VulnerabilityPublished 23 Oct 2026

CVE-2026-98983: Linux kernel · unshare: don't drop active namespace references that were never taken

Affects Linux kernelSource CVE Database V5

Not known to be exploited · fixed in 56fe03a0c05dba4c5f6a23c391f96de1614a098c : update Linux kernel when convenient.

Data as of 26 Oct 2026, 17:30 UTC

Severity

Medium

Rated Medium by Threat Radar's AI analysis · CVSS not yet scored by NVD

EPSS: 0.1% chance of exploitation in 30 days – higher than 5% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 56fe03a0c05dba4c5f6a23c391f96de1614a098c, 7.1, 6.19 +5

Exploitation evidence

Disclosed: evidence found.
CVE published 23 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.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Upgrade to a fixed release listed under Affected software.

Affected software

Product	Affected	Fixed in
LinuxLinux	Affected >=5.15.209 <5.16 >=6.1.175 <6.2 >=6.6.141 <6.7 >=6.12.91 <6.13 >=6.18.33 <6.19 >=7.0.10 <7.1	Fixed in 56fe03a0c05dba4c5f6a23c391f96de1614a098c 7.1 6.19 6.13 6.7 6.2 5.16 0b6f31a3c0b16066f812e94b52a704174a6f23cd
LinuxLinux	Affected =7.1	Fixed in–

AI-suggested

This vulnerability has been fixed in Linux kernel versions 5.16, 6.2, 6.7, 6.13, 6.19, and 7.1 and later. Users and administrators should upgrade to these fixed versions or later to remediate the issue. No additional mitigation actions are indicated.

Description

A vulnerability in the Linux kernel's unshare system call could cause active namespace references to be dropped incorrectly when set_cred_ucounts() fails during unshare. This leads to namespace reference counts going negative and the caller losing references to namespaces it continues to use, causing those namespaces to no longer appear in namespace listings. The issue affects multiple Linux kernel versions and has been fixed in later releases.

Impact

The vulnerability causes namespace reference counts to become inconsistent, leading to namespaces that the caller still uses being dropped from namespace listings. This could potentially disrupt namespace management and visibility for affected processes. There is no indication of direct exploitation or privilege escalation from the provided data.

Summary

The Linux kernel vulnerability CVE-2026-98983 involves improper handling of active namespace references in the unshare system call. Specifically, ksys_unshare() calls put_nsproxy() on an nsproxy that was never installed when set_cred_ucounts() fails, causing the reference counts of new namespaces to decrement below zero. This results in the caller losing references to namespaces it still uses, making those namespaces disappear from listns() output. The flaw occurs only when set_cred_ucounts() fails, which happens if alloc_ucounts() cannot allocate and the real UID differs from the effective UID. The issue has been addressed by separating the handling of nsproxy freeing for prepared but not installed nsproxies and applying this fix to unshare as well.

References

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 26 Oct 2026, 09:54 UTC

Technical details

References

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