Skip to content
Noroxi
NVD / CVE Program· CNA redhat

CVE-2021-3640: A flaw use-after-free in function sco_sock_sendmsg() of the Linux kernel HCI subsystem was found in the way user calls ioct UFFDIO_REGISTER

Noroxi assessment

Priority: Monitor (action score 28/100)

  • 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: 0.37% (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: bpftool (AlmaLinux:8) 4.18.0-425.3.1.el8; kernel (AlmaLinux:8) 4.18.0-425.3.1.el8; kernel-abi-stablelists (AlmaLinux:8) 4.18.0-425.3.1.el8.
  • Mentioned 1 time in Turkish national cyber security advisories (siberguvenlik.gov.tr).

Low priority for now. Upgrade to bpftool (AlmaLinux:8) 4.18.0-425.3.1.el8; kernel (AlmaLinux:8) 4.18.0-425.3.1.el8; kernel-abi-stablelists (AlmaLinux:8) 4.18.0-425.3.1.el8 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

A flaw use-after-free in function sco_sock_sendmsg() of the Linux kernel HCI subsystem was found in the way user calls ioct UFFDIO_REGISTER or other way triggers race condition of the call sco_conn_del() together with the call sco_sock_sendmsg() with the expected controllable faulting memory page. A privileged local user could use this flaw to crash the system or escalate their privileges on the system.

HighCVSS 7.0 · v3.1—No exploit Fix available
Published
Mar 3, 2022
Updated
Jun 17, 2026
EPSS
0.3% · 30th percentile

Report tools

JSON

Action score

28

Monitor

Low priority for now.

CVSS
28 / 40 · 7.0 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.3%

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.

Follow CVE-2021-3640

When you'll hear from us

  • when it enters CISA KEV
  • when exploit code appears or is weaponized
  • when the record is updated (including a fixed version)
  • when EPSS rises 20 points in a week

One daily email digest (06:00 UTC); connect a webhook for KEV listings and weaponized exploits instantly.

Your free account also gets you

Running WordPress? Scan your site free with WP Lens

  • Stack alerts: add the products and versions you run, get the new CVEs that affect them
  • Uptime monitoring: 1 site, instant email when it goes down
  • Add your domain: subdomains and takeover risk scanned every week (1 domain)
  • 10 scans an hour on the security tools (3 a day without an account), an API key and MCP
  • All your scans in one panel: findings, what changed in the last scan, a report per domain or per client (PDF, share link)
All free tools

Sign up with email · Have an account? Sign in

Free account, no card. Unfollow any time.

Don't want an account? Get "Exploited this week" by email every MondayDon't want an account? RSS feed for linux records

Running WordPress? Scan your site free with WP Lens

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.

We use this product, ask for help

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
debiandebian linux
fedoraprojectfedora
canonicalubuntu linux
netapph300s firmware
netapph300s
netapph700s firmware
netapph700s
netapph300e firmware
netapph300e
netapph500e firmware
netapph500e

and 8 more

Affected versions

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

  • canonical ubuntu linux14.04
  • canonical ubuntu linux16.04
  • canonical ubuntu linux18.04
  • canonical ubuntu linux20.04
  • canonical ubuntu linux21.10
  • debian debian linux9.0
  • fedoraproject fedora34
  • linux linux kernel5.15 and later · before 5.15.3
  • linux linux kernelbefore 4.4.293
  • linux linux kernel4.5 and later · before 4.9.291
  • linux linux kernel4.10 and later · before 4.14.256
  • linux linux kernel4.15 and later · before 4.19.218
  • linux linux kernel4.20 and later · before 5.4.160
  • linux linux kernel5.5.0 and later · before 5.10.80
  • linux linux kernel5.11 and later · before 5.14.19
  • netapp h300e firmwareall versions
  • netapp h300s firmwareall versions
  • netapp h410c firmwareall versions
  • netapp h410s firmwareall versions
  • netapp h500e firmwareall versions

