Read the docs
TI-2021-21979 Aliases CVE-2021-47321GHSA-fhjr-hghh-2jv9

watchdog: Fix possible use-after-free by calling del_timer_sync()

Priority LOW 34CWE-416Published · Updated

Key facts

Attack vector
Local
Privileges required
Low
User interaction
None
Attack complexity
Low
Impact type
Code execution
Confidentiality · integrity · availability
High · High · High
Fix status
Partial Red Hat: 8 fixed, 2 without a fix

Attack profile from CVSS 3.1 · NVD. Fix status from CNA and Red Hat. Impact type from CWE-416 and the CVSS impact.

Summary

In the Linux kernel, the following vulnerability has been resolved: watchdog: Fix possible use-after-free by calling del_timer_sync() This driver's remove path calls del_timer(). However, that function does not wait until the timer handler finishes. This means that the timer handler may still be running after the driver's remove function has finished, which would result in a use-after-free. Fix by calling del_timer_sync(), which makes sure the timer handler has finished, and unable to re-schedule itself.

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00247 16th percentileScored 2026-11-07
Fix Partial Linux (Linux): 4.4.276, 4.9.276, 4.14.240 +6Red Hat: 3 advisoriesRed Hat: 8 fixed, 2 without a fix

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
None
Automatable
No
Technical impact
Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
LinuxLinux4.3 and later4.4.276, 4.9.276, 4.14.240, 4.19.198, 5.4.134, 5.10.52, 5.12.19, 5.13.4, 5.14Patch availableCNA
  • Linux VendorLinux Affected 4.3 and later Fixed in 4.4.276, 4.9.276, 4.14.240, 4.19.198, 5.4.134, 5.10.52, 5.12.19, 5.13.4, 5.14 Patch available CNA

CPE configurations NVD · 1

CPEVersionsRoleVendor
cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*before 4.4.276; 4.5 to before 4.9.276; 4.10 to before 4.14.240; 4.15 to before 4.19.198; 4.20 to before 5.4.134; 5.5 to before 5.10.52; 5.11 to before 5.12.9; 5.13 to before 5.13.4VulnerableLinux
  • cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* Versions before 4.4.276; 4.5 to before 4.9.276; 4.10 to before 4.14.240; 4.15 to before 4.19.198; 4.20 to before 5.4.134; 5.5 to before 5.10.52; 5.11 to before 5.12.9; 5.13 to before 5.13.4 Vulnerable ·Linux

Remediation

  • Fix · CNA Linux (Linux) Fixed in 4.4.276, 4.9.276, 4.14.240, 4.19.198, 5.4.134, 5.10.52, 5.12.19, 5.13.4, 5.14

Red Hat 3 advisories

  • RHSA-2024:8107 Released 2024-10-15 · Red Hat rating Moderate
    kernel security update
    • Red Hat CodeReady Linux Builder EUS (v.8.8) kernel-tools-libs-devel-4.18.0-477.75.1.el8_8
    • Red Hat Enterprise Linux BaseOS EUS (v.8.8) bpftool-4.18.0-477.75.1.el8_8, kernel-4.18.0-477.75.1.el8_8, kernel-abi-stablelists-4.18.0-477.75.1.el8_8 +19
  • RHSA-2024:7000 Released 2024-09-24 · Red Hat rating Important
    kernel security update
    • Red Hat Enterprise Linux BaseOS (v. 8) bpftool-4.18.0-553.22.1.el8_10, kernel-4.18.0-553.22.1.el8_10, kernel-abi-stablelists-4.18.0-553.22.1.el8_10 +19
    • Red Hat Enterprise Linux CRB (v. 8) kernel-tools-libs-devel-4.18.0-553.22.1.el8_10
  • RHSA-2024:7001 Released 2024-09-24 · Red Hat rating Important
    kernel-rt security update
    • Red Hat Enterprise Linux NFV (v. 8) kernel-rt-4.18.0-553.22.1.rt7.363.el8_10, kernel-rt-core-4.18.0-553.22.1.rt7.363.el8_10, kernel-rt-debug-4.18.0-553.22.1.rt7.363.el8_10 +9
    • Red Hat Enterprise Linux RT (v. 8) kernel-rt-4.18.0-553.22.1.rt7.363.el8_10, kernel-rt-core-4.18.0-553.22.1.rt7.363.el8_10, kernel-rt-debug-4.18.0-553.22.1.rt7.363.el8_10 +7

Vendor assessments

Red Hat

Red Hat rating: Moderate. Red Hat's page for this CVE →

ProductStatusPlan or fix
Red Hat Enterprise Linux 6AffectedNo fix planned: Out of support scope
Red Hat Enterprise Linux 7AffectedNo fix planned: Out of support scope
RHOAI-2.13-RHEL-8Fixed—
RHOAI-2.14-RHEL-8Fixed—
Red Hat CodeReady Linux Builder EUS (v.8.8)Fixed RHSA-2024:8107
Red Hat Enterprise Linux BaseOS (v. 8)Fixed RHSA-2024:7000
Red Hat Enterprise Linux BaseOS EUS (v.8.8)Fixed RHSA-2024:8107
Red Hat Enterprise Linux CRB (v. 8)Fixed RHSA-2024:7000
Red Hat Enterprise Linux NFV (v. 8)Fixed RHSA-2024:7001
Red Hat Enterprise Linux RT (v. 8)Fixed RHSA-2024:7001
Not affected: 1 product
  • Red Hat Enterprise Linux 9

Timeline

  1. 2026-10-02 Threatist record created from CVE-2021-47321
  2. 2026-10-03 Alias added: GHSA-fhjr-hghh-2jv9
  3. 2026-10-30 Fix available: RHOAI-2.13-RHEL-8, RHOAI-2.14-RHEL-8 · Red Hat

References

Patch 9

  • TI-2025-26358 tls: fix handling of zero-length records on the rx_list KEVCVSS 3.1CRITICAL 9.8
  • TI-2026-38352 netfilter: bridge: make ebt_snat ARP rewrite writable KEVCVSS 3.1HIGH 8.8
  • TI-2013-05264 The (1) get_user and (2) put_user API functions in the Linux kernel before 3.5.5 on the… KEVCVSS 3.1HIGH 8.8
  • TI-2022-00125 Integer overflow in kernel KEVCVSS 3.1HIGH 8.4
  • TI-2013-01864 The perf_swevent_init function in kernel/events/core.c in the Linux kernel before 3.8.9… KEVCVSS 3.1HIGH 8.4
  • TI-2021-05514 Heap Out-Of-Bounds Write in Netfilter IP6T_SO_SET_REPLACE KEVCVSS 3.1HIGH 8.3
See all 15278 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences