounted, and performs shift operations using dictionarysize, the shift exponent is -1, causing a shift-out-of-bounds. Detail as below: squashfs_comp_opts(msblk, buffer, length) squashfs_xz_comp_opts() if (comp_opts) n = ffs(opts->dict_size) - 1;<----opts->dict_size=0, n=-1 if (opts->dict_size != (1 << n) && opts->dict_size != (1 << n) + (1 << (n + 1))) <----shift-out-of-bounds Fix it by adding a dictionary size range check before the shift operation.
References
- ubuntu.com/security/CVE-2026-98636 (opens in a new tab)
- cve.org/CVERecord?id=CVE-2026-98636 (opens in a new tab)
- git.kernel.org/stable/c/0cb85377daaefb4ce5ce72975f2deb27ee0e0cad (opens in a new tab)
- git.kernel.org/stable/c/7a1c293e7aa17f1afaee0684e0e931fe23a5a6b1 (opens in a new tab)
- git.kernel.org/stable/c/b02948a23455f8190a53887b2d2c13ae1d360cea (opens in a new tab)
- git.kernel.org/stable/c/e1ca4e3a380ef3e8f46ce006f1146392e3f32c98 (opens in a new tab)
- git.kernel.org/stable/c/1f7745fb3580152ca902ef181b605f33cabfb1d0 (opens in a new tab)
- git.kernel.org/stable/c/88c673a0bd233df44ca0020da82f4fd3876de27a (opens in a new tab)
- git.kernel.org/stable/c/c68e0068a236f9a7dfc19720bdf11e5d80a85089 (opens in a new tab)
- git.kernel.org/stable/c/9d9c5c218ea356a1d88765214ad2919605280ab1 (opens in a new tab)