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CVE.org (no NVD analysis yet)· CNA Linux

CVE-2026-99180: unicode: free the map after a grace period

Noroxi assessment

Priority: Monitor (action score 31/100)

  • The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
  • Probability of exploitation in the next 30 days: 0.13% (FIRST EPSS).
  • 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.
  • Fixed version: Linux Linux 092e14e1479a39157ca01668d43e4649793f39ed, 2b54d3c971a1e5df3c9b0bcc10311ae6c29e79d8, 5d7687b0b71601cc32f1bfd62f56cf5eea3e5a07; azl3 kernel 6.6.157.1-1 on Azure Linux 3.0 Release Notes; azl3 kernel 6.6.159.1-1 on Azure Linux 3.0 Release Notes.
  • Mentioned 1 time in Turkish national cyber security advisories (siberguvenlik.gov.tr).

Low priority for now. Upgrade to Linux Linux 092e14e1479a39157ca01668d43e4649793f39ed, 2b54d3c971a1e5df3c9b0bcc10311ae6c29e79d8, 5d7687b0b71601cc32f1bfd62f56cf5eea3e5a07; azl3 kernel 6.6.157.1-1 on Azure Linux 3.0 Release Notes; azl3 kernel 6.6.159.1-1 on Azure Linux 3.0 Release Notes or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

In the Linux kernel, the following vulnerability has been resolved: unicode: free the map after a grace period generic_ci_d_hash() and generic_ci_d_compare() read sb->s_encoding and dereference the unicode map while a pathwalk in rcu mode holds nothing but rcu_read_lock(). The filesystems that use them, ext4, f2fs and tmpfs, drop the map with utf8_unload() from ->put_super(), which runs when the last reference to the mount goes away. A lookup that is still inside such a filesystem at that point reads a freed map. With a pathwalk held up in utf8_casefold_hash() while the last reference to a casefolded tmpfs goes away: BUG: KASAN: slab-use-after-free in utf8nlookup+0x74c/0x950 Read of size 8 at addr ff110001030fe658 by task walker/98 Call Trace: <TASK> utf8nlookup+0x74c/0x950 utf8byte+0x160/0x1560 utf8_casefold_hash+0x167/0x230 generic_ci_d_hash+0xdd/0x1c0 link_path_walk+0x11ad/0x1d30 path_lookupat+0x63/0xb00 filename_lookup+0x1f1/0x5b0 vfs_statx+0xd7/0x3b0 [...] Allocated by task 94: __kmalloc_cache_noprof+0x249/0x560 utf8_load+0x4e/0x570 shmem_parse_opt_casefold.isra.0+0x92/0x270 [...] Freed by task 97: kfree+0x1db/0x5b0 shmem_put_super+0x72/0x170 generic_shutdown_super+0x14c/0x530 kill_anon_super+0x3a/0x60 deactivate_locked_super+0x9c/0xf0 cleanup_mnt+0x9f/0x130 So far that has been hard to hit. umount(2) waits for a grace period in namespace_unlock() before it drops the mount, so only a mount whose last reference goes away elsewhere, like the close of a file or a chdir out of a lazily unmounted directory, can race a walker. So it is reachable. Delay the free until a grace period has passed. The map and the data table it holds a reference to then outlive any pathwalk that found the superblock before the mount went away. The reference on the data table module is dropped from the rcu callback as well. utf8-core is built in whenever CONFIG_UNICODE is set, so there is no module exit that would have to wait for the callbacks. Overlayfs points the s_encoding of an overlay at the map of its first layer without taking a reference of its own. That stays correct. The layer is held by the overlay, so its map is dropped only after the overlay is gone.

HighCVSS 7.8 · v3.1—No exploit Fix available
Published
Oct 28, 2026
Updated
Oct 31, 2026
EPSS
0.1% · 2th percentile
CWE
—

Report tools

JSON

Action score

31

Monitor

Low priority for now.

CVSS
31 / 40 · 7.8 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.1%

CNA vs NVD score

NVD
—
CNA · Linux
7.8
NVD has not scored this yet; the score shown is the CNA’s.

