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

CVE-2026-98538: writeback: bound cleanup_offline_cgwb() rescans by rotating scanned inodes

Noroxi assessment

Priority: Monitor (action score 0/100)

  • 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: 0.21% (FIRST EPSS).
  • Fixed version: Linux Linux 2d1da58c79b66646721a644c6eb4dd1f9c5c9327, 624dd0931162523d70f9db8c120b5ec6429a9b97, 9dac137bf77e0683778fb34c86e730c6129e8cb6; azl3 kernel 6.6.157.1-1 on Azure Linux 3.0 6.6.159.1-1.
  • Mentioned 1 time in Turkish national cyber security advisories (siberguvenlik.gov.tr).

Low priority for now. Upgrade to Linux Linux 2d1da58c79b66646721a644c6eb4dd1f9c5c9327, 624dd0931162523d70f9db8c120b5ec6429a9b97, 9dac137bf77e0683778fb34c86e730c6129e8cb6; azl3 kernel 6.6.157.1-1 on Azure Linux 3.0 6.6.159.1-1 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: writeback: bound cleanup_offline_cgwb() rescans by rotating scanned inodes cleanup_offline_cgwb() prepares at most WB_MAX_INODES_PER_ISW inodes per call and is called again until the dying wb is drained, but every call walks wb->b_attached and then wb->b_dirty_time from the same end. Inodes already prepared (they stay on the list with I_WB_SWITCH set until the switch worker runs) and inodes that cannot be switched (I_FREEING, I_WILL_FREE, !SB_ACTIVE, DAX, already on the target wb) stay where they are, so each pass rescans a growing run of them under wb->list_lock and a full drain is quadratic in the number of inodes on the list. With ~17M inodes attached to one dying cgwb we saw this end in soft lockups, with CPUs reported stuck for 21-48s. Walk both lists from the oldest end and move every scanned inode to the newest end, so the next pass starts where the previous one stopped and the drain becomes linear. b_attached is unordered, so nobody sees the reorder there. b_dirty_time is ordered by dirtied_when, but the oldest unscanned inode stays at the end move_expired_inodes() picks from, sync takes the whole list regardless of order, and prepared inodes leave the list as soon as the switch work runs and get a new dirtied_time_when on the new wb anyway, so the only inodes left out of order are the ones that can never switch (DAX), and only on the dying wb.

—No exploit Fix available
Published
Oct 18, 2026
Updated
Oct 19, 2026
EPSS
0.2% · 11th percentile
CWE
—

Report tools

JSON

Action score

0

Monitor

Low priority for now.

CVSS
0 / 40 · —
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.2%

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Noroxi analysis

What does it mean in your environment?

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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

    • 5.14affected
    • c22d70a162d3cc177282c4487be4d54876ca55c8 and later · before 2d1da58c79b66646721a644c6eb4dd1f9c5c9327affected · git
    • c22d70a162d3cc177282c4487be4d54876ca55c8 and later · before c96b4d1628868e1195da1a896f79e06f350a3187affected · git
    • c22d70a162d3cc177282c4487be4d54876ca55c8 and later · before 624dd0931162523d70f9db8c120b5ec6429a9b97affected · git
    • c22d70a162d3cc177282c4487be4d54876ca55c8 and later · before dd4b92067238771b604b59fdda8efed6d70ee823affected · git
    • c22d70a162d3cc177282c4487be4d54876ca55c8 and later · before 9dac137bf77e0683778fb34c86e730c6129e8cb6affected · git
    • c22d70a162d3cc177282c4487be4d54876ca55c8 and later · before f6988c90671e83db79df1b7b9d6fdb0e5947fd84affected · git
    • before 5.14not affected · semver
    • 6.1.189 and later · up to and including 6.1.*not affected · semver
    • 6.6.158 and later · up to and including 6.6.*not affected · semver

Package-level exposure

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

EcosystemPackageAffected rangeFix
Debian:12linuxbefore 6.1.190-16.1.190-1
Debian:12linux-6.12before 6.12.113-1~deb12u16.12.113-1~deb12u1
Debian:13linuxbefore 6.12.113-16.12.113-1
Debian:14linuxbefore 7.2.9-17.2.9-1

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-2026-98536Oct 18, 2026 · writeback: report a Tasks-RCU quiescent state per cgwb drain pass
    0Monitor
  • ← EarlierCVE-2026-98537Oct 18, 2026 · workqueue: Fix NULL current_pwq deref in flush dependency check
    0Monitor
  • Later →CVE-2026-98539Oct 18, 2026 · fs/ntfs3: use d_instantiate_new() in ntfs_create_inode() and murder syzbot's "WARNING in do_new_mount" saga
    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 Linux2d1da58c79b66646721a644c6eb4dd1f9c5c9327Vendor (CNA)
Linux Linux624dd0931162523d70f9db8c120b5ec6429a9b97Vendor (CNA)
Linux Linux9dac137bf77e0683778fb34c86e730c6129e8cb6Vendor (CNA)
Linux Linuxc96b4d1628868e1195da1a896f79e06f350a3187Vendor (CNA)
Linux Linuxdd4b92067238771b604b59fdda8efed6d70ee823Vendor (CNA)
Linux Linuxf6988c90671e83db79df1b7b9d6fdb0e5947fd84Vendor (CNA)
azl3 kernel 6.6.157.1-1 on Azure Linux 3.06.6.159.1-1 · Release NotesMicrosoft (MSRC)
debian:linux6.1.190-1 · Debian:12Package registry (OSV)
debian:linux-6.126.12.113-1~deb12u1 · 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.

  1. Published
  2. Fix recordedsame day
  3. TodayNov 2, 2026+14 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

No CVSS vector for this record, so attack conditions can't be derived.

Weakness class (CWE)

—

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. Exploit maturity— → none
  2. Fix✗ → ✓

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

References

Show all references (5 more)

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

All records