net: dsa: fix netdev_priv() dereference before check on non-DSA netdevice events

Description

In the Linux kernel, the following vulnerability has been resolved: net: dsa: fix netdev_priv() dereference before check on non-DSA netdevice events After the blamed commit, we started doing this dereference for every NETDEV_CHANGEUPPER and NETDEV_PRECHANGEUPPER event in the system. static inline struct dsa_port *dsa_user_to_port(const struct net_device *dev) { struct dsa_user_priv *p = netdev_priv(dev); return p->dp; } Which is obviously bogus, because not all net_devices have a netdev_priv() of type struct dsa_user_priv. But struct dsa_user_priv is fairly small, and p->dp means dereferencing 8 bytes starting with offset 16. Most drivers allocate that much private memory anyway, making our access not fault, and we discard the bogus data quickly afterwards, so this wasn't caught. But the dummy interface is somewhat special in that it calls alloc_netdev() with a priv size of 0. So every netdev_priv() dereference is invalid, and we get this when we emit a NETDEV_PRECHANGEUPPER event with a VLAN as its new upper: $ ip link add dummy1 type dummy $ ip link add link dummy1 name dummy1.100 type vlan id 100 [ 43.309174] ================================================================== [ 43.316456] BUG: KASAN: slab-out-of-bounds in dsa_user_prechangeupper+0x30/0xe8 [ 43.323835] Read of size 8 at addr ffff3f86481d2990 by task ip/374 [ 43.330058] [ 43.342436] Call trace: [ 43.366542] dsa_user_prechangeupper+0x30/0xe8 [ 43.371024] dsa_user_netdevice_event+0xb38/0xee8 [ 43.375768] notifier_call_chain+0xa4/0x210 [ 43.379985] raw_notifier_call_chain+0x24/0x38 [ 43.384464] __netdev_upper_dev_link+0x3ec/0x5d8 [ 43.389120] netdev_upper_dev_link+0x70/0xa8 [ 43.393424] register_vlan_dev+0x1bc/0x310 [ 43.397554] vlan_newlink+0x210/0x248 [ 43.401247] rtnl_newlink+0x9fc/0xe30 [ 43.404942] rtnetlink_rcv_msg+0x378/0x580 Avoid the kernel oops by dereferencing after the type check, as customary.

Timeline

Scores

EPSS (exploitation in 30 days)

0.24% · top 85% of all CVEs (11 Nov 2026)

CISA SSVC

Exploitation: none · Automatable: no · Technical impact: partial

The list uses the assigner's score when there is one, then CISA's, then NVD's: Medium 5.5.

Affected products

• Linux · Linux

  • affected 4c3f80d22b2eca911143ce656fa45c4699ff5bf4 – < 9e9953f5e4d6d11a9dad56fdee307bb923302809
  • affected 4c3f80d22b2eca911143ce656fa45c4699ff5bf4 – < 69a1e2d938dbbfcff0e064269adf60ad26dbb102
  • affected 4c3f80d22b2eca911143ce656fa45c4699ff5bf4 – < dbd909c20c11f0d29c0054d41e0d1f668a60e8c8
  • affected 4c3f80d22b2eca911143ce656fa45c4699ff5bf4 – < 844f104790bd69c2e4dbb9ee3eba46fde1fcea7b

• Linux · Linux

  • affected 6.1
  • unaffected < 6.1
  • unaffected 6.1.129 – ≤ 6.1.*
  • unaffected 6.6.55 – ≤ 6.6.*
  • unaffected 6.7.2 – ≤ 6.7.*
  • unaffected 6.8 – ≤ *

Sources

The same CVE in the primary databases and aggregators, to check against.

• CVE.org record (opens in a new tab)
• CVE List JSON (GitHub) (opens in a new tab)
• NVD (opens in a new tab)
• FIRST EPSS (opens in a new tab)
• EUVD EUVD-2024-23858 (opens in a new tab)
• OSV.dev (opens in a new tab)
• GitHub Advisories (opens in a new tab)
• CIRCL Vulnerability-Lookup (opens in a new tab)

Badge for a README or a ticket

[![CVE-2024-26596](https://cveledger.app/badge/CVE-2024-26596.svg)](https://cveledger.app/cve/CVE-2024-26596)

Record last updated 15 Oct 2026, 00:38 UTC.