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NVD / CVE Program· CNA Linux

CVE-2021-47126: ipv6: Fix KASAN: slab-out-of-bounds Read in fib6_nh_flush_exceptions

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: 0.24% (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 09870235827451409ff546b073d754a19fd17e2e, 0a462e25ef0f7ab305081a08d435bbd1f13c0a94, 7ba7fa78a92dc410b6f93ed73075ab669c3a0b59.
  • Mentioned 1 time in Turkish national cyber security advisories (siberguvenlik.gov.tr).

Low priority for now. Upgrade to Linux Linux 09870235827451409ff546b073d754a19fd17e2e, 0a462e25ef0f7ab305081a08d435bbd1f13c0a94, 7ba7fa78a92dc410b6f93ed73075ab669c3a0b59 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: ipv6: Fix KASAN: slab-out-of-bounds Read in fib6_nh_flush_exceptions Reported by syzbot: HEAD commit: 90c911ad Merge tag 'fixes' of git://git.kernel.org/pub/scm.. git tree: git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git master dashboard link: https://syzkaller.appspot.com/bug?extid=123aa35098fd3c000eb7 compiler: Debian clang version 11.0.1-2 ================================================================== BUG: KASAN: slab-out-of-bounds in fib6_nh_get_excptn_bucket net/ipv6/route.c:1604 [inline] BUG: KASAN: slab-out-of-bounds in fib6_nh_flush_exceptions+0xbd/0x360 net/ipv6/route.c:1732 Read of size 8 at addr ffff8880145c78f8 by task syz-executor.4/17760 CPU: 0 PID: 17760 Comm: syz-executor.4 Not tainted 5.12.0-rc8-syzkaller #0 Call Trace: <IRQ> __dump_stack lib/dump_stack.c:79 [inline] dump_stack+0x202/0x31e lib/dump_stack.c:120 print_address_description+0x5f/0x3b0 mm/kasan/report.c:232 __kasan_report mm/kasan/report.c:399 [inline] kasan_report+0x15c/0x200 mm/kasan/report.c:416 fib6_nh_get_excptn_bucket net/ipv6/route.c:1604 [inline] fib6_nh_flush_exceptions+0xbd/0x360 net/ipv6/route.c:1732 fib6_nh_release+0x9a/0x430 net/ipv6/route.c:3536 fib6_info_destroy_rcu+0xcb/0x1c0 net/ipv6/ip6_fib.c:174 rcu_do_batch kernel/rcu/tree.c:2559 [inline] rcu_core+0x8f6/0x1450 kernel/rcu/tree.c:2794 __do_softirq+0x372/0x7a6 kernel/softirq.c:345 invoke_softirq kernel/softirq.c:221 [inline] __irq_exit_rcu+0x22c/0x260 kernel/softirq.c:422 irq_exit_rcu+0x5/0x20 kernel/softirq.c:434 sysvec_apic_timer_interrupt+0x91/0xb0 arch/x86/kernel/apic/apic.c:1100 </IRQ> asm_sysvec_apic_timer_interrupt+0x12/0x20 arch/x86/include/asm/idtentry.h:632 RIP: 0010:lock_acquire+0x1f6/0x720 kernel/locking/lockdep.c:5515 Code: f6 84 24 a1 00 00 00 02 0f 85 8d 02 00 00 f7 c3 00 02 00 00 49 bd 00 00 00 00 00 fc ff df 74 01 fb 48 c7 44 24 40 0e 36 e0 45 <4b> c7 44 3d 00 00 00 00 00 4b c7 44 3d 09 00 00 00 00 43 c7 44 3d RSP: 0018:ffffc90009e06560 EFLAGS: 00000206 RAX: 1ffff920013c0cc0 RBX: 0000000000000246 RCX: dffffc0000000000 RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000000 RBP: ffffc90009e066e0 R08: dffffc0000000000 R09: fffffbfff1f992b1 R10: fffffbfff1f992b1 R11: 0000000000000000 R12: 0000000000000000 R13: dffffc0000000000 R14: 0000000000000000 R15: 1ffff920013c0cb4 rcu_lock_acquire+0x2a/0x30 include/linux/rcupdate.h:267 rcu_read_lock include/linux/rcupdate.h:656 [inline] ext4_get_group_info+0xea/0x340 fs/ext4/ext4.h:3231 ext4_mb_prefetch+0x123/0x5d0 fs/ext4/mballoc.c:2212 ext4_mb_regular_allocator+0x8a5/0x28f0 fs/ext4/mballoc.c:2379 ext4_mb_new_blocks+0xc6e/0x24f0 fs/ext4/mballoc.c:4982 ext4_ext_map_blocks+0x2be3/0x7210 fs/ext4/extents.c:4238 ext4_map_blocks+0xab3/0x1cb0 fs/ext4/inode.c:638 ext4_getblk+0x187/0x6c0 fs/ext4/inode.c:848 ext4_bread+0x2a/0x1c0 fs/ext4/inode.c:900 ext4_append+0x1a4/0x360 fs/ext4/namei.c:67 ext4_init_new_dir+0x337/0xa10 fs/ext4/namei.c:2768 ext4_mkdir+0x4b8/0xc00 fs/ext4/namei.c:2814 vfs_mkdir+0x45b/0x640 fs/namei.c:3819 ovl_do_mkdir fs/overlayfs/overlayfs.h:161 [inline] ovl_mkdir_real+0x53/0x1a0 fs/overlayfs/dir.c:146 ovl_create_real+0x280/0x490 fs/overlayfs/dir.c:193 ovl_workdir_create+0x425/0x600 fs/overlayfs/super.c:788 ovl_make_workdir+0xed/0x1140 fs/overlayfs/super.c:1355 ovl_get_workdir fs/overlayfs/super.c:1492 [inline] ovl_fill_super+0x39ee/0x5370 fs/overlayfs/super.c:2035 mount_nodev+0x52/0xe0 fs/super.c:1413 legacy_get_tree+0xea/0x180 fs/fs_context.c:592 vfs_get_tree+0x86/0x270 fs/super.c:1497 do_new_mount fs/namespace.c:2903 [inline] path_mount+0x196f/0x2be0 fs/namespace.c:3233 do_mount fs/namespace.c:3246 [inline] __do_sys_mount fs/namespace.c:3454 [inline] __se_sys_mount+0x2f9/0x3b0 fs/namespace.c:3431 do_syscall_64+0x2d/0x70 arch/x86/entry/common.c:46 entry_SYSCALL_64_after_hwframe+0x44/0xae RIP: 0033:0x4665f9 Code: ff ff c3 66 2e 0f 1f 84 ---truncated---

