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NVD / CVE Program· CNA Linux

CVE-2021-47082: tun: avoid double free in tun_free_netdev

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: 0.25% (FIRST EPSS).
  • 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 0c0e566f0387490d16f166808c72e9c772027681, 158b515f703e75e7d68289bf4d98c664e1d632df, 3.11.
  • Mentioned 1 time in Turkish national cyber security advisories (siberguvenlik.gov.tr).

Low priority for now. Upgrade to Linux Linux 0c0e566f0387490d16f166808c72e9c772027681, 158b515f703e75e7d68289bf4d98c664e1d632df, 3.11 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: tun: avoid double free in tun_free_netdev Avoid double free in tun_free_netdev() by moving the dev->tstats and tun->security allocs to a new ndo_init routine (tun_net_init()) that will be called by register_netdevice(). ndo_init is paired with the desctructor (tun_free_netdev()), so if there's an error in register_netdevice() the destructor will handle the frees. BUG: KASAN: double-free or invalid-free in selinux_tun_dev_free_security+0x1a/0x20 security/selinux/hooks.c:5605 CPU: 0 PID: 25750 Comm: syz-executor416 Not tainted 5.16.0-rc2-syzk #1 Hardware name: Red Hat KVM, BIOS Call Trace: <TASK> __dump_stack lib/dump_stack.c:88 [inline] dump_stack_lvl+0x89/0xb5 lib/dump_stack.c:106 print_address_description.constprop.9+0x28/0x160 mm/kasan/report.c:247 kasan_report_invalid_free+0x55/0x80 mm/kasan/report.c:372 ____kasan_slab_free mm/kasan/common.c:346 [inline] __kasan_slab_free+0x107/0x120 mm/kasan/common.c:374 kasan_slab_free include/linux/kasan.h:235 [inline] slab_free_hook mm/slub.c:1723 [inline] slab_free_freelist_hook mm/slub.c:1749 [inline] slab_free mm/slub.c:3513 [inline] kfree+0xac/0x2d0 mm/slub.c:4561 selinux_tun_dev_free_security+0x1a/0x20 security/selinux/hooks.c:5605 security_tun_dev_free_security+0x4f/0x90 security/security.c:2342 tun_free_netdev+0xe6/0x150 drivers/net/tun.c:2215 netdev_run_todo+0x4df/0x840 net/core/dev.c:10627 rtnl_unlock+0x13/0x20 net/core/rtnetlink.c:112 __tun_chr_ioctl+0x80c/0x2870 drivers/net/tun.c:3302 tun_chr_ioctl+0x2f/0x40 drivers/net/tun.c:3311 vfs_ioctl fs/ioctl.c:51 [inline] __do_sys_ioctl fs/ioctl.c:874 [inline] __se_sys_ioctl fs/ioctl.c:860 [inline] __x64_sys_ioctl+0x19d/0x220 fs/ioctl.c:860 do_syscall_x64 arch/x86/entry/common.c:50 [inline] do_syscall_64+0x3a/0x80 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x44/0xae

HighCVSS 7.8 · v3.1—No exploit Fix available
Published
Mar 4, 2024
Updated
Aug 5, 2026
EPSS
0.2% · 16th percentile

Report tools

JSON

Action score

31

Monitor

Low priority for now.

CVSS
31 / 40 · 7.8 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.2%

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
7.8
agree

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.

VendorProduct
linuxlinux kernel

Affected versions

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

  • linux linux kernelbefore 4.19.280
  • linux linux kernel4.20 and later · before 5.4.240
  • linux linux kernel5.5 and later · before 5.10.136
  • linux linux kernel5.11 and later · before 5.15.12
  • linux linux kernel5.16

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

    • a81a02460bdf054ca0c60c5aed29941f7134092d, 6fc265f7a86d81e052508d03da555188f5882c3e, 3.12affected
    • 662ca437e714caaab855b12415d6ffd815985bc0 and later · before 8eb43d635950e27c29f1e9e49a23b31637f37757affected · git
    • 662ca437e714caaab855b12415d6ffd815985bc0 and later · before 0c0e566f0387490d16f166808c72e9c772027681affected · git
    • 662ca437e714caaab855b12415d6ffd815985bc0 and later · before a01a4e9f5dc93335c716fa4023b1901956e8c904affected · git
    • 662ca437e714caaab855b12415d6ffd815985bc0 and later · before 3cb5ae77799e8ed6ec3fec0b6b4cd07f01650cc5affected · git
    • 662ca437e714caaab855b12415d6ffd815985bc0 and later · before 158b515f703e75e7d68289bf4d98c664e1d632dfaffected · git
    • 3.10.16 and later · before 3.11affected · semver
    • 3.11.5 and later · before 3.12affected · semver
    • before 3.12not affected · semver
    • 4.19.280 and later · up to and including 4.19.*not affected · semver

