NVD / CVE Program· CNA Linux

CVE-2021-47013: net:emac/emac-mac: Fix a use after free in emac_mac_tx_buf_send

Noroxi assessment

Priority: Monitor (action score 31/100)

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: 0.79% (FIRST EPSS); higher than 56.2% 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 16d8c44be52e3650917736d45f5904384a9da834, 55fcdd1258faaecca74b91b88cc0921f9edd775d, 6d72e7c767acbbdd44ebc7d89c6690b405b32b57.
Severity is disputed: the assigning authority (CNA) scores it 9.8, NVD 7.8.
Mentioned 1 time in Turkish national cyber security advisories (siberguvenlik.gov.tr).

Low priority for now. Upgrade to Linux Linux 16d8c44be52e3650917736d45f5904384a9da834, 55fcdd1258faaecca74b91b88cc0921f9edd775d, 6d72e7c767acbbdd44ebc7d89c6690b405b32b57 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: net:emac/emac-mac: Fix a use after free in emac_mac_tx_buf_send In emac_mac_tx_buf_send, it calls emac_tx_fill_tpd(..,skb,..). If some error happens in emac_tx_fill_tpd(), the skb will be freed via dev_kfree_skb(skb) in error branch of emac_tx_fill_tpd(). But the freed skb is still used via skb->len by netdev_sent_queue(,skb->len). As i observed that emac_tx_fill_tpd() haven't modified the value of skb->len, thus my patch assigns skb->len to 'len' before the possible free and use 'len' instead of skb->len later.

HighCVSS 7.8 · v3.1—No exploit Fix available

Memory safety

Published: Feb 28, 2024
Updated: Aug 5, 2026
EPSS: 0.7% · 56th percentile
CWE: CWE-416

Report tools

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Action score

Monitor

Low priority for now.

CVSS: 31 / 40 · 7.8 / 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: 7.8
CNA · Linux: 9.8; 2.0 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?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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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 kernel4.9 and later · before 4.9.269
linux linux kernel4.10 and later · before 4.14.233
linux linux kernel4.15 and later · before 4.19.191
linux linux kernel4.20 and later · before 5.4.119
linux linux kernel5.5 and later · before 5.10.37
linux linux kernel5.11 and later · before 5.11.21
linux linux kernel5.12 and later · before 5.12.4

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
- 4.9affected
- b9b17debc69d27cd55e21ee51a5ba7fc50a426cf and later · before c7f75d11fe72913d2619f97b2334b083cd7bb955affected · git
- b9b17debc69d27cd55e21ee51a5ba7fc50a426cf and later · before dc1b438a35773d030be0ee80d9c635c3e558a322affected · git
- b9b17debc69d27cd55e21ee51a5ba7fc50a426cf and later · before 16d8c44be52e3650917736d45f5904384a9da834affected · git
- b9b17debc69d27cd55e21ee51a5ba7fc50a426cf and later · before 55fcdd1258faaecca74b91b88cc0921f9edd775daffected · git
- b9b17debc69d27cd55e21ee51a5ba7fc50a426cf and later · before 9dc373f74097edd0e35f3393d6248eda8d1ba99daffected · git
- b9b17debc69d27cd55e21ee51a5ba7fc50a426cf and later · before 8c06f34785068b87e2b560534c77c163d6c6dca7affected · git
- b9b17debc69d27cd55e21ee51a5ba7fc50a426cf and later · before e407495ba6788a67d1bd41714158c079e340879baffected · git
- b9b17debc69d27cd55e21ee51a5ba7fc50a426cf and later · before 6d72e7c767acbbdd44ebc7d89c6690b405b32b57affected · git
- before 4.9not affected · semver

Package-level exposure

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

Ecosystem	Package	Affected range	Fix
AlmaLinux:8	bpftool	before 4.18.0-553.5.1.el8_10	4.18.0-553.5.1.el8_10
AlmaLinux:8	kernel	before 4.18.0-553.5.1.el8_10	4.18.0-553.5.1.el8_10
AlmaLinux:8	kernel-abi-stablelists	before 4.18.0-553.5.1.el8_10	4.18.0-553.5.1.el8_10
AlmaLinux:8	kernel-core	before 4.18.0-553.5.1.el8_10	4.18.0-553.5.1.el8_10
AlmaLinux:8	kernel-cross-headers	before 4.18.0-553.5.1.el8_10	4.18.0-553.5.1.el8_10
AlmaLinux:8	kernel-debug	before 4.18.0-553.5.1.el8_10	4.18.0-553.5.1.el8_10
AlmaLinux:8	kernel-debug-core	before 4.18.0-553.5.1.el8_10	4.18.0-553.5.1.el8_10
AlmaLinux:8	kernel-debug-devel	before 4.18.0-553.5.1.el8_10	4.18.0-553.5.1.el8_10
AlmaLinux:8	kernel-debug-modules	before 4.18.0-553.5.1.el8_10	4.18.0-553.5.1.el8_10
AlmaLinux:8	kernel-debug-modules-extra	before 4.18.0-553.5.1.el8_10	4.18.0-553.5.1.el8_10
AlmaLinux:8	kernel-devel	before 4.18.0-553.5.1.el8_10	4.18.0-553.5.1.el8_10
AlmaLinux:8	kernel-doc	before 4.18.0-553.5.1.el8_10	4.18.0-553.5.1.el8_10
AlmaLinux:8	kernel-headers	before 4.18.0-553.5.1.el8_10	4.18.0-553.5.1.el8_10
AlmaLinux:8	kernel-modules	before 4.18.0-553.5.1.el8_10	4.18.0-553.5.1.el8_10
AlmaLinux:8	kernel-modules-extra	before 4.18.0-553.5.1.el8_10	4.18.0-553.5.1.el8_10
AlmaLinux:8	kernel-rt	before 4.18.0-553.5.1.rt7.346.el8_10	4.18.0-553.5.1.rt7.346.el8_10
AlmaLinux:8	kernel-rt-core	before 4.18.0-553.5.1.rt7.346.el8_10	4.18.0-553.5.1.rt7.346.el8_10
AlmaLinux:8	kernel-rt-debug	before 4.18.0-553.5.1.rt7.346.el8_10	4.18.0-553.5.1.rt7.346.el8_10
AlmaLinux:8	kernel-rt-debug-core	before 4.18.0-553.5.1.rt7.346.el8_10	4.18.0-553.5.1.rt7.346.el8_10
AlmaLinux:8	kernel-rt-debug-devel	before 4.18.0-553.5.1.rt7.346.el8_10	4.18.0-553.5.1.rt7.346.el8_10
AlmaLinux:8	kernel-rt-debug-kvm	before 4.18.0-553.5.1.rt7.346.el8_10	4.18.0-553.5.1.rt7.346.el8_10
AlmaLinux:8	kernel-rt-debug-modules	before 4.18.0-553.5.1.rt7.346.el8_10	4.18.0-553.5.1.rt7.346.el8_10
AlmaLinux:8	kernel-rt-debug-modules-extra	before 4.18.0-553.5.1.rt7.346.el8_10	4.18.0-553.5.1.rt7.346.el8_10
AlmaLinux:8	kernel-rt-devel	before 4.18.0-553.5.1.rt7.346.el8_10	4.18.0-553.5.1.rt7.346.el8_10

+96

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-2021-47011Feb 28, 2024 · mm: memcontrol: slab: fix obtain a reference to a freeing memcg
22Monitor
← EarlierCVE-2021-47012Feb 28, 2024 · RDMA/siw: Fix a use after free in siw_alloc_mr
31Monitor
Later →CVE-2021-47014Feb 28, 2024 · net/sched: act_ct: fix wild memory access when clearing fragments
31Monitor

