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CVE-2025-21820— tty: xilinx_uartps: split sysrq handling

Quick assessment

Affected
Linux Linux
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Linux kernel是美国Linux基金会的开源操作系统Linux所使用的内核。 Linux kernel存在安全漏洞，该漏洞源于cdns_uart_console_write函数中未正确处理sysrq，可能导致死锁。

AI Predicted 7.8 Difficulty: Hard EPSS 0.16% · P6

Affected Version Matrix 14

VendorProduct Version RangeStatus
Linux Linux 74ea66d4ca061a3cd4c0e924e51b60e924644852< e22a97700901ba5e8bf8db68056a0d50f9440cae affected
74ea66d4ca061a3cd4c0e924e51b60e924644852< de5bd24197bd9ee37ec1e379a3d882bbd15c5065 affected
74ea66d4ca061a3cd4c0e924e51b60e924644852< 8ea0e7b3d7b8f2f0fc9db491ff22a0abe120801c affected
74ea66d4ca061a3cd4c0e924e51b60e924644852< 9b88a7c4584ba67267a051069b8abe44fc9595b2 affected
74ea66d4ca061a3cd4c0e924e51b60e924644852< 4410dba9807a17a93f649a9f5870ceaf30a675a3 affected
74ea66d4ca061a3cd4c0e924e51b60e924644852< b06f388994500297bb91be60ffaf6825ecfd2afe affected
4.6 affected
< 4.6 unaffected
… +6 more rows
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I. Basic Information for CVE-2025-21820

Vulnerability Information
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Vulnerability Title
tty: xilinx_uartps: split sysrq handling
Source: CVE Program / CVE List V5
Vulnerability Description
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.
Source: CVE Program / CVE List V5
CVSS Information
N/A
Source: CVE Program / CVE List V5
Vulnerability Type
N/A
Source: CVE Program / CVE List V5
Vulnerability Title
Linux kernel 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Linux kernel是美国Linux基金会的开源操作系统Linux所使用的内核。 Linux kernel存在安全漏洞，该漏洞源于cdns_uart_console_write函数中未正确处理sysrq，可能导致死锁。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
Linux Linux 74ea66d4ca061a3cd4c0e924e51b60e924644852 ~ e22a97700901ba5e8bf8db68056a0d50f9440cae -
Linux Linux 4.6 -

II. Public POCs for CVE-2025-21820

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III. Intelligence Information for CVE-2025-21820

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Patches & Fixes for CVE-2025-21820 (5)

Other References for CVE-2025-21820 (1)

Same Patch Batch · Linux · 2025-02-27 · 177 CVEs total

CVE-2025-21805 9.8 CRITICAL RDMA/rtrs: Add missing deinit() call
CVE-2025-21796 9.8 CRITICAL nfsd: clear acl_access/acl_default after releasing them
CVE-2025-21707 9.8 CRITICAL mptcp: consolidate suboption status
CVE-2025-21748 9.8 CRITICAL ksmbd: fix integer overflows on 32 bit systems
CVE-2024-58006 9.6 CRITICAL PCI: dwc: ep: Prevent changing BAR size/flags in pci_epc_set_bar()
CVE-2024-57999 8.8 HIGH powerpc/pseries/iommu: IOMMU incorrectly marks MMIO range in DDW
CVE-2025-21735 8.8 HIGH NFC: nci: Add bounds checking in nci_hci_create_pipe()
CVE-2024-57997 8.8 HIGH wifi: wcn36xx: fix channel survey memory allocation size
CVE-2024-57995 8.8 HIGH wifi: ath12k: fix read pointer after free in ath12k_mac_assign_vif_to_vdev()
CVE-2025-21710 8.2 HIGH tcp: correct handling of extreme memory squeeze
CVE-2025-21766 8.1 HIGH ipv4: use RCU protection in __ip_rt_update_pmtu()
CVE-2024-57973 8.1 HIGH rdma/cxgb4: Prevent potential integer overflow on 32bit
CVE-2025-21765 8.1 HIGH ipv6: use RCU protection in ip6_default_advmss()
CVE-2025-21760 8.1 HIGH ndisc: extend RCU protection in ndisc_send_skb()
CVE-2025-21762 8.1 HIGH arp: use RCU protection in arp_xmit()
CVE-2024-58010 7.8 HIGH binfmt_flat: Fix integer overflow bug on 32 bit systems
CVE-2024-58008 7.8 HIGH KEYS: trusted: dcp: fix improper sg use with CONFIG_VMAP_STACK=y
CVE-2025-21764 7.8 HIGH ndisc: use RCU protection in ndisc_alloc_skb()
CVE-2025-21791 7.8 HIGH vrf: use RCU protection in l3mdev_l3_out()
CVE-2025-21763 7.8 HIGH neighbour: use RCU protection in __neigh_notify()

Showing top 20 of 177 CVEs. View all on vendor page &rarr; →

IV. Related Vulnerabilities

Same product: Linux
Same vendor: Linux

V. Comments for CVE-2025-21820

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