VulnerabilityPublished 27 May 2026Updated 6 Nov 2026

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

Affects Linux kernelSource CVE Database V5

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Not known to be exploited · fixed in df4601653201de21b487c3e7fffd464790cab808 : update Linux kernel when convenient.

Data as of 6 Nov 2026, 16:34 UTC

Severity

Unrated

Rated by Threat Radar · No CVSS score from NVD or the CNA

Thin evidence

One scorer or none

Exploitation: No evidence of active exploitation and no public proof of concept
Automatable: Attackers cannot reliably automate steps 1–4 of the kill chain
Technical impact: Limited control over the software or limited information exposure

CISA SSVC assessment, 2026-11-06.

Patch

Available – fixed in df4601653201de21b487c3e7fffd464790cab808, c502fa9f094cb03d1d1685c71e2105ab359bc2b8, a6ae4511c07b91f597e461406c6330f0d4ff810e +5

Exploitation evidence

Disclosed: evidence found.
CVE published 27 May 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 6 Nov 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Upgrade to a fixed release listed under Affected software.

Affected software

Product	Affected	Fixed in
LinuxLinux	Affected ≥ 960b589f86c74ce582922fcb996103271081f4de, < df4601653201de21b487c3e7fffd464790cab808	Fixed in df4601653201de21b487c3e7fffd464790cab808
LinuxLinux	Affected ≥ 960b589f86c74ce582922fcb996103271081f4de, < c502fa9f094cb03d1d1685c71e2105ab359bc2b8	Fixed in c502fa9f094cb03d1d1685c71e2105ab359bc2b8
LinuxLinux	Affected ≥ 960b589f86c74ce582922fcb996103271081f4de, < a6ae4511c07b91f597e461406c6330f0d4ff810e	Fixed in a6ae4511c07b91f597e461406c6330f0d4ff810e
LinuxLinux	Affected ≥ 960b589f86c74ce582922fcb996103271081f4de, < 5424e678f9b304e148cf5dcc047cffc7a56a3bb5	Fixed in 5424e678f9b304e148cf5dcc047cffc7a56a3bb5
LinuxLinux	Affected ≥ 960b589f86c74ce582922fcb996103271081f4de, < 1406c4e0ed1eaf8a29801ab1163d00fb7ee4359a	Fixed in 1406c4e0ed1eaf8a29801ab1163d00fb7ee4359a
LinuxLinux	Affected ≥ 960b589f86c74ce582922fcb996103271081f4de, < 81af4137a30c4c2dc694dea8cacb180bd66000ef	Fixed in 81af4137a30c4c2dc694dea8cacb180bd66000ef

Description

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.

References

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