NVD / CVE Program· CNA Linux

CVE-2021-47162: tipc: skb_linearize the head skb when reassembling msgs

Noroxi assessment

Priority: Monitor (action score 22/100)

The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
Probability of exploitation in the next 30 days: 0.74% (FIRST EPSS); higher than 54.7% of all records.
Someone with local access to the system can trigger it. A low-privileged account is enough. No user action is required. No special conditions are required; it is repeatable.
Fixed version: Linux Linux 4.2, 4.3, 436d650d374329a591c30339a91fa5078052ed1e.
Severity is disputed: the assigning authority (CNA) scores it 9.8, NVD 5.5.

Low priority for now. Upgrade to Linux Linux 4.2, 4.3, 436d650d374329a591c30339a91fa5078052ed1e or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

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.

MediumCVSS 5.5 · v3.1—No exploit Fix available

Published: Mar 25, 2024
Updated: Aug 5, 2026
EPSS: 0.7% · 54th percentile
CWE: CWE-416

Report tools

JSON

Action score

Monitor

Low priority for now.

CVSS: 22 / 40 · 5.5 / 10
CISA KEV: 0 / 30 · Not listed
EPSS: 0 / 30 · 0.7%

CISA SSVC decision

Exploitation: none
Automatable: no
Technical impact: partial

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD: 5.5
CNA · Linux: 9.8; 4.3 point gap

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

Get told when this record changes

Not in KEV: no record of exploitation in the wild
No public exploit code on record
A fix has been released

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Noroxi analysis

What does it mean in your environment?

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

Vendor	Product	CPE
linux	linux kernel	cpe:2.3:o:linux:linux_kernel

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

linux linux kernel4.3 and later · before 4.4.271
linux linux kernel4.5 and later · before 4.9.271
linux linux kernel4.10 and later · before 4.14.235
linux linux kernel4.15 and later · before 4.19.193
linux linux kernel4.20 and later · before 5.4.124
linux linux kernel5.5 and later · before 5.10.42
linux linux kernel5.11 and later · before 5.12.9
linux linux kernel5.13

Versions reported by the vendor

Affected version ranges reported by the assigning authority (Linux). Independent of NVD's CPE analysis and usually ahead of it.

Linux Linux
- d45ed6c1ff20d3640a31f03816ca2d48fb7d6f22, c19282fd54a19e4651a4e67836cd842082546677, 4.3affected
- 45c8b7b175ceb2d542e0fe15247377bf3bce29ec and later · before b2c8d28c34b3070407cb1741f9ba3f15d0284b8baffected · git
- 45c8b7b175ceb2d542e0fe15247377bf3bce29ec and later · before 5489f30bb78ff0dafb4229a69632afc2ba20765caffected · git
- 45c8b7b175ceb2d542e0fe15247377bf3bce29ec and later · before 436d650d374329a591c30339a91fa5078052ed1eaffected · git
- 45c8b7b175ceb2d542e0fe15247377bf3bce29ec and later · before 4b1761898861117c97066aea6c58f68a7787f0bfaffected · git
- 45c8b7b175ceb2d542e0fe15247377bf3bce29ec and later · before 64d17ec9f1ded042c4b188d15734f33486ed9966affected · git
- 45c8b7b175ceb2d542e0fe15247377bf3bce29ec and later · before 6da24cfc83ba4f97ea44fc7ae9999a006101755caffected · git
- 45c8b7b175ceb2d542e0fe15247377bf3bce29ec and later · before ace300eecbccaa698e2b472843c74a5f33f7dce8affected · git
- 45c8b7b175ceb2d542e0fe15247377bf3bce29ec and later · before b7df21cf1b79ab7026f545e7bf837bd5750ac026affected · git
- 4.1.14 and later · before 4.2affected · semver

