Junos OS: Out-of-memory condition and crashes can occur after executing a certain CLI command repeatedly

Description

A vulnerability in Juniper Networks Junos OS caused by Missing Release of Memory after Effective Lifetime leads to a memory leak each time the CLI command 'show system connections extensive' is executed. The amount of memory leaked on each execution depends on the number of TCP connections from and to the system. Repeated execution will cause more memory to leak and eventually daemons that need to allocate additionally memory and ultimately the kernel to crash, which will result in traffic loss. Continued execution of this command will cause a sustained Denial of Service (DoS) condition. An administrator can use the following CLI command to monitor for increase in memory consumption of the netstat process, if it exists: user@junos> show system processes extensive | match "username|netstat" PID USERNAME PRI NICE SIZE RES STATE C TIME WCPU COMMAND 21181 root 100 0 5458M 4913M CPU3 2 0:59 97.27% netstat The following log message might be observed if this issue happens: kernel: %KERN-3: pid 21181 (netstat), uid 0, was killed: out of swap space This issue affects Juniper Networks Junos OS 18.2 versions prior to 18.2R2-S8, 18.2R3-S7. 18.3 versions prior to 18.3R3-S4; 18.4 versions prior to 18.4R1-S8, 18.4R2-S6, 18.4R3-S7; 19.1 versions prior to 19.1R1-S6, 19.1R2-S2, 19.1R3-S4; 19.2 versions prior to 19.2R1-S6, 19.2R3-S2; 19.3 versions prior to 19.3R2-S6, 19.3R3-S1; 19.4 versions prior to 19.4R1-S4, 19.4R2-S3, 19.4R3-S1; 20.1 versions prior to 20.1R2; 20.2 versions prior to 20.2R2-S1, 20.2R3; 20.3 versions prior to 20.3R1-S1, 20.3R2; This issue does not affect Juniper Networks Junos OS versions prior to 18.2R1.

Scores

EPSS (exploitation in 30 days)

0.25% · top 84% of all CVEs (6 Nov 2026)

The list uses the assigner's score when there is one, then CISA's, then NVD's: Medium 5.5.

Weakness

• CWE-401 Missing Release of Memory after Effective Lifetime (opens in a new tab)All about CWE-401 and its CVEs

Affected products

• Juniper Networks · Junos OS

  • unaffected unspecified – < 18.2R1
  • affected 18.3 – < 18.3R3-S4
  • affected 18.4 – < 18.4R1-S8, 18.4R2-S6, 18.4R3-S7
  • affected 19.1 – < 19.1R1-S6, 19.1R2-S2, 19.1R3-S4
  • affected 19.2 – < 19.2R1-S6, 19.2R3-S2
  • affected 19.3 – < 19.3R2-S6, 19.3R3-S1
  • affected 19.4 – < 19.4R1-S4, 19.4R2-S3, 19.4R3-S1
  • affected 20.1 – < 20.1R2
  • affected 20.2 – < 20.2R2-S1, 20.2R3
  • affected 20.3 – < 20.3R1-S1, 20.3R2
  • affected 18.2 – < 18.2R2-S8, 18.2R3-S7

What to do

Solution: The following software releases have been updated to resolve this specific issue: 18.2R2-S8, 18.2R3-S7, 18.3R3-S4, 18.4R1-S8, 18.4R2-S6, 18.4R3-S7, 19.1R1-S6, 19.1R2-S2, 19.1R3-S4, 19.2R1-S6, 19.2R3-S2, 19.3R2-S6, 19.3R3-S1, 19.3R3-S2, 19.4R1-S4, 19.4R2-S3, 19.4R3-S1, 20.1R2, 20.2R2-S1, 20.2R3, 20.3R1-S1, 20.3R2, 20.4R1, and all subsequent releases.

Workaround: Please use 'show system connections' (without extensive) and restrict access to 'show system connections extensive'. To recover please use: request system process terminate <PID> with the PID for the netstat process from the output of 'show system processes extensive'.

Exploitation: Juniper SIRT is not aware of any malicious exploitation of this vulnerability.

References (1)

• https://kb.juniper.net/JSA11195 (opens in a new tab)x_refsource_CONFIRMx_transferred

Sources

The same CVE in the primary databases and aggregators, to check against.

• CVE.org record (opens in a new tab)
• CVE List JSON (GitHub) (opens in a new tab)
• NVD (opens in a new tab)
• FIRST EPSS (opens in a new tab)
• OSV.dev (opens in a new tab)
• GitHub Advisories (opens in a new tab)
• CIRCL Vulnerability-Lookup (opens in a new tab)

Badge for a README or a ticket

[![CVE-2021-0293](https://trackcve.app/badge/CVE-2021-0293.svg)](https://trackcve.app/cve/CVE-2021-0293)

Record last updated 16 Sept 2024, 22:40 UTC.