Published
Mar 15, 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
—
CNA · Linux
7.8
NVD has not scored this yet; the score shown is the CNA’s.

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

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  • 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 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

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
    • f88d8ea67fbdbac7a64bfa6ed9a2ba27bb822f74 and later · before 7ba7fa78a92dc410b6f93ed73075ab669c3a0b59affected · git
    • f88d8ea67fbdbac7a64bfa6ed9a2ba27bb822f74 and later · before 09870235827451409ff546b073d754a19fd17e2eaffected · git
    • f88d8ea67fbdbac7a64bfa6ed9a2ba27bb822f74 and later · before 0a462e25ef0f7ab305081a08d435bbd1f13c0a94affected · git
    • f88d8ea67fbdbac7a64bfa6ed9a2ba27bb822f74 and later · before 821bbf79fe46a8b1d18aa456e8ed0a3c208c3754affected · git
    • before 5.3not affected · semver
    • 5.4.125 and later · up to and including 5.4.*not 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 (4)

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 5.4.125
  • linux linux kernel5.5 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.

EcosystemPackageAffected rangeFix
Debian:12linuxbefore 5.10.46-15.10.46-1
SUSE:Linux Enterprise High Performance Computing 15 SP2-LTSSkernel-default-basebefore 5.3.18-150200.24.200.1.150200.9.103.15.3.18-150200.24.200.1.150200.9.103.1
SUSE:Linux Enterprise High Performance Computing 15 SP2-LTSSkernel-docsbefore 5.3.18-150200.24.200.15.3.18-150200.24.200.1
SUSE:Linux Enterprise High Performance Computing 15 SP2-LTSSkernel-obs-buildbefore 5.3.18-150200.24.200.15.3.18-150200.24.200.1
SUSE:Linux Enterprise High Performance Computing 15 SP2-LTSSkernel-preemptbefore 5.3.18-150200.24.200.15.3.18-150200.24.200.1
SUSE:Linux Enterprise High Performance Computing 15 SP2-LTSSkernel-sourcebefore 5.3.18-150200.24.200.15.3.18-150200.24.200.1
SUSE:Linux Enterprise High Performance Computing 15 SP2-LTSSkernel-symsbefore 5.3.18-150200.24.200.15.3.18-150200.24.200.1
SUSE:Linux Enterprise High Performance Computing 15 SP3-LTSSkernel-64kbbefore 5.3.18-150300.59.170.15.3.18-150300.59.170.1
SUSE:Linux Enterprise High Performance Computing 15 SP3-LTSSkernel-default-basebefore 5.3.18-150300.59.170.1.150300.18.100.15.3.18-150300.59.170.1.150300.18.100.1
SUSE:Linux Enterprise High Performance Computing 15 SP3-LTSSkernel-docsbefore 5.3.18-150300.59.170.25.3.18-150300.59.170.2
SUSE:Linux Enterprise High Performance Computing 15 SP3-LTSSkernel-obs-buildbefore 5.3.18-150300.59.170.15.3.18-150300.59.170.1
SUSE:Linux Enterprise High Performance Computing 15 SP3-LTSSkernel-preemptbefore 5.3.18-150300.59.170.15.3.18-150300.59.170.1
SUSE:Linux Enterprise High Performance Computing 15 SP3-LTSSkernel-sourcebefore 5.3.18-150300.59.170.15.3.18-150300.59.170.1
SUSE:Linux Enterprise High Performance Computing 15 SP3-LTSSkernel-symsbefore 5.3.18-150300.59.170.15.3.18-150300.59.170.1
SUSE:Linux Enterprise Live Patching 15 SP2kernel-defaultbefore 5.3.18-150200.24.200.15.3.18-150200.24.200.1
SUSE:Linux Enterprise Live Patching 15 SP2kernel-livepatch-SLE15-SP2_Update_51before 1-150200.5.3.11-150200.5.3.1
SUSE:Linux Enterprise Live Patching 15 SP3kernel-defaultbefore 5.3.18-150300.59.170.15.3.18-150300.59.170.1
SUSE:Linux Enterprise Live Patching 15 SP3kernel-livepatch-SLE15-SP3_Update_47before 1-150300.7.3.11-150300.7.3.1
SUSE:Linux Enterprise Micro 5.1kernel-rtbefore 5.3.18-150300.178.15.3.18-150300.178.1
SUSE:Linux Enterprise Micro 5.1kernel-source-rtbefore 5.3.18-150300.178.15.3.18-150300.178.1
SUSE:Linux Enterprise Server 15 SP3-LTSSkernel-zfcpdumpbefore 5.3.18-150300.59.170.15.3.18-150300.59.170.1

