tty: xilinx_uartps: split sysrq handling
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
- Fixed
Attack profile from CVSS 3.1 · NVD. Fix status from CNA. Impact type from CWE-667 and the CVSS impact.
Summary
In the Linux kernel, the following vulnerability has been resolved: tty: xilinx_uartps: split sysrq handling lockdep detects the following circular locking dependency: CPU 0 CPU 1 ========================== ============================ cdns_uart_isr() printk() uart_port_lock(port) console_lock() cdns_uart_console_write() if (!port->sysrq) uart_port_lock(port) uart_handle_break() port->sysrq = ... uart_handle_sysrq_char() printk() console_lock() The fixed commit attempts to avoid this situation by only taking the port lock in cdns_uart_console_write if port->sysrq unset. However, if (as shown above) cdns_uart_console_write runs before port->sysrq is set, then it will try to take the port lock anyway. This may result in a deadlock. Fix this by splitting sysrq handling into two parts. We use the prepare helper under the port lock and defer handling until we release the lock.
Why it matters now
SSVC decision points
Not available: CISA has not published SSVC decision points for this record.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| Linux | Linux | 4.6 and later | 5.15.179, 6.1.129, 6.6.78, 6.12.14, 6.13.3, 6.14 | Patch available | CNA |
- Linux VendorLinux Affected 4.6 and later Fixed in 5.15.179, 6.1.129, 6.6.78, 6.12.14, 6.13.3, 6.14 Patch available CNA
CPE configurations NVD · 1
| CPE | Versions | Role | Vendor |
|---|---|---|---|
| cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* | 4.6 to before 6.1.129; 6.2 to before 6.6.78; 6.7 to before 6.12.14; 6.13 to before 6.13.3 | Vulnerable | Linux |
- cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:* Versions 4.6 to before 6.1.129; 6.2 to before 6.6.78; 6.7 to before 6.12.14; 6.13 to before 6.13.3 Vulnerable ·Linux
Remediation
- Fix · CNA Linux (Linux) Fixed in 5.15.179, 6.1.129, 6.6.78, 6.12.14, 6.13.3, 6.14
Vendor assessments
Red Hat
Red Hat rating: Moderate. Red Hat's page for this CVE →
Not affected: 5 products
- Red Hat Enterprise Linux 10
- Red Hat Enterprise Linux 6
- Red Hat Enterprise Linux 7
- Red Hat Enterprise Linux 8
- Red Hat Enterprise Linux 9
Timeline
- 2026-10-02 Threatist record created from CVE-2025-21820
- 2026-10-03 Alias added: GHSA-pgjm-rqqp-m93m
References
Patch 5
- https://git.kernel.org/stable/c/de5bd24197bd9ee37ec1e379a3d882bbd15c5065
- https://git.kernel.org/stable/c/8ea0e7b3d7b8f2f0fc9db491ff22a0abe120801c
- https://git.kernel.org/stable/c/9b88a7c4584ba67267a051069b8abe44fc9595b2
- https://git.kernel.org/stable/c/4410dba9807a17a93f649a9f5870ceaf30a675a3
- https://git.kernel.org/stable/c/b06f388994500297bb91be60ffaf6825ecfd2afe
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Sources
- CVE-2025-21820 · CVE Program
- CVE-2025-21820 · NVD
- FIRST EPSS
- GHSA-pgjm-rqqp-m93m · GitHub Advisory Database · CC BY 4.0
- CVE-2025-21820 · Red Hat security data · CC BY 4.0
This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences