NVD / CVE Program· CNA Linux

CVE-2021-47131: net/tls: Fix use-after-free after the TLS device goes down and up

HighCVSS 7.8 · v3.1—No exploit Fix available

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: 0.75% (FIRST EPSS); higher than 55.4% 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 0f1e6fe66977a864fe850522316f713d7b926fd9, c55dcdd435aa6c6ad6ccac0a4c636d010ee367a4, f1d4184f128dede82a59a841658ed40d4e6d3aa2.
Mentioned 2 times in Turkish national cyber security advisories (siberguvenlik.gov.tr).

Low priority for now. Upgrade to Linux Linux 0f1e6fe66977a864fe850522316f713d7b926fd9, c55dcdd435aa6c6ad6ccac0a4c636d010ee367a4, f1d4184f128dede82a59a841658ed40d4e6d3aa2 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/tls: Fix use-after-free after the TLS device goes down and up When a netdev with active TLS offload goes down, tls_device_down is called to stop the offload and tear down the TLS context. However, the socket stays alive, and it still points to the TLS context, which is now deallocated. If a netdev goes up, while the connection is still active, and the data flow resumes after a number of TCP retransmissions, it will lead to a use-after-free of the TLS context. This commit addresses this bug by keeping the context alive until its normal destruction, and implements the necessary fallbacks, so that the connection can resume in software (non-offloaded) kTLS mode. On the TX side tls_sw_fallback is used to encrypt all packets. The RX side already has all the necessary fallbacks, because receiving non-decrypted packets is supported. The thing needed on the RX side is to block resync requests, which are normally produced after receiving non-decrypted packets. The necessary synchronization is implemented for a graceful teardown: first the fallbacks are deployed, then the driver resources are released (it used to be possible to have a tls_dev_resync after tls_dev_del). A new flag called TLS_RX_DEV_DEGRADED is added to indicate the fallback mode. It's used to skip the RX resync logic completely, as it becomes useless, and some objects may be released (for example, resync_async, which is allocated and freed by the driver).

Memory safety

Published: Mar 15, 2024
Updated: Aug 5, 2026
EPSS: 0.7% · 55th percentile
CWE: CWE-416

Report tools

JSON

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: 8.1; 0.3 point gap

CVSS:3.1/AV:N/AC:H/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

If any of these changes, we'll tell you in the daily email digest.

Is your version affected? Check it

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

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
- 4.18affected
- e8f69799810c32dd40c6724d829eccc70baad07f and later · before f1d4184f128dede82a59a841658ed40d4e6d3aa2affected · git
- e8f69799810c32dd40c6724d829eccc70baad07f and later · before 0f1e6fe66977a864fe850522316f713d7b926fd9affected · git
- e8f69799810c32dd40c6724d829eccc70baad07f and later · before c55dcdd435aa6c6ad6ccac0a4c636d010ee367a4affected · git
- before 4.18not affected · semver
- 5.10.43 and later · up to and including 5.10.*not affected · semver
- 5.12.10 and later · up to and including 5.12.*not affected · semver
- 5.13 and laternot affected · original_commit_for_fix

Affected versions

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

linux linux kernel4.18 and later · before 5.10.43
linux linux kernel5.11 and later · before 5.12.10
linux linux kernel5.13

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 5.10.46-1	5.10.46-1
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 High Performance Computing 15 SP2-LTSS	kernel-default-base	before 5.3.18-150200.24.191.1.150200.9.97.1	5.3.18-150200.24.191.1.150200.9.97.1
SUSE:Linux Enterprise High Performance Computing 15 SP2-LTSS	kernel-docs	before 5.3.18-150200.24.191.1	5.3.18-150200.24.191.1
SUSE:Linux Enterprise High Performance Computing 15 SP2-LTSS	kernel-obs-build	before 5.3.18-150200.24.191.1	5.3.18-150200.24.191.1
SUSE:Linux Enterprise High Performance Computing 15 SP2-LTSS	kernel-preempt	before 5.3.18-150200.24.191.1	5.3.18-150200.24.191.1
SUSE:Linux Enterprise High Performance Computing 15 SP2-LTSS	kernel-source	before 5.3.18-150200.24.191.1	5.3.18-150200.24.191.1
SUSE:Linux Enterprise High Performance Computing 15 SP2-LTSS	kernel-syms	before 5.3.18-150200.24.191.1	5.3.18-150200.24.191.1
SUSE:Linux Enterprise High Performance Computing 15 SP3-LTSS	kernel-64kb	before 5.3.18-150300.59.161.1	5.3.18-150300.59.161.1
SUSE:Linux Enterprise High Performance Computing 15 SP3-LTSS	kernel-default-base	before 5.3.18-150300.59.161.1.150300.18.94.1	5.3.18-150300.59.161.1.150300.18.94.1
SUSE:Linux Enterprise High Performance Computing 15 SP3-LTSS	kernel-docs	before 5.3.18-150300.59.161.2	5.3.18-150300.59.161.2
SUSE:Linux Enterprise High Performance Computing 15 SP3-LTSS	kernel-obs-build	before 5.3.18-150300.59.161.1	5.3.18-150300.59.161.1
SUSE:Linux Enterprise High Performance Computing 15 SP3-LTSS	kernel-preempt	before 5.3.18-150300.59.161.1	5.3.18-150300.59.161.1
SUSE:Linux Enterprise High Performance Computing 15 SP3-LTSS	kernel-source	before 5.3.18-150300.59.161.1	5.3.18-150300.59.161.1
SUSE:Linux Enterprise High Performance Computing 15 SP3-LTSS	kernel-syms	before 5.3.18-150300.59.161.1	5.3.18-150300.59.161.1
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 15 SP2	kernel-default	before 5.3.18-150200.24.191.1	5.3.18-150200.24.191.1
SUSE:Linux Enterprise Live Patching 15 SP2	kernel-livepatch-SLE15-SP2_Update_48	before 1-150200.5.3.1	1-150200.5.3.1
SUSE:Linux Enterprise Live Patching 15 SP3	kernel-default	before 5.3.18-150300.59.161.1	5.3.18-150300.59.161.1
SUSE:Linux Enterprise Live Patching 15 SP3	kernel-livepatch-SLE15-SP3_Update_44	before 1-150300.7.3.1	1-150300.7.3.1
SUSE:Linux Enterprise Micro 5.1	kernel-rt	before 5.3.18-150300.169.1	5.3.18-150300.169.1
SUSE:Linux Enterprise Micro 5.1	kernel-source-rt	before 5.3.18-150300.169.1	5.3.18-150300.169.1
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

