CVE-2026-46086: net: bridge: use a stable FDB dst snapshot in RCU readers
Vulnerability summary
CVE-2026-46086 is a medium (CVSS 5.5) NULL Pointer Dereference vulnerability in linux. EPSS estimates a 0.13% chance of exploitation in the next 30 days, higher than 2.5% of scored vulnerabilities.
Not severe (CVSS 5.5, local access); no exploitation reported by the 5 checked sources
Source freshness unavailable
How is this decided?Advisory lineage
Upstream 0 · Downstream 44 · Related 40Timeline
- 27-05-2026PublishedVulnerability first disclosed.
- 15-10-2026Last modifiedVulnerability information updated.
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.
CVSS metrics
3 scores · 3 sources · 1 version- OSV · UbuntuEcosystem advisory · calculated5.5MediumCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
- OSV · DebianEcosystem advisory · calculated5.5MediumCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
EPSS trend
Probability
0.13%
Chance of exploitation in the next 30 days
Percentile
3%
Versus all other CVEs
30-day change
Decrease -0.04 pp
From 0.17% on 04-10-2026
Known exploited
Compare KEV catalogs
CISA KEVNot in the CISA KEV catalog.
ENISA CNWNot in the ENISA CNW catalog.
CIRCLNot in the CIRCL catalog.
Public exploits
0 foundNo public exploits indexed.
Weaknesses
CWE · root causeAffected systems
Known conditions: local access, low-privilege account, no user interaction (CVSS vector). Other conditions: not stated in public data.
Ubuntu159 products
- linuxAll versions (No fix recorded) | < 5.15.0-198.208 | < 6.8.0-136.136 | < 7.0.0-27.27
- linux-allwinner-5.19All versions (No fix recorded)
- linux-awsAll versions (No fix recorded) | < 5.15.0-1117.124 | < 6.8.0-1061.64 | < 7.0.0-1008.8
- linux-aws-5.0All versions (No fix recorded)
- linux-aws-5.11All versions (No fix recorded)
Linux2 products
- linux≥ 960b589f86c74ce582922fcb996103271081f4de, < c502fa9f094cb03d1d1685c71e2105ab359bc2b8 | ≥ 960b589f86c74ce582922fcb996103271081f4de, < a6ae4511c07b91f597e461406c6330f0d4ff810e | ≥ 960b589f86c74ce582922fcb996103271081f4de, < 1406c4e0ed1eaf8a29801ab1163d00fb7ee4359a | ≥ 960b589f86c74ce582922fcb996103271081f4de, < 0b9e4bbfb7c949151e3acd44ed4aa33614d2e110 | ≥ 960b589f86c74ce582922fcb996103271081f4de, < 81af4137a30c4c2dc694dea8cacb180bd66000ef | ≥ 960b589f86c74ce582922fcb996103271081f4de, < 5424e678f9b304e148cf5dcc047cffc7a56a3bb5 | ≥ 960b589f86c74ce582922fcb996103271081f4de, < 9a2d9d4e657b23dc21f24cf139e3aeff0b61341f | ≥ 960b589f86c74ce582922fcb996103271081f4de, < df4601653201de21b487c3e7fffd464790cab808 | 3.14
- linux_kernel≥ 3.14.1, < 5.10.259 | ≥ 5.11, < 5.15.210 | ≥ 5.16, < 6.1.176 | ≥ 6.2, < 6.6.140 | ≥ 6.7, < 6.12.86 | ≥ 6.13, < 6.18.27 | ≥ 6.19, < 7.0.4 | 3.14 | 3.14:rc3 | 3.14:rc4 | 3.14:rc5 | 3.14:rc6 | 3.14:rc7 | 3.14:rc8
Debian1 product
- linux< 6.1.176-1 | < 6.12.86-1 | < 7.0.4-1
3 vendors · 162 products
