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NVD / CVE Program· CNA Linux

CVE-2021-47338: fbmem: Do not delete the mode that is still in use

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: 0.26% (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 087bff9acd2ec6db3f61aceb3224bde90fe0f7f8, 0af778269a522c988ef0b4188556aba97fb420cc, 359311b85ebec7c07c3a08ae2f3def946cad33fa.
  • Mentioned 1 time in Turkish national cyber security advisories (siberguvenlik.gov.tr).

Low priority for now. Upgrade to Linux Linux 087bff9acd2ec6db3f61aceb3224bde90fe0f7f8, 0af778269a522c988ef0b4188556aba97fb420cc, 359311b85ebec7c07c3a08ae2f3def946cad33fa 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: fbmem: Do not delete the mode that is still in use The execution of fb_delete_videomode() is not based on the result of the previous fbcon_mode_deleted(). As a result, the mode is directly deleted, regardless of whether it is still in use, which may cause UAF. ================================================================== BUG: KASAN: use-after-free in fb_mode_is_equal+0x36e/0x5e0 \ drivers/video/fbdev/core/modedb.c:924 Read of size 4 at addr ffff88807e0ddb1c by task syz-executor.0/18962 CPU: 2 PID: 18962 Comm: syz-executor.0 Not tainted 5.10.45-rc1+ #3 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS ... Call Trace: __dump_stack lib/dump_stack.c:77 [inline] dump_stack+0x137/0x1be lib/dump_stack.c:118 print_address_description+0x6c/0x640 mm/kasan/report.c:385 __kasan_report mm/kasan/report.c:545 [inline] kasan_report+0x13d/0x1e0 mm/kasan/report.c:562 fb_mode_is_equal+0x36e/0x5e0 drivers/video/fbdev/core/modedb.c:924 fbcon_mode_deleted+0x16a/0x220 drivers/video/fbdev/core/fbcon.c:2746 fb_set_var+0x1e1/0xdb0 drivers/video/fbdev/core/fbmem.c:975 do_fb_ioctl+0x4d9/0x6e0 drivers/video/fbdev/core/fbmem.c:1108 vfs_ioctl fs/ioctl.c:48 [inline] __do_sys_ioctl fs/ioctl.c:753 [inline] __se_sys_ioctl+0xfb/0x170 fs/ioctl.c:739 do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46 entry_SYSCALL_64_after_hwframe+0x44/0xa9 Freed by task 18960: kasan_save_stack mm/kasan/common.c:48 [inline] kasan_set_track+0x3d/0x70 mm/kasan/common.c:56 kasan_set_free_info+0x17/0x30 mm/kasan/generic.c:355 __kasan_slab_free+0x108/0x140 mm/kasan/common.c:422 slab_free_hook mm/slub.c:1541 [inline] slab_free_freelist_hook+0xd6/0x1a0 mm/slub.c:1574 slab_free mm/slub.c:3139 [inline] kfree+0xca/0x3d0 mm/slub.c:4121 fb_delete_videomode+0x56a/0x820 drivers/video/fbdev/core/modedb.c:1104 fb_set_var+0x1f3/0xdb0 drivers/video/fbdev/core/fbmem.c:978 do_fb_ioctl+0x4d9/0x6e0 drivers/video/fbdev/core/fbmem.c:1108 vfs_ioctl fs/ioctl.c:48 [inline] __do_sys_ioctl fs/ioctl.c:753 [inline] __se_sys_ioctl+0xfb/0x170 fs/ioctl.c:739 do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46 entry_SYSCALL_64_after_hwframe+0x44/0xa9

HighCVSS 7.8 · v3.1—No exploit Fix available
Published
May 21, 2024
Updated
Aug 5, 2026
EPSS
0.2% · 19th 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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When you'll hear from us

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  • when exploit code appears or is weaponized
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  • when EPSS rises 20 points in a week

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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 kernel5.3 and later · before 5.4.134
  • linux linux kernel5.5 and later · before 5.10.52
  • linux linux kernel5.11 and later · before 5.12.19
  • linux linux kernel5.13 and later · before 5.13.4
  • linux linux kernel5.14

