# CVE-2021-47309: linux: In the Linux kernel, the following vulnerability has been resolved:  net: validate lwtstate->data before returning fr...

CVE-2021-47309 is fixed in linux on 1 platform, first by DEBIAN-CVE-2021-47309, released May 21, 2024. It is not reported as exploited. Patch Radar priority: High.

- Web page: https://patchblox.com/security/cve/CVE-2021-47309
- Priority: High
- CVSS: 7.1 (high)
- EPSS: 0.0025
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: May 21, 2024

## Description

In the Linux kernel, the following vulnerability has been resolved:  net: validate lwtstate->data before returning from skb_tunnel_info()  skb_tunnel_info() returns pointer of lwtstate->data as ip_tunnel_info type without validation. lwtstate->data can have various types such as mpls_iptunnel_encap, etc and these are not compatible. So skb_tunnel_info() should validate before returning that pointer.  Splat looks like: BUG: KASAN: slab-out-of-bounds in vxlan_get_route+0x418/0x4b0 [vxlan] Read of size 2 at addr ffff888106ec2698 by task ping/811  CPU: 1 PID: 811 Comm: ping Not tainted 5.13.0+ #1195 Call Trace:  dump_stack_lvl+0x56/0x7b  print_address_description.constprop.8.cold.13+0x13/0x2ee  ? vxlan_get_route+0x418/0x4b0 [vxlan]  ? vxlan_get_route+0x418/0x4b0 [vxlan]  kasan_report.cold.14+0x83/0xdf  ? vxlan_get_route+0x418/0x4b0 [vxlan]  vxlan_get_route+0x418/0x4b0 [vxlan]  [ ... ]  vxlan_xmit_one+0x148b/0x32b0 [vxlan]  [ ... ]  vxlan_xmit+0x25c5/0x4780 [vxlan]  [ ... ]  dev_hard_start_xmit+0x1ae/0x6e0  __dev_queue_xmit+0x1f39/0x31a0  [ ... ]  neigh_xmit+0x2f9/0x940  mpls_xmit+0x911/0x1600 [mpls_iptunnel]  lwtunnel_xmit+0x18f/0x450  ip_finish_output2+0x867/0x2040  [ ... ]

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | linux Debian 12.15 (bookworm) | 5.14.6-1 | [DEBIAN-CVE-2021-47309](https://patchblox.com/security/data/fix/linux/debian-cve-2021-47309.md) | May 21, 2024 |
| Linux | linux Debian 13.5 (trixie) | 5.14.6-1 | [DEBIAN-CVE-2021-47309](https://patchblox.com/security/data/fix/linux/debian-cve-2021-47309.md) | May 21, 2024 |
| Linux | linux Debian 14 | 5.14.6-1 | [DEBIAN-CVE-2021-47309](https://patchblox.com/security/data/fix/linux/debian-cve-2021-47309.md) | May 21, 2024 |

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