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2012-04 Security Bulletin: Junos: High rate of HTTP connections can send httpd into a spinlock



Article ID: JSA10505 SECURITY_ADVISORIES Last Updated: 09 May 2013Version: 1.0
Legacy Advisory Id:
Product Affected:
This is a "day one" issue that can affect all Junos routers with J-Web enabled.

A high rate of inbound HTTP connections over an extended period of time may trap the httpd process into a spinlock, causing high CPU utilization. CPU load continues even after the stream of connection attempts is terminated. The process must be killed from the shell to reduce the CPU load.

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

No other Juniper Networks products or platforms are affected by this issue.

Resource locking of reentrant signal handling for multiple processes has been rewritten to be more robust and handle exceptional cases of continuous heavy load on the httpd daemon.

All Junos OS software releases built on or after 2012-03-29 have fixed this specific issue. Releases containing the fix specifically include: 10.4S9, 11.2R6, 11.4R2-S1, 12.1R1, and all subsequent releases (i.e. all releases built after 12.1R1).

This issue is being tracked as PR 693434 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.


Disable J-Web, or allow access to J-Web only from trusted networks.

Alternately, depending on configuration and topology, apply a policer at the edge or on the control plane (lo0) to rate-limit inbound connections to TCP port 80. Note that the typical side effects of applying rate limiting to services (eg. increased risk of successful DoS attack) also apply to inbound J-Web connections, so care should be taken before making changes to control plane protection firewall filters. See RFC 6192 on guidance for protecting the router's control plane.

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:
5.0 (AV:N/AC:L/Au:N/C:N/I:N/A:P)
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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