CVE-2026-98536: writeback: report a Tasks-RCU quiescent state per cgwb drain pass
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 260f586a80e7f624dd7f069898a75a904f34d373, 407a5d205179a4ab186571b0e16ec42725dc77bc, 42462b5bb0dec57db7f85d0f77655c737d45754d; 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 260f586a80e7f624dd7f069898a75a904f34d373, 407a5d205179a4ab186571b0e16ec42725dc77bc, 42462b5bb0dec57db7f85d0f77655c737d45754d; 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: report a Tasks-RCU quiescent state per cgwb drain pass cleanup_offline_cgwbs_workfn() drains a dying cgwb by calling cleanup_offline_cgwb() until it returns false, with a cond_resched() between passes. On a CONFIG_PREEMPTION kernel that cond_resched() does nothing: _cond_resched() is a plain "return 0", and under PREEMPT_DYNAMIC the full and lazy modes disable it. Since commit 7dadeaa6e851 ("sched: Further restrict the preemption modes") those are the only two models on the architectures with PREEMPT_LAZY support, arm64 and x86 among them, so the drain loop never reports a Tasks-RCU quiescent state. A worker draining a cgwb with millions of attached inodes runs for minutes. On a 6.18 arm64 host in lazy mode the cgwb worker drained one dying cgroup's writeback domain for over 11 minutes. A BPF program unlink (bpf_trampoline_unlink_prog -> bpf_trampoline_update -> unregister_ftrace_direct -> ftrace_shutdown -> synchronize_rcu_tasks()) waited on that grace period while holding the trampoline mutex, 42 tasks queued behind it in D state, and the hung task detector fired at 614 s and panicked the host. Any BPF or ftrace detach during a long drain inherits the drain's length. Fix this by calling cond_resched_tasks_rcu_qs() so we do not stall out anybody who calls sycnrhonize_rcu_tasks(). We put this in a do { } while loop because if we have many small cgroups cleanup_offline_cgwb() will return false and we will never call cond_resched_tasks_rcu_qs(), creating the same problem.
- Published
- Oct 18, 2026
- Updated
- Oct 19, 2026
- EPSS
- 0.2% · 11th percentile
- CWE
- —
Report tools
Action score
0
Monitor
Low priority for now.
- CVSS
- 0 / 40 · —
- CISA KEV
- 0 / 30 · Not listed
- EPSS
- 0 / 30 · 0.2%
Get told when this record changes
- Not in KEV: no record of exploitation in the wild
- No public exploit code on record
- A fix has been released
If any of these changes, we'll tell you in the daily email digest.
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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.
We use this product, ask for helpAffected 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 863049b4018237d1590cd13b16e9fe9c0faad2c6affected · git
- c22d70a162d3cc177282c4487be4d54876ca55c8 and later · before 42462b5bb0dec57db7f85d0f77655c737d45754daffected · git
- c22d70a162d3cc177282c4487be4d54876ca55c8 and later · before ebf1555ad2821be06f87a88ffd9a2cab8d2200e1affected · git
- c22d70a162d3cc177282c4487be4d54876ca55c8 and later · before 4eb889649eaf65f4a5727b04ba1c017b7d05bb16affected · git
- c22d70a162d3cc177282c4487be4d54876ca55c8 and later · before fd3bf32279df98751364b3609eb100a3e42f253baffected · git
- c22d70a162d3cc177282c4487be4d54876ca55c8 and later · before 260f586a80e7f624dd7f069898a75a904f34d373affected · git
- c22d70a162d3cc177282c4487be4d54876ca55c8 and later · before 407a5d205179a4ab186571b0e16ec42725dc77bcaffected · git
- before 5.14not affected · semver
- 5.15.222 and later · up to and including 5.15.*not affected · semver
Package-level exposure
OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.
| Ecosystem | Package | Affected range | Fix |
|---|---|---|---|
| Debian:12 | linux | before 6.1.190-1 | 6.1.190-1 |
| Debian:12 | linux-6.12 | before 6.12.113-1~deb12u1 | 6.12.113-1~deb12u1 |
| Debian:13 | linux | before 6.12.113-1 | 6.12.113-1 |
| Debian:14 | linux | before 7.2.9-1 | 7.2.9-1 |
Same product
linux: all recordsOther highest-scoring records for the same primary product.
- CVE-2026-74705udp: fix potential use-after-free in tunnel segmentation40Plan
- CVE-2026-74612veth: fix skb length accounting after XDP frag adjustment40Plan
- CVE-2026-74475vxlan: use neigh_ha_snapshot() in route_shortcircuit()40Plan
Published before and after this one in the same product
- ← EarlierCVE-2026-98534Oct 18, 2026 · ipe: fix use-after-free when auditing a newly loaded policy0Monitor
- ← EarlierCVE-2026-98535Oct 18, 2026 · fsl/fman: Fix clk reference leak in read_dts_node()0Monitor
- Later →CVE-2026-98537Oct 18, 2026 · workqueue: Fix NULL current_pwq deref in flush dependency check0Monitor
Remediation
Which version to upgrade to
Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.
| Product / package | Fixed version | Source |
|---|---|---|
| Linux Linux | 260f586a80e7f624dd7f069898a75a904f34d373 | Vendor (CNA) |
| Linux Linux | 407a5d205179a4ab186571b0e16ec42725dc77bc | Vendor (CNA) |
| Linux Linux | 42462b5bb0dec57db7f85d0f77655c737d45754d | Vendor (CNA) |
| Linux Linux | 4eb889649eaf65f4a5727b04ba1c017b7d05bb16 | Vendor (CNA) |
| Linux Linux | 863049b4018237d1590cd13b16e9fe9c0faad2c6 | Vendor (CNA) |
| Linux Linux | ebf1555ad2821be06f87a88ffd9a2cab8d2200e1 | Vendor (CNA) |
| Linux Linux | fd3bf32279df98751364b3609eb100a3e42f253b | Vendor (CNA) |
| azl3 kernel 6.6.157.1-1 on Azure Linux 3.0 | 6.6.159.1-1 · Release Notes | Microsoft (MSRC) |
| debian:linux | 6.1.190-1 · Debian:12 | Package registry (OSV) |
| debian:linux-6.12 | 6.12.113-1~deb12u1 · Debian:12 | Package 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.
- Published
- Fix recordedsame day
- TodayNov 5, 2026+18 d
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 researchersFinders, 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.
- TR-26-1351 · Oct 19, 2026(Linux Kernel Güvenlik Bildirimi)
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
- Exploit maturity— → none
- Fix✗ → ✓
For records you follow, these changes also arrive as notifications. →
References
Show all references (6 more)Show less
- git.kernel.org/stable/c/407a5d205179a4ab186571b0e16ec42725dc77bc
- git.kernel.org/stable/c/42462b5bb0dec57db7f85d0f77655c737d45754d
- git.kernel.org/stable/c/4eb889649eaf65f4a5727b04ba1c017b7d05bb16
- git.kernel.org/stable/c/863049b4018237d1590cd13b16e9fe9c0faad2c6
- git.kernel.org/stable/c/ebf1555ad2821be06f87a88ffd9a2cab8d2200e1
- git.kernel.org/stable/c/fd3bf32279df98751364b3609eb100a3e42f253b
Vendor advisories and official records. Exploit/PoC links are deliberately left out.