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-2021-47129Mar 15, 2024 · netfilter: nft_ct: skip expectations for confirmed conntrack
31Monitor
← EarlierCVE-2021-47130Mar 15, 2024 · nvmet: fix freeing unallocated p2pmem
30Monitor
Later →CVE-2021-47132Mar 15, 2024 · mptcp: fix sk_forward_memory corruption on retransmission
28Monitor

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	0f1e6fe66977a864fe850522316f713d7b926fd9	Vendor (CNA)
Linux Linux	c55dcdd435aa6c6ad6ccac0a4c636d010ee367a4	Vendor (CNA)
Linux Linux	f1d4184f128dede82a59a841658ed40d4e6d3aa2	Vendor (CNA)
debian:linux	5.10.46-1 · Debian:12	Package registry (OSV)
suse:kernel-64kb	5.3.18-150300.59.161.1 · SUSE:Linux Enterprise High Performance Computing 15 SP3-LTSS	Package registry (OSV)
suse:kernel-default	5.3.18-150300.59.161.1 · SUSE:Linux Enterprise Live Patching 15 SP3	Package registry (OSV)
suse:kernel-default-base	5.3.18-150300.59.161.1.150300.18.94.1 · SUSE:Linux Enterprise High Performance Computing 15 SP3-LTSS	Package registry (OSV)
suse:kernel-docs	5.3.18-150300.59.161.2 · SUSE:Linux Enterprise High Performance Computing 15 SP3-LTSS	Package registry (OSV)
suse:kernel-livepatch-SLE15-SP3_Update_44	1-150300.7.3.1 · SUSE:Linux Enterprise Live Patching 15 SP3	Package registry (OSV)
suse:kernel-obs-build	5.3.18-150300.59.161.1 · SUSE:Linux Enterprise High Performance Computing 15 SP3-LTSS	Package registry (OSV)
suse:kernel-preempt	5.3.18-150300.59.161.1 · SUSE:Linux Enterprise High Performance Computing 15 SP3-LTSS	Package registry (OSV)
suse:kernel-rt	5.3.18-150300.169.1 · SUSE:Linux Enterprise Micro 5.1	Package registry (OSV)
suse:kernel-source	5.3.18-150300.59.161.1 · SUSE:Linux Enterprise High Performance Computing 15 SP3-LTSS	Package registry (OSV)
suse:kernel-source-rt	5.3.18-150300.169.1 · SUSE:Linux Enterprise Micro 5.1	Package registry (OSV)
suse:kernel-syms	5.3.18-150300.59.161.1 · SUSE:Linux Enterprise High Performance Computing 15 SP3-LTSS	Package registry (OSV)
suse:kernel-zfcpdump	5.3.18-150300.59.161.1 · SUSE:Linux Enterprise Server 15 SP3-LTSS	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.

National notice (Türkiye Cybersecurity Directorate / USOM)

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

TR-24-0494 · May 16, 2024(Linux Kernel Güncellemesi)
TR-24-0205 · Mar 20, 2024(Linux Kernel Güncellemesi)

All national notices →

Not on record for this CVE: EPSS history · patch commit or PR link · researcher credit · variant or chain candidate · public bounty program.

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 (1)

Fix✗ → ✓Sep 28, 2026, 10:11 PM UTC

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

References

git.kernel.org/stable/c/0f1e6fe66977a864fe850522316f713d7b926fd9

Show all references (2 more)

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

All records