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-2021-47124Mar 15, 2024 · io_uring: fix link timeout refs
    22Monitor
  • ← EarlierCVE-2021-47125Mar 15, 2024 · sch_htb: fix refcount leak in htb_parent_to_leaf_offload
    22Monitor
  • Later →CVE-2021-47127Mar 15, 2024 · ice: track AF_XDP ZC enabled queues in bitmap
    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 Linux09870235827451409ff546b073d754a19fd17e2eVendor (CNA)
Linux Linux0a462e25ef0f7ab305081a08d435bbd1f13c0a94Vendor (CNA)
Linux Linux7ba7fa78a92dc410b6f93ed73075ab669c3a0b59Vendor (CNA)
Linux Linux821bbf79fe46a8b1d18aa456e8ed0a3c208c3754Vendor (CNA)
debian:linux5.10.46-1 · Debian:12Package registry (OSV)
suse:kernel-64kb5.3.18-150300.59.170.1 · SUSE:Linux Enterprise High Performance Computing 15 SP3-LTSSPackage registry (OSV)
suse:kernel-default5.3.18-150200.24.200.1 · SUSE:Linux Enterprise Live Patching 15 SP2Package registry (OSV)
suse:kernel-default-base5.3.18-150200.24.200.1.150200.9.103.1 · SUSE:Linux Enterprise High Performance Computing 15 SP2-LTSSPackage registry (OSV)
suse:kernel-docs5.3.18-150200.24.200.1 · SUSE:Linux Enterprise High Performance Computing 15 SP2-LTSSPackage registry (OSV)
suse:kernel-livepatch-SLE15-SP2_Update_511-150200.5.3.1 · SUSE:Linux Enterprise Live Patching 15 SP2Package registry (OSV)
suse:kernel-livepatch-SLE15-SP3_Update_471-150300.7.3.1 · SUSE:Linux Enterprise Live Patching 15 SP3Package registry (OSV)
suse:kernel-obs-build5.3.18-150200.24.200.1 · SUSE:Linux Enterprise High Performance Computing 15 SP2-LTSSPackage registry (OSV)
suse:kernel-preempt5.3.18-150200.24.200.1 · SUSE:Linux Enterprise High Performance Computing 15 SP2-LTSSPackage registry (OSV)
suse:kernel-rt5.3.18-150300.178.1 · SUSE:Linux Enterprise Micro 5.1Package registry (OSV)
suse:kernel-source5.3.18-150200.24.200.1 · SUSE:Linux Enterprise High Performance Computing 15 SP2-LTSSPackage registry (OSV)
suse:kernel-source-rt5.3.18-150300.178.1 · SUSE:Linux Enterprise Micro 5.1Package registry (OSV)
suse:kernel-syms5.3.18-150200.24.200.1 · SUSE:Linux Enterprise High Performance Computing 15 SP2-LTSSPackage 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.

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-125 · Out-of-bounds Read

CVSS vector

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

nvd-secondary

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

—

References

Show all references (3 more)

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

All records