Vulnerability in Linux kernel (CVE-2026-90139)
Summary
Vulnerability in Linux kernel (CVE-2026-90139). Risk of unauthorized operations or information disclosure.
Original description
The description as published by the source.
In the Linux kernel, the following vulnerability has been resolved:
fuse: check for NULL root inode in fuse_fill_super_submount
fuse_iget() can return NULL when its inode allocation fails, but
fuse_fill_super_submount() passed the result straight to get_fuse_inode()
and decremented fi->nlookup without checking it:
root = fuse_iget(sb, parent_fi->nodeid, ...);
fi = get_fuse_inode(root);
fi->nlookup--;
Inside fuse_iget() the inode allocation can fail and return NULL. The
submount root takes the iget5_locked() path, whose alloc_inode() can fail
under memory pressure (the auto-submount branch can fail the same way in
new_inode() or fuse_alloc_submount_lookup()):
inode = iget5_locked(sb, nodeid, fuse_inode_eq, fuse_inode_set,
&nodeid);
if (!inode)
return NULL;
A NULL root makes get_fuse_inode() a container_of() on NULL and the
nlookup decrement a write to a bogus address, oopsing the mount. With
CONFIG_KASAN the following null pointer dereference is reported when the
root inode allocation of an auto-submount fails (e.g. under memory
pressure):
==================================================================
BUG: KASAN: null-ptr-deref in fuse_get_tree_submount+0x656/0x8b0
Read of size 8 at addr 00000000000002b0 by task ls/942
CPU: 0 PID: 942 Comm: ls Tainted: G W 6.6 #15
Call Trace:
fuse_get_tree_submount+0x656/0x8b0
vfs_get_tree+0x48/0x140
fc_mount+0x13/0x50
fuse_dentry_automount+…
Source: NIST National Vulnerability Database NVD GitHub Advisory
Auto-generated summary
Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.
A vulnerability tracked as CVE-2026-90139 has been found in Linux kernel.
Risk of unauthorized operations or information disclosure.
What to do: apply the vendor's official patched release.
If unsure, ask your IT team or search "Linux kernel CVE-2026-90139" on the vendor's site.
CVE-2026-90139 (Linux kernel)
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.
A vulnerability (unclassified) exists in Linux kernel.
Check the vendor advisory for the affected versions of Linux kernel.
Severity: ?. Risk of unauthorized operations or information disclosure.
Update to the patched release per vendor advisory.
Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.
Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Audit SBOM/dependencies to find affected services.
Response actions
Concrete steps and command examples for SOC/SRE teams to execute in order
-
1Identify exposure identify
Audit SBOM/dependencies for affected components.資産台帳・SBOM・依存マニフェストで Linux kernel を使っているサービスとバージョンを洗い出す。
-
2Post-deployment verification verify
Confirm patched version is live in productionパッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。
Fix status by distribution
Fixed packages published by each distribution for this CVE
- Ubuntu UBUNTU-CVE-2026-90139 linux-hwe-edge
References
- web git.kernel.org
- web git.kernel.org
- web git.kernel.org
- web git.kernel.org
- web git.kernel.org
- web nvd.nist.gov
- web github.com