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

    • 5.3affected
    • 13ff178ccd6d3b8074c542a911300b79c4eec255 and later · before 359311b85ebec7c07c3a08ae2f3def946cad33faaffected · git
    • 13ff178ccd6d3b8074c542a911300b79c4eec255 and later · before 087bff9acd2ec6db3f61aceb3224bde90fe0f7f8affected · git
    • 13ff178ccd6d3b8074c542a911300b79c4eec255 and later · before f193509afc7ff37a46862610c93b896044d5b693affected · git
    • 13ff178ccd6d3b8074c542a911300b79c4eec255 and later · before d6e76469157d8f240e5dec6f8411aa8d306b1126affected · git
    • 13ff178ccd6d3b8074c542a911300b79c4eec255 and later · before 0af778269a522c988ef0b4188556aba97fb420ccaffected · git
    • before 5.3not affected · semver
    • 5.4.134 and later · up to and including 5.4.*not affected · semver
    • 5.10.52 and later · up to and including 5.10.*not affected · semver
    • 5.12.19 and later · up to and including 5.12.*not affected · semver

Package-level exposure

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

EcosystemPackageAffected rangeFix
AlmaLinux:8bpftoolbefore 4.18.0-553.22.1.el8_104.18.0-553.22.1.el8_10
AlmaLinux:8kernelbefore 4.18.0-553.22.1.el8_104.18.0-553.22.1.el8_10
AlmaLinux:8kernel-abi-stablelistsbefore 4.18.0-553.22.1.el8_104.18.0-553.22.1.el8_10
AlmaLinux:8kernel-corebefore 4.18.0-553.22.1.el8_104.18.0-553.22.1.el8_10
AlmaLinux:8kernel-cross-headersbefore 4.18.0-553.22.1.el8_104.18.0-553.22.1.el8_10
AlmaLinux:8kernel-debugbefore 4.18.0-553.22.1.el8_104.18.0-553.22.1.el8_10
AlmaLinux:8kernel-debug-corebefore 4.18.0-553.22.1.el8_104.18.0-553.22.1.el8_10
AlmaLinux:8kernel-debug-develbefore 4.18.0-553.22.1.el8_104.18.0-553.22.1.el8_10
AlmaLinux:8kernel-debug-modulesbefore 4.18.0-553.22.1.el8_104.18.0-553.22.1.el8_10
AlmaLinux:8kernel-debug-modules-extrabefore 4.18.0-553.22.1.el8_104.18.0-553.22.1.el8_10
AlmaLinux:8kernel-develbefore 4.18.0-553.22.1.el8_104.18.0-553.22.1.el8_10
AlmaLinux:8kernel-docbefore 4.18.0-553.22.1.el8_104.18.0-553.22.1.el8_10
AlmaLinux:8kernel-headersbefore 4.18.0-553.22.1.el8_104.18.0-553.22.1.el8_10
AlmaLinux:8kernel-modulesbefore 4.18.0-553.22.1.el8_104.18.0-553.22.1.el8_10
AlmaLinux:8kernel-modules-extrabefore 4.18.0-553.22.1.el8_104.18.0-553.22.1.el8_10
AlmaLinux:8kernel-rtbefore 4.18.0-553.22.1.rt7.363.el8_104.18.0-553.22.1.rt7.363.el8_10
AlmaLinux:8kernel-rt-corebefore 4.18.0-553.22.1.rt7.363.el8_104.18.0-553.22.1.rt7.363.el8_10
AlmaLinux:8kernel-rt-debugbefore 4.18.0-553.22.1.rt7.363.el8_104.18.0-553.22.1.rt7.363.el8_10
AlmaLinux:8kernel-rt-debug-corebefore 4.18.0-553.22.1.rt7.363.el8_104.18.0-553.22.1.rt7.363.el8_10
AlmaLinux:8kernel-rt-debug-develbefore 4.18.0-553.22.1.rt7.363.el8_104.18.0-553.22.1.rt7.363.el8_10
AlmaLinux:8kernel-rt-debug-kvmbefore 4.18.0-553.22.1.rt7.363.el8_104.18.0-553.22.1.rt7.363.el8_10
AlmaLinux:8kernel-rt-debug-modulesbefore 4.18.0-553.22.1.rt7.363.el8_104.18.0-553.22.1.rt7.363.el8_10
AlmaLinux:8kernel-rt-debug-modules-extrabefore 4.18.0-553.22.1.rt7.363.el8_104.18.0-553.22.1.rt7.363.el8_10
AlmaLinux:8kernel-rt-develbefore 4.18.0-553.22.1.rt7.363.el8_104.18.0-553.22.1.rt7.363.el8_10