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

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  • Not in KEV: no record of exploitation in the wild
  • No public exploit code on record
  • A fix has been released

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  • when exploit code appears or is weaponized
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  • when EPSS rises 20 points in a week

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

—

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

    • 5.2affected
    • b886ee3e778ec2ad43e276fd378ab492cf6819b7 and later · before 092e14e1479a39157ca01668d43e4649793f39edaffected · git
    • b886ee3e778ec2ad43e276fd378ab492cf6819b7 and later · before 6472455f2b015cad43adb790cb63fe1d3cff2f57affected · git
    • b886ee3e778ec2ad43e276fd378ab492cf6819b7 and later · before f96c2731a105d6663c606388f5dc21781e00ade5affected · git
    • b886ee3e778ec2ad43e276fd378ab492cf6819b7 and later · before 5d7687b0b71601cc32f1bfd62f56cf5eea3e5a07affected · git
    • b886ee3e778ec2ad43e276fd378ab492cf6819b7 and later · before 69a0d6b31d05e856c7335509222f25321e3c69caaffected · git
    • b886ee3e778ec2ad43e276fd378ab492cf6819b7 and later · before 2b54d3c971a1e5df3c9b0bcc10311ae6c29e79d8affected · git
    • b886ee3e778ec2ad43e276fd378ab492cf6819b7 and later · before 6560c3d9a6925e3747d9ad8463e16010c31ba715affected · git
    • b886ee3e778ec2ad43e276fd378ab492cf6819b7 and later · before a96c5299bd7305eb984377681eb3222a57376405affected · git
    • before 5.2not affected · semver

Package-level exposure

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

EcosystemPackageAffected rangeFix
Debian:12linuxfrom 0—
Debian:13linuxbefore 6.12.115-26.12.115-2

Same product

linux: all records

Other highest-scoring records for the same primary product.

  • CVE-2026-74705udp: fix potential use-after-free in tunnel segmentation
    40Plan
  • CVE-2026-74612veth: fix skb length accounting after XDP frag adjustment
    40Plan
  • CVE-2026-74475vxlan: use neigh_ha_snapshot() in route_shortcircuit()
    40Plan

Published before and after this one in the same product

  • ← EarlierCVE-2026-99178Oct 28, 2026 · x86/kvm: Don't consume async #PF flags on a kernel #PF in NMI context
    0Monitor
  • ← EarlierCVE-2026-99179Oct 28, 2026 · watch_queue: Fix note pool publication race in watch_queue_set_size()
    0Monitor
  • Later →CVE-2026-99181Oct 28, 2026 · autofs: ignore notification errors from a replaced pipe
    0Monitor

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 Linux092e14e1479a39157ca01668d43e4649793f39edVendor (CNA)
Linux Linux2b54d3c971a1e5df3c9b0bcc10311ae6c29e79d8Vendor (CNA)
Linux Linux5d7687b0b71601cc32f1bfd62f56cf5eea3e5a07Vendor (CNA)
Linux Linux6472455f2b015cad43adb790cb63fe1d3cff2f57Vendor (CNA)
Linux Linux6560c3d9a6925e3747d9ad8463e16010c31ba715Vendor (CNA)
Linux Linux69a0d6b31d05e856c7335509222f25321e3c69caVendor (CNA)
Linux Linuxa96c5299bd7305eb984377681eb3222a57376405Vendor (CNA)
Linux Linuxf96c2731a105d6663c606388f5dc21781e00ade5Vendor (CNA)
azl3 kernel 6.6.157.1-1 on Azure Linux 3.0Release NotesMicrosoft (MSRC)
azl3 kernel 6.6.159.1-1 on Azure Linux 3.0Release NotesMicrosoft (MSRC)
debian:linux6.12.115-2 · Debian:13Package 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.

  1. Published
  2. Fix recordedsame day
  3. TodayNov 6, 2026+9 d
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.

No nightly-computed relations.

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).

National notice (Türkiye Cybersecurity Directorate / USOM)

Official security notices citing this record; remediation advice is on the agency's page.

All national notices →

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

Weakness class (CWE)

—

CVSS vector

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

nvd-secondary

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. CVSS— → 7.8
  2. Severity— → high
  3. Exploit maturity— → none
  4. Fix✗ → ✓

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

References

Show all references (7 more)

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

All records