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Out-of-Cycle Security Bulletin: Junos: Crafted TCP packet can lead to kernel crash



Article ID: JSA10550 SECURITY_ADVISORIES Last Updated: 09 May 2013Version: 3.0
Legacy Advisory Id:
Product Affected:
This issue can affect any device running Junos OS 7.6R1 or later configured with open TCP ports (eg. telnet, SSH, BGP, etc.) allowing incoming TCP connections to reach the RE.

The Junos kernel may crash when a specifically crafted TCP packet is received by the Routing Engine (RE) on a listening TCP port. TCP traffic traversing the device will not trigger this crash. Only TCP packets destined to the device itself, successfully reaching the RE through existing edge and control plane filtering, will be able to cause the crash. This issue can be triggered by both IPv4 and IPv6 TCP packets destined to the RE.

This issue was found during internal product security testing.

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

This issue only affects devices running Junos OS 7.6R1 and later. No other Juniper Networks products or platforms are affected by this issue.

All Junos OS software releases built on or after 2013-01-17 have fixed this specific issue. Releases containing the fix specifically include: 10.4S12, 10.4R13, 11.4R6-S1, 12.1R4-S3, 12.1R5, 12.2R2-S2, 12.2R3, 12.3R1, and all subsequent releases (i.e. all releases built after 12.3R1). In addition, all JTAC Recommended Releases listed in KB21476 have been updated to include this fix.

Customers can confirm the build date of any Junos OS release by issuing the command 'show version detail'.

This issue is being tracked as PR 839412 and is visible on the Customer Support website.

KB16765 - "In which releases are vulnerabilities fixed?" describes which release vulnerabilities are fixed as per our End of Engineering and End of Life support policies.


The impact of the specially crafted TCP packet successfully making it's way to a listening port on the RE is a kernel crash and switchover (or reboot on single RE systems).

Standard security best common practices (BCPs) can be employed, using access lists or firewall filters deployed on both the edge and control plane in combination with source address anti-spoofing, and where applicable, TTL security mechanisms to significantly reduce the risk of malicious exploit by limiting access to the device only from valid, trusted hosts. Features like uRPF and TTL Security (see sample macro below), or simply applying input firewall filters at the peering interfaces which discard traffic sourced from internal prefixes, will aid customers in protecting their network from remote attacks relying on spoofed source addresses. Note that while it's possible to use source routing to bypass uRPF, source routing is disabled by default in all recent Junos releases.

How to obtain fixed software:

Security vulnerabilities in Junos are fixed in the next available Maintenance Release of each supported Junos version. In some cases, a Maintenance Release is not planned to be available in an appropriate time-frame. For these cases, Service Releases are made available in order to be more timely. Security Advisory and Security Notices will indicate which Maintenance and Service Releases contain fixes for the issues described. Upon request to JTAC, customers will be provided download instructions for a Service Release. Although Juniper does not provide formal Release Note documentation for a Service Release, a list of "PRs fixed" can be provided on request.
CVSS Score:
7.8 (AV:N/AC:L/Au:N/C:N/I:N/A:C)
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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