+65

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-2021-47336May 21, 2024 · smackfs: restrict bytes count in smk_set_cipso()
    31Monitor
  • ← EarlierCVE-2021-47337May 21, 2024 · scsi: core: Fix bad pointer dereference when ehandler kthread is invalid
    22Monitor
  • Later →CVE-2021-47339May 21, 2024 · media: v4l2-core: explicitly clear ioctl input data
    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 Linux087bff9acd2ec6db3f61aceb3224bde90fe0f7f8Vendor (CNA)
Linux Linux0af778269a522c988ef0b4188556aba97fb420ccVendor (CNA)
Linux Linux359311b85ebec7c07c3a08ae2f3def946cad33faVendor (CNA)
Linux Linuxd6e76469157d8f240e5dec6f8411aa8d306b1126Vendor (CNA)
Linux Linuxf193509afc7ff37a46862610c93b896044d5b693Vendor (CNA)
almalinux:bpftool4.18.0-553.22.1.el8_10 · AlmaLinux:8Package registry (OSV)
almalinux:kernel4.18.0-553.22.1.el8_10 · AlmaLinux:8Package registry (OSV)
almalinux:kernel-abi-stablelists4.18.0-553.22.1.el8_10 · AlmaLinux:8Package registry (OSV)
almalinux:kernel-core4.18.0-553.22.1.el8_10 · AlmaLinux:8Package registry (OSV)
almalinux:kernel-cross-headers4.18.0-553.22.1.el8_10 · AlmaLinux:8Package registry (OSV)
almalinux:kernel-debug4.18.0-553.22.1.el8_10 · AlmaLinux:8Package registry (OSV)
almalinux:kernel-debug-core4.18.0-553.22.1.el8_10 · AlmaLinux:8Package registry (OSV)
almalinux:kernel-debug-devel4.18.0-553.22.1.el8_10 · AlmaLinux:8Package registry (OSV)
almalinux:kernel-debug-modules4.18.0-553.22.1.el8_10 · AlmaLinux:8Package registry (OSV)
almalinux:kernel-debug-modules-extra4.18.0-553.22.1.el8_10 · AlmaLinux:8Package registry (OSV)
almalinux:kernel-devel4.18.0-553.22.1.el8_10 · AlmaLinux:8Package registry (OSV)
almalinux:kernel-doc4.18.0-553.22.1.el8_10 · AlmaLinux:8Package registry (OSV)
debian:linux5.14.6-1 · Debian:12Package registry (OSV)
red hat:bpftool0:4.18.0-553.22.1.el8_10 · Red Hat:enterprise_linux:8::baseosPackage registry (OSV)
red hat:bpftool-debuginfo0:4.18.0-553.22.1.el8_10 · Red Hat:enterprise_linux:8::baseosPackage registry (OSV)
red hat:kernel0:4.18.0-553.22.1.el8_10 · Red Hat:enterprise_linux:8::baseosPackage registry (OSV)
red hat:kernel-abi-stablelists0:4.18.0-553.22.1.el8_10 · Red Hat:enterprise_linux:8::baseosPackage registry (OSV)
red hat:kernel-core0:4.18.0-553.22.1.el8_10 · Red Hat:enterprise_linux:8::baseosPackage registry (OSV)
red hat:kernel-debug0:4.18.0-553.22.1.el8_10 · Red Hat:enterprise_linux:8::baseosPackage registry (OSV)
red hat:kernel-debug-core0:4.18.0-553.22.1.el8_10 · Red Hat:enterprise_linux:8::baseosPackage registry (OSV)
red hat:kernel-debug-debuginfo0:4.18.0-553.22.1.el8_10 · Red Hat:enterprise_linux:8::baseosPackage registry (OSV)
red hat:kernel-debug-devel0:4.18.0-553.22.1.el8_10 · Red Hat:enterprise_linux:8::baseosPackage registry (OSV)
red hat:kernel-debug-modules0:4.18.0-553.22.1.el8_10 · Red Hat:enterprise_linux:8::baseosPackage registry (OSV)
red hat:kernel-debug-modules-extra0:4.18.0-553.22.1.el8_10 · Red Hat:enterprise_linux:8::baseosPackage registry (OSV)
red hat:kernel-debuginfo0:4.18.0-553.22.1.el8_10 · Red Hat:enterprise_linux:8::baseosPackage 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.

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.
  • 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

c
free(dev->buf);/* ... another thread is still running ... */process(dev->buf);

Fixed

c
lock(&dev->lock);free(dev->buf);dev->buf = NULL;unlock(&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✗ → ✓

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