Versions reported by the vendor

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

  • n/a kernel

    • Affects kernel v5.15.3 and prior, Fixed in v5.16-rc1 and above.affected

Package-level exposure

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

EcosystemPackageAffected rangeFix
AlmaLinux:8bpftoolbefore 4.18.0-425.3.1.el84.18.0-425.3.1.el8
AlmaLinux:8kernelbefore 4.18.0-425.3.1.el84.18.0-425.3.1.el8
AlmaLinux:8kernel-abi-stablelistsbefore 4.18.0-425.3.1.el84.18.0-425.3.1.el8
AlmaLinux:8kernel-corebefore 4.18.0-425.3.1.el84.18.0-425.3.1.el8
AlmaLinux:8kernel-cross-headersbefore 4.18.0-425.3.1.el84.18.0-425.3.1.el8
AlmaLinux:8kernel-debugbefore 4.18.0-425.3.1.el84.18.0-425.3.1.el8
AlmaLinux:8kernel-debug-corebefore 4.18.0-425.3.1.el84.18.0-425.3.1.el8
AlmaLinux:8kernel-debug-develbefore 4.18.0-425.3.1.el84.18.0-425.3.1.el8
AlmaLinux:8kernel-debug-modulesbefore 4.18.0-425.3.1.el84.18.0-425.3.1.el8
AlmaLinux:8kernel-debug-modules-extrabefore 4.18.0-425.3.1.el84.18.0-425.3.1.el8
AlmaLinux:8kernel-develbefore 4.18.0-425.3.1.el84.18.0-425.3.1.el8
AlmaLinux:8kernel-docbefore 4.18.0-425.3.1.el84.18.0-425.3.1.el8
AlmaLinux:8kernel-headersbefore 4.18.0-425.3.1.el84.18.0-425.3.1.el8
AlmaLinux:8kernel-modulesbefore 4.18.0-425.3.1.el84.18.0-425.3.1.el8
AlmaLinux:8kernel-modules-extrabefore 4.18.0-425.3.1.el84.18.0-425.3.1.el8
AlmaLinux:8kernel-rtbefore 4.18.0-425.3.1.rt7.213.el84.18.0-425.3.1.rt7.213.el8
AlmaLinux:8kernel-rt-corebefore 4.18.0-425.3.1.rt7.213.el84.18.0-425.3.1.rt7.213.el8
AlmaLinux:8kernel-rt-debugbefore 4.18.0-425.3.1.rt7.213.el84.18.0-425.3.1.rt7.213.el8
AlmaLinux:8kernel-rt-debug-corebefore 4.18.0-425.3.1.rt7.213.el84.18.0-425.3.1.rt7.213.el8
AlmaLinux:8kernel-rt-debug-develbefore 4.18.0-425.3.1.rt7.213.el84.18.0-425.3.1.rt7.213.el8
AlmaLinux:8kernel-rt-debug-kvmbefore 4.18.0-425.3.1.rt7.213.el84.18.0-425.3.1.rt7.213.el8
AlmaLinux:8kernel-rt-debug-modulesbefore 4.18.0-425.3.1.rt7.213.el84.18.0-425.3.1.rt7.213.el8
AlmaLinux:8kernel-rt-debug-modules-extrabefore 4.18.0-425.3.1.rt7.213.el84.18.0-425.3.1.rt7.213.el8
AlmaLinux:8kernel-rt-develbefore 4.18.0-425.3.1.rt7.213.el84.18.0-425.3.1.rt7.213.el8