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	16d8c44be52e3650917736d45f5904384a9da834	Vendor (CNA)
Linux Linux	55fcdd1258faaecca74b91b88cc0921f9edd775d	Vendor (CNA)
Linux Linux	6d72e7c767acbbdd44ebc7d89c6690b405b32b57	Vendor (CNA)
Linux Linux	8c06f34785068b87e2b560534c77c163d6c6dca7	Vendor (CNA)
Linux Linux	9dc373f74097edd0e35f3393d6248eda8d1ba99d	Vendor (CNA)
Linux Linux	c7f75d11fe72913d2619f97b2334b083cd7bb955	Vendor (CNA)
Linux Linux	dc1b438a35773d030be0ee80d9c635c3e558a322	Vendor (CNA)
Linux Linux	e407495ba6788a67d1bd41714158c079e340879b	Vendor (CNA)
almalinux:bpftool	4.18.0-553.5.1.el8_10 · AlmaLinux:8	Package registry (OSV)
almalinux:kernel	4.18.0-553.5.1.el8_10 · AlmaLinux:8	Package registry (OSV)
almalinux:kernel-abi-stablelists	4.18.0-553.5.1.el8_10 · AlmaLinux:8	Package registry (OSV)
almalinux:kernel-core	4.18.0-553.5.1.el8_10 · AlmaLinux:8	Package registry (OSV)
almalinux:kernel-cross-headers	4.18.0-553.5.1.el8_10 · AlmaLinux:8	Package registry (OSV)
almalinux:kernel-debug	4.18.0-553.5.1.el8_10 · AlmaLinux:8	Package registry (OSV)
almalinux:kernel-debug-core	4.18.0-553.5.1.el8_10 · AlmaLinux:8	Package registry (OSV)
almalinux:kernel-debug-devel	4.18.0-553.5.1.el8_10 · AlmaLinux:8	Package registry (OSV)
almalinux:kernel-debug-modules	4.18.0-553.5.1.el8_10 · AlmaLinux:8	Package registry (OSV)
almalinux:kernel-debug-modules-extra	4.18.0-553.5.1.el8_10 · AlmaLinux:8	Package registry (OSV)
almalinux:kernel-devel	4.18.0-553.5.1.el8_10 · AlmaLinux:8	Package registry (OSV)
almalinux:kernel-doc	4.18.0-553.5.1.el8_10 · AlmaLinux:8	Package registry (OSV)
debian:linux	5.10.38-1 · Debian:12	Package registry (OSV)
red hat:bpftool	0:4.18.0-372.105.1.el8_6 · Red Hat:rhel_eus:8.6::baseos	Package registry (OSV)
red hat:bpftool-debuginfo	0:4.18.0-372.105.1.el8_6 · Red Hat:rhev_hypervisor:4.4::el8	Package registry (OSV)
red hat:kernel	0:4.18.0-372.105.1.el8_6 · Red Hat:rhel_eus:8.6::baseos	Package registry (OSV)
red hat:kernel-abi-stablelists	0:4.18.0-372.105.1.el8_6 · Red Hat:rhel_eus:8.6::baseos	Package registry (OSV)
red hat:kernel-debug-debuginfo	0:4.18.0-372.105.1.el8_6 · Red Hat:rhev_hypervisor:4.4::el8	Package registry (OSV)
red hat:kernel-debuginfo	0:4.18.0-372.105.1.el8_6 · Red Hat:rhev_hypervisor:4.4::el8	Package registry (OSV)
red hat:kernel-debuginfo-common-x86_64	0:4.18.0-372.105.1.el8_6 · Red Hat:rhev_hypervisor:4.4::el8	Package registry (OSV)
red hat:kernel-devel	0:4.18.0-372.105.1.el8_6 · Red Hat:rhev_hypervisor:4.4::el8	Package registry (OSV)
red hat:kernel-tools-debuginfo	0:4.18.0-372.105.1.el8_6 · Red Hat:rhev_hypervisor:4.4::el8	Package registry (OSV)

+17

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).

National notice (Türkiye Cybersecurity Directorate / USOM)

Official security notices citing this record; remediation advice is on the agency's page.

TR-24-0145 · Feb 29, 2024(Linux Kernel Güncellemesi)

All national notices →

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: high · data can be read
Integrity: high · data or configuration can be modified
Availability: high · the service can be disrupted

Attack vector: Local
Attack complexity: Low
Privileges required: Low
User interaction: None
Scope: Unchanged
Confidentiality impact: High
Integrity impact: High
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:H/I:H/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, 10:09 PM UTC

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

References

git.kernel.org/stable/c/16d8c44be52e3650917736d45f5904384a9da834

Show all references (7 more)

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

All records