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CVE-2021-47435· NVD / CVE Program· CNA Linux

dm: fix mempool NULL pointer race when completing IO

Noroxi assessment

Priority: Monitor (action score 18/100)

  • 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: 0.23% (FIRST EPSS).
  • Someone with local access to the system can trigger it. A low-privileged account is enough. No user action is required. Special conditions such as timing or configuration are required.
  • Fixed version: Linux Linux 6e506f07c5b561d673dd0b0d8f7f420cc48024fb, 9e07272cca2ed76f7f6073f4444b1143828c8d87, 9fb7cd5c7fef0f1c982e3cd27745a0dec260eaed.
  • Mentioned 1 time in Turkish national cyber security advisories (siberguvenlik.gov.tr).

Low priority for now. Upgrade to Linux Linux 6e506f07c5b561d673dd0b0d8f7f420cc48024fb, 9e07272cca2ed76f7f6073f4444b1143828c8d87, 9fb7cd5c7fef0f1c982e3cd27745a0dec260eaed 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: dm: fix mempool NULL pointer race when completing IO dm_io_dec_pending() calls end_io_acct() first and will then dec md in-flight pending count. But if a task is swapping DM table at same time this can result in a crash due to mempool->elements being NULL: task1 task2 do_resume ->do_suspend ->dm_wait_for_completion bio_endio ->clone_endio ->dm_io_dec_pending ->end_io_acct ->wakeup task1 ->dm_swap_table ->__bind ->__bind_mempools ->bioset_exit ->mempool_exit ->free_io [ 67.330330] Unable to handle kernel NULL pointer dereference at virtual address 0000000000000000 ...... [ 67.330494] pstate: 80400085 (Nzcv daIf +PAN -UAO) [ 67.330510] pc : mempool_free+0x70/0xa0 [ 67.330515] lr : mempool_free+0x4c/0xa0 [ 67.330520] sp : ffffff8008013b20 [ 67.330524] x29: ffffff8008013b20 x28: 0000000000000004 [ 67.330530] x27: ffffffa8c2ff40a0 x26: 00000000ffff1cc8 [ 67.330535] x25: 0000000000000000 x24: ffffffdada34c800 [ 67.330541] x23: 0000000000000000 x22: ffffffdada34c800 [ 67.330547] x21: 00000000ffff1cc8 x20: ffffffd9a1304d80 [ 67.330552] x19: ffffffdada34c970 x18: 000000b312625d9c [ 67.330558] x17: 00000000002dcfbf x16: 00000000000006dd [ 67.330563] x15: 000000000093b41e x14: 0000000000000010 [ 67.330569] x13: 0000000000007f7a x12: 0000000034155555 [ 67.330574] x11: 0000000000000001 x10: 0000000000000001 [ 67.330579] x9 : 0000000000000000 x8 : 0000000000000000 [ 67.330585] x7 : 0000000000000000 x6 : ffffff80148b5c1a [ 67.330590] x5 : ffffff8008013ae0 x4 : 0000000000000001 [ 67.330596] x3 : ffffff80080139c8 x2 : ffffff801083bab8 [ 67.330601] x1 : 0000000000000000 x0 : ffffffdada34c970 [ 67.330609] Call trace: [ 67.330616] mempool_free+0x70/0xa0 [ 67.330627] bio_put+0xf8/0x110 [ 67.330638] dec_pending+0x13c/0x230 [ 67.330644] clone_endio+0x90/0x180 [ 67.330649] bio_endio+0x198/0x1b8 [ 67.330655] dec_pending+0x190/0x230 [ 67.330660] clone_endio+0x90/0x180 [ 67.330665] bio_endio+0x198/0x1b8 [ 67.330673] blk_update_request+0x214/0x428 [ 67.330683] scsi_end_request+0x2c/0x300 [ 67.330688] scsi_io_completion+0xa0/0x710 [ 67.330695] scsi_finish_command+0xd8/0x110 [ 67.330700] scsi_softirq_done+0x114/0x148 [ 67.330708] blk_done_softirq+0x74/0xd0 [ 67.330716] __do_softirq+0x18c/0x374 [ 67.330724] irq_exit+0xb4/0xb8 [ 67.330732] __handle_domain_irq+0x84/0xc0 [ 67.330737] gic_handle_irq+0x148/0x1b0 [ 67.330744] el1_irq+0xe8/0x190 [ 67.330753] lpm_cpuidle_enter+0x4f8/0x538 [ 67.330759] cpuidle_enter_state+0x1fc/0x398 [ 67.330764] cpuidle_enter+0x18/0x20 [ 67.330772] do_idle+0x1b4/0x290 [ 67.330778] cpu_startup_entry+0x20/0x28 [ 67.330786] secondary_start_kernel+0x160/0x170 Fix this by: 1) Establishing pointers to 'struct dm_io' members in dm_io_dec_pending() so that they may be passed into end_io_acct() _after_ free_io() is called. 2) Moving end_io_acct() after free_io().

