NVD / CVE Program· CNA Linux

CVE-2026-31703: writeback: Fix use after free in inode_switch_wbs_work_fn()

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: 0.11% (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 028103656b84273c73e9e271cf95c9f3421f4b8a, 156cc63691c1f20905510b1007896e090355e6c2, 19ec404b079be057b387643ba0c69bbcc5867c35.

Low priority for now. Upgrade to Linux Linux 028103656b84273c73e9e271cf95c9f3421f4b8a, 156cc63691c1f20905510b1007896e090355e6c2, 19ec404b079be057b387643ba0c69bbcc5867c35 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: Fix use after free in inode_switch_wbs_work_fn() inode_switch_wbs_work_fn() has a loop like: wb_get(new_wb); while (1) { list = llist_del_all(&new_wb->switch_wbs_ctxs); /* Nothing to do? */ if (!list) break; ... process the items ... } Now adding of items to the list looks like: wb_queue_isw() if (llist_add(&isw->list, &wb->switch_wbs_ctxs)) queue_work(isw_wq, &wb->switch_work); Because inode_switch_wbs_work_fn() loops when processing isw items, it can happen that wb->switch_work is pending while wb->switch_wbs_ctxs is empty. This is a problem because in that case wb can get freed (no isw items -> no wb reference) while the work is still pending causing use-after-free issues. We cannot just fix this by cancelling work when freeing wb because that could still trigger problematic 0 -> 1 transitions on wb refcount due to wb_get() in inode_switch_wbs_work_fn(). It could be all handled with more careful code but that seems unnecessarily complex so let's avoid that until it is proven that the looping actually brings practical benefit. Just remove the loop from inode_switch_wbs_work_fn() instead. That way when wb_queue_isw() queues work, we are guaranteed we have added the first item to wb->switch_wbs_ctxs and nobody is going to remove it (and drop the wb reference it holds) until the queued work runs.

HighCVSS 7.8 · v3.1—No exploit Fix available

Memory safety

openSUSE-SU-2026:10793-1

Published: May 1, 2026
Updated: Aug 20, 2026
EPSS: 0.1% · 1th percentile
CWE: CWE-416

Report tools

JSON

Action score

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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No public exploit code on record
A fix has been released

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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.

Vendor	Product	CPE
linux	linux kernel	cpe:2.3:o:linux:linux_kernel

Affected versions

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

linux linux kernel6.18 and later · before 6.18.25
linux linux kernel6.19 and later · before 7.0.2
linux linux kernel7.1

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
- 6.18affected
- d072b38a64ddbc2d58c2e525a24af24ecbfebcb7 and later · before 382cf81cae89e58d22b4bdc38891cd4d0b9ba921affected · git
- ac7b2c21f2269d815ad0cdf0f8258d55185b805c and later · before 19ec404b079be057b387643ba0c69bbcc5867c35affected · git
- fabfc1fcddc5d8185722d4fde5f0968c4760b71e and later · before 156cc63691c1f20905510b1007896e090355e6c2affected · git
- e1b849cfa6b61f1c866a908c9e8dd9b5aaab820b and later · before 028103656b84273c73e9e271cf95c9f3421f4b8aaffected · git
- e1b849cfa6b61f1c866a908c9e8dd9b5aaab820b and later · before 9223e5f30403a9b506d6d0bff4f2e29a2d7d46afaffected · git
- e1b849cfa6b61f1c866a908c9e8dd9b5aaab820b and later · before 6689f01d6740cf358932b3e97ee968c6099800d9affected · git
- before 6.18not affected · semver
- 6.18.25 and later · up to and including 6.18.*not affected · semver
- 7.0.2 and later · up to and including 7.0.*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:14	linux	before 7.0.3-1	7.0.3-1
openSUSE:Tumbleweed	kernel-source	before 7.0.7-1.1	7.0.7-1.1

Same product

linux: all records

Other highest-scoring records for the same primary product.

CVE-2026-31431crypto: algif_aead - Revert to operating out-of-placeKEV
90Now
CVE-2022-0847A flaw was found in the way the "flags" member of the new pipe buffer structure was lacking proper initialization in copy_page_to_iter_pipe KEV
89Now
CVE-2021-22555Heap Out-Of-Bounds Write in Netfilter IP6T_SO_SET_REPLACEKEV
85Now

Published before and after this one in the same product

← EarlierCVE-2026-31695May 1, 2026 · wifi: virt_wifi: remove SET_NETDEV_DEV to avoid use-after-free
31Monitor
← EarlierCVE-2026-31702May 1, 2026 · f2fs: fix use-after-free of sbi in f2fs_compress_write_end_io()
31Monitor
Later →CVE-2026-31710May 1, 2026 · smb: client: fix dir separator in SMB1 UNIX mounts
22Monitor

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	028103656b84273c73e9e271cf95c9f3421f4b8a	Vendor (CNA)
Linux Linux	156cc63691c1f20905510b1007896e090355e6c2	Vendor (CNA)
Linux Linux	19ec404b079be057b387643ba0c69bbcc5867c35	Vendor (CNA)
Linux Linux	382cf81cae89e58d22b4bdc38891cd4d0b9ba921	Vendor (CNA)
Linux Linux	6689f01d6740cf358932b3e97ee968c6099800d9	Vendor (CNA)
Linux Linux	9223e5f30403a9b506d6d0bff4f2e29a2d7d46af	Vendor (CNA)
debian:linux	7.0.3-1 · Debian:14	Package registry (OSV)
opensuse:kernel-source	7.0.7-1.1 · openSUSE:Tumbleweed	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.

No dated events beyond publication.

No history yet (it accumulates with the daily EPSS job).

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).

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)

CWE-416 · Use After Free

CVSS vector

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

nvd-secondary

Root cause

After a memory region is freed, another reference pointing to it is still used. By then, the same region may have been allocated for different data.

The bug in code

The whole CWE-416 class

A representative example of this vulnerability class. Not the vendor's source code; it shows the faulty pattern and its fix.

Vulnerable

1free(dev->buf);
2/* ... another thread is still running ... */
3process(dev->buf);

Fixed

1lock(&dev->lock);
2free(dev->buf);
3dev->buf = NULL;
4unlock(&dev->lock);

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

Fix✗ → ✓Sep 28, 2026, 10:09 PM UTC

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

References

git.kernel.org/stable/c/028103656b84273c73e9e271cf95c9f3421f4b8a

Show all references (8 more)

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

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