Package-level exposure

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

EcosystemPackageAffected rangeFix
Debian:12linuxbefore 5.15.15-15.15.15-1
openSUSE:Leap 15.5dtb-aarch64before 5.14.21-150500.55.59.15.14.21-150500.55.59.1
openSUSE:Leap 15.5kernel-64kbbefore 5.14.21-150500.55.59.15.14.21-150500.55.59.1
openSUSE:Leap 15.5kernel-azurebefore 5.14.21-150500.33.48.15.14.21-150500.33.48.1
openSUSE:Leap 15.5kernel-debugbefore 5.14.21-150500.55.59.15.14.21-150500.55.59.1
openSUSE:Leap 15.5kernel-defaultbefore 5.14.21-150500.55.59.15.14.21-150500.55.59.1
openSUSE:Leap 15.5kernel-default-basebefore 5.14.21-150500.55.59.1.150500.6.25.75.14.21-150500.55.59.1.150500.6.25.7
openSUSE:Leap 15.5kernel-docsbefore 5.14.21-150500.55.59.15.14.21-150500.55.59.1
openSUSE:Leap 15.5kernel-kvmsmallbefore 5.14.21-150500.55.59.15.14.21-150500.55.59.1
openSUSE:Leap 15.5kernel-obs-buildbefore 5.14.21-150500.55.59.15.14.21-150500.55.59.1
openSUSE:Leap 15.5kernel-obs-qabefore 5.14.21-150500.55.59.15.14.21-150500.55.59.1
openSUSE:Leap 15.5kernel-rtbefore 5.14.21-150500.13.47.15.14.21-150500.13.47.1
openSUSE:Leap 15.5kernel-rt_debugbefore 5.14.21-150500.13.47.15.14.21-150500.13.47.1
openSUSE:Leap 15.5kernel-sourcebefore 5.14.21-150500.55.59.15.14.21-150500.55.59.1
openSUSE:Leap 15.5kernel-source-azurebefore 5.14.21-150500.33.48.15.14.21-150500.33.48.1
openSUSE:Leap 15.5kernel-source-rtbefore 5.14.21-150500.13.47.15.14.21-150500.13.47.1
openSUSE:Leap 15.5kernel-symsbefore 5.14.21-150500.55.59.15.14.21-150500.55.59.1
openSUSE:Leap 15.5kernel-syms-azurebefore 5.14.21-150500.33.48.15.14.21-150500.33.48.1
openSUSE:Leap 15.5kernel-syms-rtbefore 5.14.21-150500.13.47.15.14.21-150500.13.47.1
openSUSE:Leap 15.5kernel-zfcpdumpbefore 5.14.21-150500.55.59.15.14.21-150500.55.59.1
openSUSE:Leap Micro 5.3kernel-defaultbefore 5.14.21-150400.24.116.15.14.21-150400.24.116.1
openSUSE:Leap Micro 5.3kernel-default-basebefore 5.14.21-150400.24.116.1.150400.24.54.55.14.21-150400.24.116.1.150400.24.54.5
openSUSE:Leap Micro 5.3kernel-rtbefore 5.14.21-150400.15.76.15.14.21-150400.15.76.1
SUSE:Linux Enterprise High Performance Computing 15 SP4-ESPOSkernel-64kbbefore 5.14.21-150400.24.116.15.14.21-150400.24.116.1