MediumCVSS 4.7 · v3.1—No exploit Fix available
Published
May 22, 2024
Updated
Jun 17, 2026
EPSS
0.2% · 13th percentile

Report tools

JSON

Action score

18

Monitor

Low priority for now.

CVSS
18 / 40 · 4.7 / 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.

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.

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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 4.9.313
  • linux linux kernel4.10 and later · before 4.14.278
  • linux linux kernel4.15 and later · before 4.19.242
  • linux linux kernel4.20 and later · before 5.4.193
  • linux linux kernel5.5 and later · before 5.10.113
  • linux linux kernel5.11 and later · before 5.14.14
  • linux linux kernel5.15

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

    • 2.6.37affected
    • 6a8736d10cb413be95ea443ba40f25c93f4ef9b2 and later · before 9fb7cd5c7fef0f1c982e3cd27745a0dec260eaedaffected · git
    • 6a8736d10cb413be95ea443ba40f25c93f4ef9b2 and later · before d35aef9c60d310eff3eaddacce301efe877e2b7caffected · git
    • 6a8736d10cb413be95ea443ba40f25c93f4ef9b2 and later · before 9e07272cca2ed76f7f6073f4444b1143828c8d87affected · git
    • 6a8736d10cb413be95ea443ba40f25c93f4ef9b2 and later · before ad1393b92e5059218d055bfec8f4946d85ad04c4affected · git
    • 6a8736d10cb413be95ea443ba40f25c93f4ef9b2 and later · before d29c78d3f9c5d2604548c1065bf1ec212728ea61affected · git
    • 6a8736d10cb413be95ea443ba40f25c93f4ef9b2 and later · before 6e506f07c5b561d673dd0b0d8f7f420cc48024fbaffected · git
    • 6a8736d10cb413be95ea443ba40f25c93f4ef9b2 and later · before d208b89401e073de986dc891037c5a668f5d5d95affected · git
    • before 2.6.37not affected · semver
    • 4.9.313 and later · up to and including 4.9.*not affected · semver

Package-level exposure

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

EcosystemPackageAffected rangeFix
Debian:12linuxbefore 5.14.16-15.14.16-1
Red Hat:rhel_eus:8.2::baseosbpftoolbefore 0:4.18.0-193.87.1.el8_20:4.18.0-193.87.1.el8_2
Red Hat:rhel_eus:8.2::baseosbpftool-debuginfobefore 0:4.18.0-193.87.1.el8_20:4.18.0-193.87.1.el8_2
Red Hat:rhel_eus:8.2::baseoskernelbefore 0:4.18.0-193.87.1.el8_20:4.18.0-193.87.1.el8_2
Red Hat:rhel_eus:8.2::baseoskernel-abi-whitelistsbefore 0:4.18.0-193.87.1.el8_20:4.18.0-193.87.1.el8_2
Red Hat:rhel_eus:8.2::baseoskernel-corebefore 0:4.18.0-193.87.1.el8_20:4.18.0-193.87.1.el8_2
Red Hat:rhel_eus:8.2::baseoskernel-debugbefore 0:4.18.0-193.87.1.el8_20:4.18.0-193.87.1.el8_2
Red Hat:rhel_eus:8.2::baseoskernel-debug-corebefore 0:4.18.0-193.87.1.el8_20:4.18.0-193.87.1.el8_2
Red Hat:rhel_eus:8.2::baseoskernel-debug-debuginfobefore 0:4.18.0-193.87.1.el8_20:4.18.0-193.87.1.el8_2
Red Hat:rhel_eus:8.2::baseoskernel-debug-develbefore 0:4.18.0-193.87.1.el8_20:4.18.0-193.87.1.el8_2
Red Hat:rhel_eus:8.2::baseoskernel-debug-modulesbefore 0:4.18.0-193.87.1.el8_20:4.18.0-193.87.1.el8_2
Red Hat:rhel_eus:8.2::baseoskernel-debug-modules-extrabefore 0:4.18.0-193.87.1.el8_20:4.18.0-193.87.1.el8_2
Red Hat:rhel_eus:8.2::baseoskernel-debuginfobefore 0:4.18.0-193.87.1.el8_20:4.18.0-193.87.1.el8_2
Red Hat:rhel_eus:8.2::baseoskernel-debuginfo-common-aarch64before 0:4.18.0-193.87.1.el8_20:4.18.0-193.87.1.el8_2
Red Hat:rhel_eus:8.2::baseoskernel-debuginfo-common-ppc64lebefore 0:4.18.0-193.87.1.el8_20:4.18.0-193.87.1.el8_2
Red Hat:rhel_eus:8.2::baseoskernel-debuginfo-common-s390xbefore 0:4.18.0-193.87.1.el8_20:4.18.0-193.87.1.el8_2
Red Hat:rhel_eus:8.2::baseoskernel-debuginfo-common-x86_64before 0:4.18.0-193.87.1.el8_20:4.18.0-193.87.1.el8_2
Red Hat:rhel_eus:8.2::baseoskernel-develbefore 0:4.18.0-193.87.1.el8_20:4.18.0-193.87.1.el8_2
Red Hat:rhel_eus:8.2::baseoskernel-docbefore 0:4.18.0-193.87.1.el8_20:4.18.0-193.87.1.el8_2
Red Hat:rhel_eus:8.2::baseoskernel-modulesbefore 0:4.18.0-193.87.1.el8_20:4.18.0-193.87.1.el8_2
Red Hat:rhel_eus:8.2::baseoskernel-modules-extrabefore 0:4.18.0-193.87.1.el8_20:4.18.0-193.87.1.el8_2
Red Hat:rhel_eus:8.2::baseoskernel-toolsbefore 0:4.18.0-193.87.1.el8_20:4.18.0-193.87.1.el8_2
Red Hat:rhel_eus:8.2::baseoskernel-tools-debuginfobefore 0:4.18.0-193.87.1.el8_20:4.18.0-193.87.1.el8_2
Red Hat:rhel_eus:8.2::baseoskernel-tools-libsbefore 0:4.18.0-193.87.1.el8_20:4.18.0-193.87.1.el8_2