+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-2022-0492Mar 3, 2022 · A vulnerability was found in the Linux kernel’s cgroup_release_agent_write in the kernel/cgroup/cgroup-v1.c function.KEV
    63This week
  • ← EarlierCVE-2021-4002Mar 3, 2022 · A memory leak flaw in the Linux kernel's hugetlbfs memory usage was found in the way the user maps some regions of memory twice using shmget
    17Monitor
  • Later →CVE-2021-3743Mar 4, 2022 · An out-of-bounds (OOB) memory read flaw was found in the Qualcomm IPC router protocol in the Linux kernel.
    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
almalinux:kernel-rt4.18.0-425.3.1.rt7.213.el8 · AlmaLinux:8Package registry (OSV)
almalinux:kernel-rt-core4.18.0-425.3.1.rt7.213.el8 · AlmaLinux:8Package registry (OSV)
almalinux:kernel-rt-debug4.18.0-425.3.1.rt7.213.el8 · AlmaLinux:8Package registry (OSV)
almalinux:kernel-rt-debug-core4.18.0-425.3.1.rt7.213.el8 · AlmaLinux:8Package registry (OSV)
almalinux:kernel-rt-debug-devel4.18.0-425.3.1.rt7.213.el8 · AlmaLinux:8Package registry (OSV)
almalinux:kernel-rt-debug-kvm4.18.0-425.3.1.rt7.213.el8 · AlmaLinux:8Package registry (OSV)
almalinux:kernel-rt-debug-modules4.18.0-425.3.1.rt7.213.el8 · AlmaLinux:8Package registry (OSV)
almalinux:kernel-rt-debug-modules-extra4.18.0-425.3.1.rt7.213.el8 · AlmaLinux:8Package registry (OSV)
almalinux:kernel-rt-devel4.18.0-425.3.1.rt7.213.el8 · AlmaLinux:8Package registry (OSV)
almalinux:kernel-rt-kvm4.18.0-425.3.1.rt7.213.el8 · AlmaLinux:8Package registry (OSV)
almalinux:kernel-rt-modules4.18.0-425.3.1.rt7.213.el8 · AlmaLinux:8Package registry (OSV)
almalinux:kernel-rt-modules-extra4.18.0-425.3.1.rt7.213.el8 · AlmaLinux:8Package registry (OSV)
debian:linux5.15.3-1 · Debian:12Package registry (OSV)
debian:linux-4.194.19.232-1~deb9u1 · Debian:9Package registry (OSV)
opensuse:kernel-azure5.3.18-38.22.2 · openSUSE:Leap 15.3Package registry (OSV)
opensuse:kernel-debug5.3.18-lp152.92.2 · openSUSE:Leap 15.2Package registry (OSV)
opensuse:kernel-default5.3.18-lp152.92.2 · openSUSE:Leap 15.2Package registry (OSV)
opensuse:kernel-default-base5.3.18-lp152.92.2.lp152.8.42.3 · openSUSE:Leap 15.2Package registry (OSV)
opensuse:kernel-docs5.3.18-lp152.92.1 · openSUSE:Leap 15.2Package registry (OSV)
opensuse:kernel-kvmsmall5.3.18-lp152.92.2 · openSUSE:Leap 15.2Package registry (OSV)
opensuse:kernel-obs-build5.3.18-lp152.92.2 · openSUSE:Leap 15.2Package registry (OSV)
opensuse:kernel-obs-qa5.3.18-lp152.92.1 · openSUSE:Leap 15.2Package registry (OSV)
opensuse:kernel-preempt5.3.18-lp152.92.2 · openSUSE:Leap 15.2Package registry (OSV)
opensuse:kernel-source5.3.18-lp152.92.2 · openSUSE:Leap 15.2Package registry (OSV)
opensuse:kernel-source-azure5.3.18-38.22.1 · openSUSE:Leap 15.3Package registry (OSV)
opensuse:kernel-syms5.3.18-lp152.92.1 · openSUSE:Leap 15.2Package registry (OSV)
red hat:kernel-rt0:4.18.0-425.3.1.rt7.213.el8 · Red Hat:enterprise_linux:8::nfvPackage registry (OSV)
red hat:kernel-rt-core0:4.18.0-425.3.1.rt7.213.el8 · Red Hat:enterprise_linux:8::nfvPackage registry (OSV)
red hat:kernel-rt-debug0:4.18.0-425.3.1.rt7.213.el8 · Red Hat:enterprise_linux:8::nfvPackage registry (OSV)
red hat:kernel-rt-debug-core0:4.18.0-425.3.1.rt7.213.el8 · Red Hat:enterprise_linux:8::nfvPackage registry (OSV)

+22

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.

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
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
High
Privileges required
Low
User interaction
None
Scope
Unchanged
Confidentiality impact
High
Integrity impact
High
Availability impact
High

Weakness class (CWE)

CWE-362 · Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition')

CVSS vector

CVSS:3.1/AV:L/AC:H/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.

ATT&CK techniques

—

Change log

  1. Fix✗ → ✓

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

References

Show all references (7 more)

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

All records