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

Ecosystem	Package	Affected range	Fix
Debian:12	linux	before 5.14.6-1	5.14.6-1
SUSE:Linux Enterprise High Availability Extension 12 SP5	kernel-default	before 4.12.14-122.219.1	4.12.14-122.219.1
SUSE:Linux Enterprise Live Patching 12 SP5	kernel-default	before 4.12.14-122.237.1	4.12.14-122.237.1
SUSE:Linux Enterprise Live Patching 12 SP5	kgraft-patch-SLE12-SP5_Update_57	before 1-8.3.1	1-8.3.1
SUSE:Linux Enterprise Live Patching 12 SP5	kgraft-patch-SLE12-SP5_Update_63	before 1-8.3.1	1-8.3.1
SUSE:Linux Enterprise Real Time 12 SP5	kernel-rt	before 4.12.14-10.188.1	4.12.14-10.188.1
SUSE:Linux Enterprise Real Time 12 SP5	kernel-rt_debug	before 4.12.14-10.188.1	4.12.14-10.188.1
SUSE:Linux Enterprise Real Time 12 SP5	kernel-source-rt	before 4.12.14-10.188.1	4.12.14-10.188.1
SUSE:Linux Enterprise Real Time 12 SP5	kernel-syms-rt	before 4.12.14-10.188.1	4.12.14-10.188.1
SUSE:Linux Enterprise Server 12 SP5	kernel-azure	before 4.12.14-16.188.1	4.12.14-16.188.1
SUSE:Linux Enterprise Server 12 SP5	kernel-source	before 4.12.14-122.219.1	4.12.14-122.219.1
SUSE:Linux Enterprise Server 12 SP5	kernel-source-azure	before 4.12.14-16.188.1	4.12.14-16.188.1
SUSE:Linux Enterprise Server 12 SP5	kernel-syms	before 4.12.14-122.219.1	4.12.14-122.219.1
SUSE:Linux Enterprise Server 12 SP5	kernel-syms-azure	before 4.12.14-16.188.1	4.12.14-16.188.1
SUSE:Linux Enterprise Server 12 SP5-LTSS	kernel-source	before 4.12.14-122.237.1	4.12.14-122.237.1
SUSE:Linux Enterprise Server 12 SP5-LTSS	kernel-syms	before 4.12.14-122.237.1	4.12.14-122.237.1
SUSE:Linux Enterprise Software Development Kit 12 SP5	kernel-docs	before 4.12.14-122.219.1	4.12.14-122.219.1
SUSE:Linux Enterprise Software Development Kit 12 SP5	kernel-obs-build	before 4.12.14-122.219.1	4.12.14-122.219.1

Same product

linux: all records

Other highest-scoring records for the same primary product.

CVE-2026-31431crypto: algif_aead - Revert to operating out-of-placeKEV
90Now
CVE-2022-0847A flaw was found in the way the "flags" member of the new pipe buffer structure was lacking proper initialization in copy_page_to_iter_pipe KEV
89Now
CVE-2021-22555Heap Out-Of-Bounds Write in Netfilter IP6T_SO_SET_REPLACEKEV
85Now