+45

Same product

linux: all records

Other highest-scoring records for the same primary product.

  • 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
  • CVE-2016-5195Race condition in mm/gup.c in the Linux kernel 2.x through 4.x before 4.8.3 allows local users to gain privileges by leveraging incorrect haKEV
    83Now

Published before and after this one in the same product

  • ← EarlierCVE-2021-47433May 22, 2024 · btrfs: fix abort logic in btrfs_replace_file_extents
    22Monitor
  • ← EarlierCVE-2021-47434May 22, 2024 · xhci: Fix command ring pointer corruption while aborting a command
    22Monitor
  • Later →CVE-2021-47436May 22, 2024 · usb: musb: dsps: Fix the probe error path
    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 / packageFixed versionSource
Linux Linux6e506f07c5b561d673dd0b0d8f7f420cc48024fbVendor (CNA)
Linux Linux9e07272cca2ed76f7f6073f4444b1143828c8d87Vendor (CNA)
Linux Linux9fb7cd5c7fef0f1c982e3cd27745a0dec260eaedVendor (CNA)
Linux Linuxad1393b92e5059218d055bfec8f4946d85ad04c4Vendor (CNA)
Linux Linuxd208b89401e073de986dc891037c5a668f5d5d95Vendor (CNA)
Linux Linuxd29c78d3f9c5d2604548c1065bf1ec212728ea61Vendor (CNA)
Linux Linuxd35aef9c60d310eff3eaddacce301efe877e2b7cVendor (CNA)
debian:linux5.14.16-1 · Debian:12Package registry (OSV)
red hat:bpftool0:4.18.0-193.87.1.el8_2 · Red Hat:rhel_eus:8.2::baseosPackage registry (OSV)
red hat:bpftool-debuginfo0:4.18.0-193.87.1.el8_2 · Red Hat:rhel_eus:8.2::baseosPackage registry (OSV)
red hat:kernel0:4.18.0-193.87.1.el8_2 · Red Hat:rhel_eus:8.2::baseosPackage registry (OSV)
red hat:kernel-abi-whitelists0:4.18.0-193.87.1.el8_2 · Red Hat:rhel_eus:8.2::baseosPackage registry (OSV)
red hat:kernel-core0:4.18.0-193.87.1.el8_2 · Red Hat:rhel_eus:8.2::baseosPackage registry (OSV)
red hat:kernel-debug0:4.18.0-193.87.1.el8_2 · Red Hat:rhel_eus:8.2::baseosPackage registry (OSV)
red hat:kernel-debug-core0:4.18.0-193.87.1.el8_2 · Red Hat:rhel_eus:8.2::baseosPackage registry (OSV)
red hat:kernel-debug-debuginfo0:4.18.0-193.87.1.el8_2 · Red Hat:rhel_eus:8.2::baseosPackage registry (OSV)
red hat:kernel-debug-devel0:4.18.0-193.87.1.el8_2 · Red Hat:rhel_eus:8.2::baseosPackage registry (OSV)
red hat:kernel-debug-modules0:4.18.0-193.87.1.el8_2 · Red Hat:rhel_eus:8.2::baseosPackage registry (OSV)
red hat:kernel-debug-modules-extra0:4.18.0-193.87.1.el8_2 · Red Hat:rhel_eus:8.2::baseosPackage registry (OSV)
red hat:kernel-debuginfo0:4.18.0-193.87.1.el8_2 · Red Hat:rhel_eus:8.2::baseosPackage 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.

EPSS, last 120 days

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

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.

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.
  • Special conditions such as timing or configuration are required.

If successful

Confidentiality
none
Integrity
none
Availability
high · the service can be disrupted
Attack vector
Local
Attack complexity
High
Privileges required
Low
User interaction
None
Scope
Unchanged
Confidentiality impact
None
Integrity impact
None
Availability impact
High

Weakness class (CWE)

CWE-476 · NULL Pointer Dereference

CVSS vector

CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/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 (6 more)

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

All records