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2021-07 Security Bulletin: Junos OS: FreeBSD-EN-18:11.listen: TCP during bind, listen or connect and UDP during bind may experience Denial of Service for IPv6 based sockets. (CVE-2018-6925)



Article ID: JSA11178 SECURITY_ADVISORIES Last Updated: 14 Jul 2021Version: 2.0
Product Affected:
This issue affects Junos OS 12.3, 15.1, 17.3, 17.4, 18.1, 18.2, 18.3, 18.4, 19.1, 19.2, 19.3, 19.4.

In Juniper Networks Junos OS there are various cases in the IPv6 socket code where the protocol control block's state flags are modified during a syscall, but are not restored if the operation fails. This can leave the control block in an inconsistent state. The protocol control block is a structure that maintains the Network Layer state for various sockets. There are various state flags that must be properly maintained to keep the structure consistent. Due to improper maintenance of the IPv6 protocol control block flags through various failure paths, an unprivileged authenticated local user may be able to cause a NULL pointer dereference causing the kernel to crash allowing an attacker to cause a Denial of Service (DoS) condition.

This issue only impacts IPv6 TCP/UDP traffic destined to the device; for example: BGP, Netconf, telnet, SSH, HTTP, HTTPS, etc.

This issue can occur on any interface of a device.

This issue does not affect any other IPv6 Internet Protocol (IP) traffic.

This issue does not impact any IPv4 traffic.

This issue affects:

Juniper Networks Junos OS

  • 12.3 versions prior to 12.3R12-S19;
  • 15.1 versions prior to 15.1R7-S10;
  • 17.3 versions prior to 17.3R3-S12;
  • 17.4 versions prior to 17.4R2-S13, 17.4R3-S5;
  • 18.1 versions prior to 18.1R3-S13;
  • 18.2 versions prior to 18.2R3-S8;
  • 18.3 versions prior to 18.3R3-S5;
  • 18.4 versions prior to 18.4R3-S8;
  • 19.1 versions prior to 19.1R3;
  • 19.2 versions prior to 19.2R1-S7, 19.2R2;
  • 19.3 versions prior to 19.3R2-S6, 19.3R3;
  • 19.4 versions prior to 19.4R1-S4, 19.4R2.

'family inet6' must be configured on the device.

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

This issue was discovered during external security research.

This issue has been assigned CVE-2018-6925.


The following software releases have been updated to resolve this specific issue: Junos OS 12.3R12-S19, 15.1R7-S10, 17.3R3-S12, 17.4R2-S13, 17.4R3-S5, 18.1R3-S13, 18.2R3-S8, 18.3R3-S5, 18.4R3-S8, 19.1R3, 19.2R1-S7, 19.2R2, 19.3R2-S6, 19.3R3, 19.4R1-S4, 19.4R2, 20.1R1, and all subsequent releases.

This issue is being tracked as 1472367.


There are no viable workarounds for this issue.

To reduce the risk of malicious exploitation, use access lists or firewall filters to limit CLI access to the device only from trusted, administrative networks or hosts. Additionally, limit access to the Junos OS shell to only trusted system administrators.

Software releases or updates are available for download at
Modification History:
2021-07-14: Initial Publication.

CVSS Score:
5.5 (CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H)
Severity Level:
Severity Assessment:
Information for how Juniper Networks uses CVSS can be found at KB 16446 "Common Vulnerability Scoring System (CVSS) and Juniper's Security Advisories."

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