Published before and after this one in the same product

← EarlierCVE-2021-47160Mar 25, 2024 · net: dsa: mt7530: fix VLAN traffic leaks
28Monitor
← EarlierCVE-2021-47161Mar 25, 2024 · spi: spi-fsl-dspi: Fix a resource leak in an error handling path
22Monitor
Later →CVE-2021-47163Mar 25, 2024 · tipc: wait and exit until all work queues are done
22Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / package	Fixed version	Source
Linux Linux	4.2	Vendor (CNA)
Linux Linux	4.3	Vendor (CNA)
Linux Linux	436d650d374329a591c30339a91fa5078052ed1e	Vendor (CNA)
Linux Linux	4b1761898861117c97066aea6c58f68a7787f0bf	Vendor (CNA)
Linux Linux	5489f30bb78ff0dafb4229a69632afc2ba20765c	Vendor (CNA)
Linux Linux	64d17ec9f1ded042c4b188d15734f33486ed9966	Vendor (CNA)
Linux Linux	6da24cfc83ba4f97ea44fc7ae9999a006101755c	Vendor (CNA)
Linux Linux	ace300eecbccaa698e2b472843c74a5f33f7dce8	Vendor (CNA)
Linux Linux	b2c8d28c34b3070407cb1741f9ba3f15d0284b8b	Vendor (CNA)
Linux Linux	b7df21cf1b79ab7026f545e7bf837bd5750ac026	Vendor (CNA)
debian:linux	5.14.6-1 · Debian:12	Package registry (OSV)
suse:kernel-azure	4.12.14-16.188.1 · SUSE:Linux Enterprise Server 12 SP5	Package registry (OSV)
suse:kernel-default	4.12.14-122.219.1 · SUSE:Linux Enterprise High Availability Extension 12 SP5	Package registry (OSV)
suse:kernel-docs	4.12.14-122.219.1 · SUSE:Linux Enterprise Software Development Kit 12 SP5	Package registry (OSV)
suse:kernel-obs-build	4.12.14-122.219.1 · SUSE:Linux Enterprise Software Development Kit 12 SP5	Package registry (OSV)
suse:kernel-rt	4.12.14-10.188.1 · SUSE:Linux Enterprise Real Time 12 SP5	Package registry (OSV)
suse:kernel-rt_debug	4.12.14-10.188.1 · SUSE:Linux Enterprise Real Time 12 SP5	Package registry (OSV)
suse:kernel-source	4.12.14-122.219.1 · SUSE:Linux Enterprise Server 12 SP5	Package registry (OSV)
suse:kernel-source-azure	4.12.14-16.188.1 · SUSE:Linux Enterprise Server 12 SP5	Package registry (OSV)
suse:kernel-source-rt	4.12.14-10.188.1 · SUSE:Linux Enterprise Real Time 12 SP5	Package registry (OSV)
suse:kernel-syms-azure	4.12.14-16.188.1 · SUSE:Linux Enterprise Server 12 SP5	Package registry (OSV)
suse:kernel-syms-rt	4.12.14-10.188.1 · SUSE:Linux Enterprise Real Time 12 SP5	Package registry (OSV)
suse:kgraft-patch-SLE12-SP5_Update_57	1-8.3.1 · SUSE:Linux Enterprise Live Patching 12 SP5	Package registry (OSV)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

No history yet (it accumulates with the daily EPSS job).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

No commit or PR link among the references.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

No nightly-computed relations.

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

Technical details

Attack conditions

Someone with local access to the system can trigger it.
A low-privileged account is enough.
No user action is required.
No special conditions are required; it is repeatable.

If successful

Confidentiality: none
Integrity: none
Availability: high · the service can be disrupted

Attack vector: Local
Attack complexity: Low
Privileges required: Low
User interaction: None
Scope: Unchanged
Confidentiality impact: None
Integrity impact: None
Availability impact: High

Weakness class (CWE)

CWE-416 · Use After Free

CVSS vector

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

nvd-primary

Root cause

After a memory region is freed, another reference pointing to it is still used. By then, the same region may have been allocated for different data.

The bug in code

The whole CWE-416 class

A representative example of this vulnerability class. Not the vendor's source code; it shows the faulty pattern and its fix.

Vulnerable

1free(dev->buf);
2/* ... another thread is still running ... */
3process(dev->buf);

Fixed

1lock(&dev->lock);
2free(dev->buf);
3dev->buf = NULL;
4unlock(&dev->lock);

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

MITRE has no CAPEC/ATT&CK mapping for this CWE.

Change log

Fix✗ → ✓Sep 28, 2026, 10:10 PM UTC

For records you follow, these changes also arrive as notifications. →

References

git.kernel.org/stable/c/436d650d374329a591c30339a91fa5078052ed1e

Show all references (7 more)

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records