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CVE-2026-43472· NVD / CVE Program· CNA Linux

unshare: fix unshare_fs() handling

In the Linux kernel, the following vulnerability has been resolved: unshare: fix unshare_fs() handling There's an unpleasant corner case in unshare(2), when we have a CLONE_NEWNS in flags and current->fs hadn't been shared at all; in that case copy_mnt_ns() gets passed current->fs instead of a private copy, which causes interesting warts in proof of correctness] > I guess if private means fs->users == 1, the condition could still be true. Unfortunately, it's worse than just a convoluted proof of correctness. Consider the case when we have CLONE_NEWCGROUP in addition to CLONE_NEWNS (and current->fs->users == 1). We pass current->fs to copy_mnt_ns(), all right. Suppose it succeeds and flips current->fs->{pwd,root} to corresponding locations in the new namespace. Now we proceed to copy_cgroup_ns(), which fails (e.g. with -ENOMEM). We call put_mnt_ns() on the namespace created by copy_mnt_ns(), it's destroyed and its mount tree is dissolved, but... current->fs->root and current->fs->pwd are both left pointing to now detached mounts. They are pinning those, so it's not a UAF, but it leaves the calling process with unshare(2) failing with -ENOMEM _and_ leaving it with pwd and root on detached isolated mounts. The last part is clearly a bug. There is other fun related to that mess (races with pivot_root(), including the one between pivot_root() and fork(), of all things), but this one is easy to isolate and fix - treat CLONE_NEWNS as "allocate a new fs_struct even if it hadn't been shared in the first place". Sure, we could go for something like "if both CLONE_NEWNS *and* one of the things that might end up failing after copy_mnt_ns() call in create_new_namespaces() are set, force allocation of new fs_struct", but let's keep it simple - the cost of copy_fs_struct() is trivial. Another benefit is that copy_mnt_ns() with CLONE_NEWNS *always* gets a freshly allocated fs_struct, yet to be attached to anything. That seriously simplifies the analysis... FWIW, that bug had been there since the introduction of unshare(2) ;-/

MediumCVSS 5.5 · v3.1—No exploit Fix available
Published
May 8, 2026
Updated
Jun 17, 2026
EPSS
0.2% · 5th percentile
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Report tools

JSON

Action score

22

Monitor

Low priority for now.

CVSS
22 / 40 · 5.5 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.2%

Noroxi analysis

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Affected systems

VendorProduct
linuxlinux kernel

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • linux linux kernel2.6.16.1 and later · before 5.10.253
  • linux linux kernel5.11 and later · before 5.15.203
  • linux linux kernel5.16 and later · before 6.1.167
  • linux linux kernel6.2 and later · before 6.6.130
  • linux linux kernel6.7 and later · before 6.12.78
  • linux linux kernel6.13 and later · before 6.18.19
  • linux linux kernel6.19 and later · before 6.19.9
  • linux linux kernel2.6.16
  • linux linux kernel7.0

Versions reported by the vendor

Affected version ranges reported by the assigning authority (Linux). Independent of NVD's CPE analysis and usually ahead of it.

  • Linux Linux

    • 2.6.16affected
    • 741a295130606143edbf9fc740f633dbc1e6225f and later · before 845bf3c6963a52096d0d3866e4a92db77a0c03d8affected · git
    • 741a295130606143edbf9fc740f633dbc1e6225f and later · before d3ffc8f13034af895531a02c30b1fe3a34b46432affected · git
    • 741a295130606143edbf9fc740f633dbc1e6225f and later · before d0d99f60538ddb4a62ccaac2168d8f448965f083affected · git
    • 741a295130606143edbf9fc740f633dbc1e6225f and later · before d7963d6997fea86a6def242ac36198b86655f912affected · git
    • 741a295130606143edbf9fc740f633dbc1e6225f and later · before aa9ebc084505fb26dd90f4d7a249045aad152043affected · git
    • 741a295130606143edbf9fc740f633dbc1e6225f and later · before af8f4be3b68ac8caa41c8e5ead0eeaf5e85e42d0affected · git
    • 741a295130606143edbf9fc740f633dbc1e6225f and later · before 42e21e74061b0ebbd859839f81acf10efad02a27affected · git
    • 741a295130606143edbf9fc740f633dbc1e6225f and later · before 6c4b2243cb6c0755159bd567130d5e12e7b10d9faffected · git
    • before 2.6.16not affected · semver

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
Debian:12linuxbefore 6.1.170-16.1.170-1
Debian:13linuxbefore 6.12.85-16.12.85-1
Debian:14linuxbefore 6.19.10-16.19.10-1

Same product

linux: all records

Other highest-scoring records for the same primary product.

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  • CVE-2016-5195Race condition in mm/gup.c in the Linux kernel 2.x through 4.x before 4.8.3 allows local users to gain privileges by leveraging incorrect haKEV
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Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
Linux Linux42e21e74061b0ebbd859839f81acf10efad02a27Vendor (CNA)
Linux Linux6c4b2243cb6c0755159bd567130d5e12e7b10d9fVendor (CNA)
Linux Linux845bf3c6963a52096d0d3866e4a92db77a0c03d8Vendor (CNA)
Linux Linuxaa9ebc084505fb26dd90f4d7a249045aad152043Vendor (CNA)
Linux Linuxaf8f4be3b68ac8caa41c8e5ead0eeaf5e85e42d0Vendor (CNA)
Linux Linuxd0d99f60538ddb4a62ccaac2168d8f448965f083Vendor (CNA)
Linux Linuxd3ffc8f13034af895531a02c30b1fe3a34b46432Vendor (CNA)
Linux Linuxd7963d6997fea86a6def242ac36198b86655f912Vendor (CNA)
debian:linux6.1.170-1 · Debian:12Package registry (OSV)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

EPSS, last 120 days

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

No commit or PR link among the references.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

  • CVE-2024-50302536 days apartHID: core: zero-initialize the report bufferKEV
    52Plan
  • CVE-2026-5298947 days apartnvmet-tcp: propagate nvmet_tcp_build_pdu_iovec() errors to its callers
    39Monitor
  • CVE-2026-5322548 days apartsctp: fix uninit-value in __sctp_rcv_asconf_lookup()
    36Monitor
  • CVE-2026-5317048 days apartaccel/ethosu: reject DMA commands with uninitialized length
    35Monitor
  • CVE-2026-431392 days apartxfrm6: fix uninitialized saddr in xfrm6_get_saddr()
    34Monitor
  • CVE-2026-432910 days apartnet: nfc: nci: Fix parameter validation for packet data
    33Monitor

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

Technical details

Attack conditions

  • Someone with local access to the system can trigger it.
  • A low-privileged account is enough.
  • No user action is required.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
none
Integrity
none
Availability
high · the service can be disrupted
Attack vector
Local
Attack complexity
Low
Privileges required
Low
User interaction
None
Scope
Unchanged
Confidentiality impact
None
Integrity impact
None
Availability impact
High

Weakness class (CWE)

CWE-908 · Use of Uninitialized Resource

CVSS vector

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

nvd-primary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

MITRE has no CAPEC/ATT&CK mapping for this CWE.

Change log

  1. Fix✗ → ✓

For records you follow, these changes also arrive as notifications. →

References

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records