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TI-2021-22177 Aliases CVE-2021-47527

serial: core: fix transmit-buffer reset and memleak

Priority LOW 24CWE-401Published · Updated

Key facts

Attack vector
Local
Privileges required
Low
User interaction
None
Attack complexity
Low
Impact type
Denial of service
Confidentiality · integrity · availability
None · None · High
Fix status
Partial Red Hat: 11 fixed, 2 without a fix

Attack profile from CVSS 3.1 · NVD. Fix status from CNA and Red Hat. Impact type from CWE-401.

Summary

In the Linux kernel, the following vulnerability has been resolved: serial: core: fix transmit-buffer reset and memleak Commit 761ed4a94582 ("tty: serial_core: convert uart_close to use tty_port_close") converted serial core to use tty_port_close() but failed to notice that the transmit buffer still needs to be freed on final close. Not freeing the transmit buffer means that the buffer is no longer cleared on next open so that any ioctl() waiting for the buffer to drain might wait indefinitely (e.g. on termios changes) or that stale data can end up being transmitted in case tx is restarted. Furthermore, the buffer of any port that has been opened would leak on driver unbind. Note that the port lock is held when clearing the buffer pointer due to the ldisc race worked around by commit a5ba1d95e46e ("uart: fix race between uart_put_char() and uart_shutdown()"). Also note that the tty-port shutdown() callback is not called for console ports so it is not strictly necessary to free the buffer page after releasing the lock (cf. d72402145ace ("tty/serial: do not free trasnmit buffer page under port lock")).

Why it matters now

Exploitation None reported CISA SSVC · not in CISA KEV
EPSS 0.00251 16th percentileScored 2026-11-07
Fix Partial Linux (Linux): 4.9.292, 4.14.257, 4.19.220 +4Red Hat: 3 advisoriesRed Hat: 11 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
LinuxLinux4.9 and later4.9.292, 4.14.257, 4.19.220, 5.4.164, 5.10.84, 5.15.7, 5.16Patch availableCNA
  • Linux VendorLinux Affected 4.9 and later Fixed in 4.9.292, 4.14.257, 4.19.220, 5.4.164, 5.10.84, 5.15.7, 5.16 Patch available CNA

CPE configurations NVD · 4

CPEVersionsRoleVendor
cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*4.9 to before 4.9.292; 4.10 to before 4.14.257; 4.15 to before 4.19.220; 4.20 to before 5.4.164; 5.5 to before 5.10.84; 5.11 to before 5.15.7VulnerableLinux
cpe:2.3:o:linux:linux_kernel:5.16:rc1:*:*:*:*:*:*5.16 rc1VulnerableLinux
cpe:2.3:o:linux:linux_kernel:5.16:rc2:*:*:*:*:*:*5.16 rc2VulnerableLinux
cpe:2.3:o:linux:linux_kernel:5.16:rc3:*:*:*:*:*:*5.16 rc3VulnerableLinux
  • cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* Versions 4.9 to before 4.9.292; 4.10 to before 4.14.257; 4.15 to before 4.19.220; 4.20 to before 5.4.164; 5.5 to before 5.10.84; 5.11 to before 5.15.7 Vulnerable ·Linux
  • cpe:2.3:o:linux:linux_kernel:5.16:rc1:*:*:*:*:*:* Versions 5.16 rc1 Vulnerable ·Linux
  • cpe:2.3:o:linux:linux_kernel:5.16:rc2:*:*:*:*:*:* Versions 5.16 rc2 Vulnerable ·Linux
  • cpe:2.3:o:linux:linux_kernel:5.16:rc3:*:*:*:*:*:* Versions 5.16 rc3 Vulnerable ·Linux

Remediation

  • Fix · CNA Linux (Linux) Fixed in 4.9.292, 4.14.257, 4.19.220, 5.4.164, 5.10.84, 5.15.7, 5.16

Red Hat 3 advisories

  • RHSA-2025:13135 Released 2025-08-06 · Red Hat rating Important
    kernel security update
    • Red Hat CodeReady Linux Builder EUS (v.9.4) kernel-tools-libs-devel-5.14.0-427.81.1.el9_4, libperf-5.14.0-427.81.1.el9_4
    • Red Hat Enterprise Linux AppStream EUS (v.9.4) kernel-64k-debug-devel-5.14.0-427.81.1.el9_4, kernel-64k-debug-devel-matched-5.14.0-427.81.1.el9_4, kernel-64k-devel-5.14.0-427.81.1.el9_4 +11
    • Red Hat Enterprise Linux BaseOS EUS (v.9.4) bpftool-7.3.0-427.81.1.el9_4, kernel-5.14.0-427.81.1.el9_4, kernel-64k-5.14.0-427.81.1.el9_4 +29
    • Red Hat Enterprise Linux Real Time EUS (v.9.4) kernel-rt-5.14.0-427.81.1.el9_4, kernel-rt-core-5.14.0-427.81.1.el9_4, kernel-rt-debug-5.14.0-427.81.1.el9_4 +9
    • Red Hat Enterprise Linux Real Time for NFV EUS (v.9.4) kernel-rt-5.14.0-427.81.1.el9_4, kernel-rt-core-5.14.0-427.81.1.el9_4, kernel-rt-debug-5.14.0-427.81.1.el9_4 +11
  • 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: Low. Red Hat's page for this CVE →

ProductStatusPlan or fix
Red Hat Enterprise Linux 7AffectedNo fix planned: Out of support scope
Red Hat Enterprise Linux 9AffectedNo fix yet
RHOAI-2.13-RHEL-8Fixed—
RHOAI-2.14-RHEL-8Fixed—
Red Hat CodeReady Linux Builder EUS (v.9.4)Fixed RHSA-2025:13135
Red Hat Enterprise Linux AppStream EUS (v.9.4)Fixed RHSA-2025:13135
Red Hat Enterprise Linux BaseOS (v. 8)Fixed RHSA-2024:7000
Red Hat Enterprise Linux BaseOS EUS (v.9.4)Fixed RHSA-2025:13135
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
Red Hat Enterprise Linux Real Time EUS (v.9.4)Fixed RHSA-2025:13135
Red Hat Enterprise Linux Real Time for NFV EUS (v.9.4)Fixed RHSA-2025:13135
Not affected: 1 product
  • Red Hat Enterprise Linux 6

Timeline

  1. 2026-10-02 Threatist record created from CVE-2021-47527
  2. 2026-10-31 Fix available: RHOAI-2.13-RHEL-8, RHOAI-2.14-RHEL-8 · Red Hat

References

Patch 7

  • 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