5.5

CVE-2025-21820: linux Improper Locking

CVSS: 5.5v3.1MediumModified
AliasesUBUNTU-CVE-2025-21820DEBIAN-CVE-2025-21820
Published 27-02-2025Last modified 11-05-2026
Open JSON

Vulnerability summary

CVE-2025-21820 is a medium (CVSS 5.5) Improper Locking vulnerability in linux. EPSS estimates a 0.17% chance of exploitation in the next 30 days, higher than 5.3% of scored vulnerabilities.

Overall risk
22/100
0100
Low · default modelHow is this calculated?
CVSS score
5.5/10
010
Medium · v3.1 (NVD)
EPSS score
0.17%
0%100%
Low · 0.00 pp in 30 days
KEVNot listedIn no KEV catalog
RansomwareNone recordedNo known use recorded
Public exploits0No public exploits recorded

Advisory lineage

Upstream 0 · Downstream 34 · Related 34
DLA-4102-1SUSE-SU-2025:01919-1SUSE-SU-2025:1177-1SUSE-SU-2025:1178-1SUSE-SU-2025:1180-1SUSE-SU-2025:20190-1

Timeline

  1. 27-02-2025
    PublishedVulnerability first disclosed.
  2. 11-05-2026
    Last modifiedVulnerability information updated.

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.

CVSS metrics

3 scores · 3 sources · 1 version

EPSS trend

Probability

0.17%

Chance of exploitation in the next 30 days

Percentile

5%

Versus all other CVEs

30-day change

0.00 pp

From 0.16% on 19-09-2026

19-09-202619-10-2026
EPSS score
0.17%

Known exploited

Compare KEV catalogs

Not in any of the 3 tracked catalogs.

Public exploits

0 found

No public exploits indexed.

Weaknesses

CWE · root cause

Affected systems

Ubuntu135 products
  • linuxAll versions (No fix recorded) | < 5.15.0-140.150 | < 6.8.0-64.67
  • linux-allwinner-5.19All versions (No fix recorded)
  • linux-awsAll versions (No fix recorded) | < 5.15.0-1084.91 | < 6.8.0-1032.34
  • linux-aws-5.0All versions (No fix recorded)
  • linux-aws-5.11All versions (No fix recorded)
Linux2 products
  • linux≥ 74ea66d4ca061a3cd4c0e924e51b60e924644852, < e22a97700901ba5e8bf8db68056a0d50f9440cae | ≥ 74ea66d4ca061a3cd4c0e924e51b60e924644852, < de5bd24197bd9ee37ec1e379a3d882bbd15c5065 | ≥ 74ea66d4ca061a3cd4c0e924e51b60e924644852, < 8ea0e7b3d7b8f2f0fc9db491ff22a0abe120801c | ≥ 74ea66d4ca061a3cd4c0e924e51b60e924644852, < 9b88a7c4584ba67267a051069b8abe44fc9595b2 | ≥ 74ea66d4ca061a3cd4c0e924e51b60e924644852, < 4410dba9807a17a93f649a9f5870ceaf30a675a3 | ≥ 74ea66d4ca061a3cd4c0e924e51b60e924644852, < b06f388994500297bb91be60ffaf6825ecfd2afe | 4.6
  • linux_kernel≥ 4.6, < 6.1.129 | ≥ 6.2, < 6.6.78 | ≥ 6.7, < 6.12.14 | ≥ 6.13, < 6.13.3
Debian1 product
  • linux< 6.1.129-1 | < 6.12.15-1

3 vendors · 138 products

References

38 links
Show all 38 references