Medium Memory corruption

CVE-2026-46086 — net: bridge: use a stable FDB dst snapshot in RCU readers

In the Linux kernel, the following vulnerability has been resolved: net: bridge: use a stable FDB dst snapshot in RCU readers Local FDB entries can be rewritten in place by `fdb_delete_local()`, which updates `f->dst` to another port or to `NULL` while keeping the entry alive. Several bridge RCU readers inspect `f->dst`, including `br_fdb_fillbuf()` through the `brforward_read()` sysfs path. These readers currently load `f->dst` multiple times and can therefore observe inconsistent values across the check and later dereference. In `br_fdb_fillbuf()`, this means a concurrent local-FDB update can change `f->dst` after the NULL check and before the `port_no` dereference, leading to a NULL-ptr-deref. Fix this by taking a single `READ_ONCE()` snapshot of `f->dst` in each affected RCU reader and using that snapshot for the rest of the access sequence. Also publish the in-place `f->dst` updates in `fdb_delete_local()` with `WRITE_ONCE()` so the readers and writer use matching access patterns.

Published May 27, 2026 · Updated Oct 14, 2026 · Sources: NIST National Vulnerability Database, CVE Program (cve.org) e CISA ADP, GitHub Security Advisories · CNA: Linux

Low

Who exploits it and how urgent it is

A 0–100 score combining confirmed exploitation, ransomware and APT use, public exploits, EPSS and severity.

No exploitation signal in the sources consulted so far.

How the score was calculated

EPSS 0.1% (30-day exploitation probability)+0
Technical severity (medium)+3

The score orders the patch queue; it does not replace your asset context (internet exposure, criticality, compensating controls).

Triage

Is it exploited, how likely is exploitation, what does it touch, and how severe do the sources call it.

Exploitation

Not confirmed

Not in CISA KEV — an absence of record, not proof it is unexploited.

EPSS FIRST

0.13%

ahead of 2% of scored CVEs · Oct 14, 2026

Affects

Linux

Linux and 1 more

CVSS base

5.5

Medium · 2 source(s)

Remediation

Fixes and mitigations documented by the sources — linked to the original advisory.

Documented patch — git.kernel.org (NIST National Vulnerability Database)
Documented patch — git.kernel.org (NIST National Vulnerability Database)
Documented patch — git.kernel.org (NIST National Vulnerability Database)
Documented patch — git.kernel.org (NIST National Vulnerability Database)
Documented patch — git.kernel.org (NIST National Vulnerability Database)
Documented patch — git.kernel.org (NIST National Vulnerability Database)
Documented patch — git.kernel.org (NIST National Vulnerability Database)
Documented patch — git.kernel.org (NIST National Vulnerability Database)

First 24 hours

Ordered from the record’s own fields — exposure first, because you cannot patch what you have not found. A rule-generated starting point.

Identify exposed assets running the affected vendor/product/version combinations (Linux Linux, Linux Linux Kernel).
Apply the fixed version or the patch documented under Remediation.
Search available logs for exploit probes matching the vulnerability class (memory corruption), errors and authentication anomalies.

Affected scope

Vendor, product and versions as the sources word them.

Vendor	Product	Versions	Status	Source
Linux	Linux	version 3.14≥ 960b589f86c74ce582922fcb996103271081f4de and < df4601653201de21b487c3e7fffd464790cab808≥ 960b589f86c74ce582922fcb996103271081f4de and < 9a2d9d4e657b23dc21f24cf139e3aeff0b61341f≥ 960b589f86c74ce582922fcb996103271081f4de and < 5424e678f9b304e148cf5dcc047cffc7a56a3bb5≥ 960b589f86c74ce582922fcb996103271081f4de and < 81af4137a30c4c2dc694dea8cacb180bd66000ef≥ 960b589f86c74ce582922fcb996103271081f4de and < 0b9e4bbfb7c949151e3acd44ed4aa33614d2e110≥ 960b589f86c74ce582922fcb996103271081f4de and < 1406c4e0ed1eaf8a29801ab1163d00fb7ee4359a≥ 960b589f86c74ce582922fcb996103271081f4de and < a6ae4511c07b91f597e461406c6330f0d4ff810e and 1 more ≥ 960b589f86c74ce582922fcb996103271081f4de and < c502fa9f094cb03d1d1685c71e2105ab359bc2b8	Vulnerable	CVE Program (cve.org) e CISA ADP
Linux	Linux Kernel	version 3.14-rc6version 3.14-rc8version 3.14-rc7≥ 3.14.1 and < 5.10.259version 3.14-rc5version 3.14-rc4version 3.14-rc3version 3.14 and 6 more ≥ 6.19 and < 7.0.4≥ 6.13 and < 6.18.27≥ 6.7 and < 6.12.86≥ 6.2 and < 6.6.140≥ 5.16 and < 6.1.176≥ 5.11 and < 5.15.210	Vulnerable	NIST National Vulnerability Database

Attack characteristics

The CVSS vector, decoded. It describes the attack, not your exposure to it.

Attack vector

Local

Attack complexity

Low

Privileges required

Low

User interaction

None

Scope

Unchanged

Confidentiality

None

Integrity

None

Availability

High

Every base score collected

Sources score independently and may disagree; each row says who scored it and under which version.

Score	Version	Severity	Expl.	Impact	Scored by
5.5	CVSS 3.1	Medium	1.8	3.6	nvd@nist.gov via NIST National Vulnerability Database
5.5	CVSS 3.1	Medium	—	—	GitHub, Inc. via GitHub Security Advisories

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H (score shown at the top: nvd@nist.gov)

Weakness MITRE

Weakness class according to MITRE’s CWE catalog.

CWE-476 · NULL Pointer Dereference

Other CVEs with this weakness →

EPSS over time FIRST

Oct 13, 2026 → Oct 14, 2026 · 2 reading(s) · max 0.17%

Detection

Read off the CVSS vector and the weakness class. Starting points, not tested rules.

Local/physical vector: focus on endpoint telemetry (EDR) from affected hosts.
Correlate service crashes/restarts with inbound traffic; repeated crashes may indicate attempts.

endpoint telemetry (EDR)crash dumps

Timeline

What happened to this CVE, newest first.

2026
Affected products added · linux/linux
Oct 13, 2026 · CVE Program (cve.org) e CISA ADP
Record published
Oct 13, 2026
Fix documented
Oct 13, 2026 · NIST National Vulnerability Database
CVSS changed · 5.5
Oct 13, 2026 · NIST National Vulnerability Database
Source status changed · → Undergoing Analysis
Oct 13, 2026 · NIST National Vulnerability Database
Record created in this database
Oct 13, 2026 · NIST National Vulnerability Database
CVE published
May 27, 2026 · Linux

Source activity

Repeated readings are counted rather than listed.

2× References added · Oct 14, 2026 – Oct 14, 2026
1× Official description updated · Oct 13, 2026 – Oct 13, 2026

References

13 on the record

git.kernel.org/stable/c/81af4137a30c4c2dc694dea8cacb180bd66000ef
Patch, NIST National Vulnerability Database
git.kernel.org/stable/c/5424e678f9b304e148cf5dcc047cffc7a56a3bb5
Patch, NIST National Vulnerability Database
git.kernel.org/stable/c/a6ae4511c07b91f597e461406c6330f0d4ff810e
Patch, NIST National Vulnerability Database
git.kernel.org/stable/c/1406c4e0ed1eaf8a29801ab1163d00fb7ee4359a
Patch, NIST National Vulnerability Database
git.kernel.org/stable/c/0b9e4bbfb7c949151e3acd44ed4aa33614d2e110
Patch, NIST National Vulnerability Database
git.kernel.org/stable/c/c502fa9f094cb03d1d1685c71e2105ab359bc2b8
Patch, NIST National Vulnerability Database
git.kernel.org/stable/c/9a2d9d4e657b23dc21f24cf139e3aeff0b61341f
Patch, NIST National Vulnerability Database
git.kernel.org/stable/c/df4601653201de21b487c3e7fffd464790cab808
Patch, NIST National Vulnerability Database
nvd.nist.gov/vuln/detail/CVE-2026-46086
GitHub Security Advisories
cert-portal.siemens.com/productcert/html/ssa-457936.html
NIST National Vulnerability Database
cert-portal.siemens.com/productcert/html/ssa-019113.html
NIST National Vulnerability Database
cert-portal.siemens.com/productcert/html/ssa-784472.html
NIST National Vulnerability Database
github.com/advisories/GHSA-qcf5-mj4w-x99v
GitHub Security Advisories

Elsewhere on this site

Linux
every CVE for this vendor

Memory corruption
same class

CWE-476
other pages naming this weakness

Related CVEs (same products)

Critical CVE-2026-99999 ipv4: validate checksum_start before completing checksum 7h
Unknown CVE-2026-98432 ipv4: free inet_opt and ireq_opt after an RCU grace period 7h
Unknown CVE-2026-98424 wifi: cfg80211: undo netns switch if renaming the wiphy fails 1d
Unknown CVE-2026-98425 wifi: mac80211: don't warn when an IBSS has no channel to scan 1d
Unknown CVE-2026-98426 wifi: mwifiex: fix IRQ leak using wrong index in MSI-X error path 1d
Unknown CVE-2026-98427 net/sched: codel: bound the dropping loop per dequeue call 1d

Not in any source we poll

Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.

No CISA SSVC assessment.
No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
No exploit packet captures, log samples, or incident case IDs supplied.

Answered from this record

Text assembled only from the fields above — no additional claims.

What should defenders know first?

CVE-2026-46086 is "net: bridge: use a stable FDB dst snapshot in RCU readers", rated Medium. It affects Linux (Linux); versions are in the scope table. It is not in CISA KEV, which does not rule out exploitation. CVSS 5.5 describes technical severity. EPSS 0.13% estimates the probability of exploitation in 30 days; neither replaces your asset context. First verify whether exposed or business-critical assets run the affected versions, apply vendor fixes or mitigations, and preserve logs for review.

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