+27

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-2023-52561Mar 2, 2024 · arm64: dts: qcom: sdm845-db845c: Mark cont splash memory region as reserved
    22Monitor
  • ← EarlierCVE-2024-26622Mar 4, 2024 · tomoyo: fix UAF write bug in tomoyo_write_control()
    31Monitor
  • Later →CVE-2021-47083Mar 4, 2024 · pinctrl: mediatek: fix global-out-of-bounds issue
    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 / packageFixed versionSource
Linux Linux0c0e566f0387490d16f166808c72e9c772027681Vendor (CNA)
Linux Linux158b515f703e75e7d68289bf4d98c664e1d632dfVendor (CNA)
Linux Linux3.11Vendor (CNA)
Linux Linux3.12Vendor (CNA)
Linux Linux3cb5ae77799e8ed6ec3fec0b6b4cd07f01650cc5Vendor (CNA)
Linux Linux8eb43d635950e27c29f1e9e49a23b31637f37757Vendor (CNA)
Linux Linuxa01a4e9f5dc93335c716fa4023b1901956e8c904Vendor (CNA)
debian:linux5.15.15-1 · Debian:12Package registry (OSV)
opensuse:dtb-aarch645.14.21-150500.55.59.1 · openSUSE:Leap 15.5Package registry (OSV)
opensuse:kernel-64kb5.14.21-150500.55.59.1 · openSUSE:Leap 15.5Package registry (OSV)
opensuse:kernel-debug5.14.21-150500.55.59.1 · openSUSE:Leap 15.5Package registry (OSV)
opensuse:kernel-default5.14.21-150400.24.116.1 · openSUSE:Leap Micro 5.3Package registry (OSV)
opensuse:kernel-default-base5.14.21-150400.24.116.1.150400.24.54.5 · openSUSE:Leap Micro 5.3Package registry (OSV)
opensuse:kernel-docs5.14.21-150500.55.59.1 · openSUSE:Leap 15.5Package registry (OSV)
opensuse:kernel-kvmsmall5.14.21-150500.55.59.1 · openSUSE:Leap 15.5Package registry (OSV)
opensuse:kernel-obs-build5.14.21-150500.55.59.1 · openSUSE:Leap 15.5Package registry (OSV)
opensuse:kernel-rt5.14.21-150400.15.76.1 · openSUSE:Leap Micro 5.3Package registry (OSV)
opensuse:kernel-rt_debug5.14.21-150500.13.47.1 · openSUSE:Leap 15.5Package registry (OSV)
opensuse:kernel-source-rt5.14.21-150500.13.47.1 · openSUSE:Leap 15.5Package registry (OSV)
opensuse:kernel-syms-rt5.14.21-150500.13.47.1 · openSUSE:Leap 15.5Package registry (OSV)
suse:kernel-64kb5.14.21-150400.24.116.1 · SUSE:Linux Enterprise High Performance Computing 15 SP4-ESPOSPackage registry (OSV)
suse:kernel-default5.14.21-150400.24.116.1 · SUSE:Linux Enterprise Micro 5.3Package registry (OSV)
suse:kernel-default-base5.14.21-150400.24.116.1.150400.24.54.5 · SUSE:Linux Enterprise Micro 5.3Package registry (OSV)
suse:kernel-docs5.14.21-150400.24.116.1 · SUSE:Linux Enterprise High Performance Computing 15 SP4-ESPOSPackage registry (OSV)
suse:kernel-livepatch-SLE15-SP4_Update_251-150400.9.5.1 · SUSE:Linux Enterprise Live Patching 15 SP4Package registry (OSV)
suse:kernel-livepatch-SLE15-SP5-RT_Update_131-150500.11.3.1 · SUSE:Linux Enterprise Live Patching 15 SP5Package registry (OSV)
suse:kernel-obs-build5.14.21-150400.24.116.1 · SUSE:Linux Enterprise High Performance Computing 15 SP4-ESPOSPackage registry (OSV)
suse:kernel-rt5.14.21-150400.15.76.1 · SUSE:Linux Enterprise Micro 5.3Package registry (OSV)
suse:kernel-source5.14.21-150400.24.116.1 · SUSE:Linux Enterprise High Performance Computing 15 SP4-ESPOSPackage registry (OSV)
suse:kernel-source-rt5.14.21-150400.15.76.1 · SUSE:Linux Enterprise Micro 5.3Package registry (OSV)

+2

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.

  • CVE-2024-3581474 days apartswiotlb: Fix double-allocation of slots due to broken alignment handling
    35Monitor
  • CVE-2020-367855 days apartmedia: atomisp: Fix use after free in atomisp_alloc_css_stat_bufs()
    31Monitor
  • CVE-2021-469386 days apartdm rq: fix double free of blk_mq_tag_set in dev remove after table load fails
    31Monitor
  • CVE-2021-4712311 days apartio_uring: fix ltout double free on completion race
    31Monitor
  • CVE-2023-5243913 days apartuio: Fix use-after-free in uio_open
    31Monitor
  • CVE-2024-2665328 days apartusb: misc: ljca: Fix double free in error handling path
    31Monitor

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.

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-415 · Double Free

CVSS vector

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

nvd-primary

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✗ → ✓

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

References

Show all references (4 more)

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

All records