CVE-2021-47162
In the Linux kernel, the following vulnerability has been resolved: tipc: skb_linearize the head skb when reassembling msgs It's not a good idea to append the frag skb to a skb's frag_list if the frag_list already has skbs from elsewhere, such as this…
Does this matter?
Lower severity and a low EPSS score (0.74%). Track it; it rarely justifies an emergency change on its own.
Description
In the Linux kernel, the following vulnerability has been resolved: tipc: skb_linearize the head skb when reassembling msgs It's not a good idea to append the frag skb to a skb's frag_list if the frag_list already has skbs from elsewhere, such as this skb was created by pskb_copy() where the frag_list was cloned (all the skbs in it were skb_get'ed) and shared by multiple skbs. However, the new appended frag skb should have been only seen by the current skb. Otherwise, it will cause use after free crashes as this appended frag skb are seen by multiple skbs but it only got skb_get called once. The same thing happens with a skb updated by pskb_may_pull() with a skb_cloned skb. Li Shuang has reported quite a few crashes caused by this when doing testing over macvlan devices: [] kernel BUG at net/core/skbuff.c:1970! [] Call Trace: [] skb_clone+0x4d/0xb0 [] macvlan_broadcast+0xd8/0x160 [macvlan] [] macvlan_process_broadcast+0x148/0x150 [macvlan] [] process_one_work+0x1a7/0x360 [] worker_thread+0x30/0x390 [] kernel BUG at mm/usercopy.c:102! [] Call Trace: [] __check_heap_object+0xd3/0x100 [] __check_object_size+0xff/0x16b [] simple_copy_to_iter+0x1c/0x30 [] __skb_datagram_iter+0x7d/0x310 [] __skb_datagram_iter+0x2a5/0x310 [] skb_copy_datagram_iter+0x3b/0x90 [] tipc_recvmsg+0x14a/0x3a0 [tipc] [] ____sys_recvmsg+0x91/0x150 [] ___sys_recvmsg+0x7b/0xc0 [] kernel BUG at mm/slub.c:305! [] Call Trace: [] <IRQ> [] kmem_cache_free+0x3ff/0x400 [] __netif_receive_skb_core+0x12c/0xc40 [] ? kmem_cache_alloc+0x12e/0x270 [] netif_receive_skb_internal+0x3d/0xb0 [] ? get_rx_page_info+0x8e/0xa0 [be2net] [] be_poll+0x6ef/0xd00 [be2net] [] ? irq_exit+0x4f/0x100 [] net_rx_action+0x149/0x3b0 ... This patch is to fix it by linearizing the head skb if it has frag_list set in tipc_buf_append(). Note that we choose to do this before calling skb_unshare(), as __skb_linearize() will avoid skb_copy(). Also, we can not just drop the frag_list either as the early time.
- CVSS 3.1
- 5.5 MEDIUMCVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
- EPSS
- 0.74% probability · 54th percentile
- Public exploits
- None in Exploit-DB
- CISA KEV
- Not listed
- Weakness
- CWE-416
- Affected
- linux/linux kernel
- Source
- 416baaa9-dc9f-4396-8d5f-8c081fb06d67
EPSS 0.7% since 26 October 2026; no change recorded yet. Points are recorded when the score first appears and whenever it moves by a percentage point or more.
References
- https://git.kernel.org/stable/c/436d650d374329a591c30339a91fa5078052ed1ePatch
- https://git.kernel.org/stable/c/4b1761898861117c97066aea6c58f68a7787f0bfPatch
- https://git.kernel.org/stable/c/5489f30bb78ff0dafb4229a69632afc2ba20765cPatch
- https://git.kernel.org/stable/c/64d17ec9f1ded042c4b188d15734f33486ed9966Patch
- https://git.kernel.org/stable/c/6da24cfc83ba4f97ea44fc7ae9999a006101755cPatch
- https://git.kernel.org/stable/c/ace300eecbccaa698e2b472843c74a5f33f7dce8Patch
- https://git.kernel.org/stable/c/b2c8d28c34b3070407cb1741f9ba3f15d0284b8bPatch
- https://git.kernel.org/stable/c/b7df21cf1b79ab7026f545e7bf837bd5750ac026Patch
- https://git.kernel.org/stable/c/436d650d374329a591c30339a91fa5078052ed1ePatch
- https://git.kernel.org/stable/c/4b1761898861117c97066aea6c58f68a7787f0bfPatch
- https://git.kernel.org/stable/c/5489f30bb78ff0dafb4229a69632afc2ba20765cPatch
- https://git.kernel.org/stable/c/64d17ec9f1ded042c4b188d15734f33486ed9966Patch
- https://git.kernel.org/stable/c/6da24cfc83ba4f97ea44fc7ae9999a006101755cPatch
- https://git.kernel.org/stable/c/ace300eecbccaa698e2b472843c74a5f33f7dce8Patch
- https://git.kernel.org/stable/c/b2c8d28c34b3070407cb1741f9ba3f15d0284b8bPatch
- https://git.kernel.org/stable/c/b7df21cf1b79ab7026f545e7bf837bd5750ac026Patch
Source: NVD record, EPSS from FIRST.org, KEV from CISA, exploits from Exploit-DB. Refreshed daily. Download this record as JSON.