An Improper Neutralization of CRLF Sequences in HTTP Headers ('HTTP Response Splitting') weakness in J-web of Juniper Networks Junos OS leads to buffer overflows, segment faults, or other impacts, which allows an attacker to modify the integrity of the device and exfiltration information from the device without authentication. The weakness can be exploited to facilitate cross-site scripting (XSS), cookie manipulation (modifying session cookies, stealing cookies) and more. This weakness can also be exploited by directing a user to a seemingly legitimate link from the affected site. The attacker requires no special access or permissions to the device to carry out such attacks.

This issue affects:

Juniper Networks Junos OS:

• 18.1 versions prior to 18.1R3-S11;
• 18.2 versions prior to 18.2R3-S5;
• 18.3 versions prior to 18.3R2-S4, 18.3R3-S3;
• 18.4 versions prior to 18.4R2-S5, 18.4R3-S3;
• 19.1 versions prior to 19.1R2-S2, 19.1R3-S2;
• 19.2 versions prior to 19.2R1-S5, 19.2R2;
• 19.3 versions prior to 19.3R3;
• 19.4 versions prior to 19.4R1-S3, 19.4R2, 19.4R3;
• 20.1 versions prior to 20.1R1-S2, 20.1R2.

• This issue does not affect Juniper Networks Junos OS versions prior to 18.1R1.

The following minimal configuration is necessary:

or

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

This issue was found during internal product security testing or research.

This issue has been assigned  CVE-2021-0268 .

The following software releases have been updated to resolve this specific issue: 18.1R3-S11, 18.2R3-S5, 18.3R2-S4, 18.3R3-S3, 18.4R2-S5, 18.4R3-S3, 19.1R2-S2, 19.1R3-S2, 19.2R1-S5, 19.2R2, 19.3R3, 19.4R1-S3, 19.4R2, 19.4R3, 20.1R1-S2, 20.1R2, 20.2R1, and all subsequent releases.

This issue is being tracked as  1503569 .

Software releases or updates are available for download at https://support.juniper.net/support/downloads/

There are no viable workarounds for this issue other than disabling the J-Web service.

To reduce the risk of exploitation utilize common security BCPs to limit the exploitable surface by limiting access to network and device to trusted systems, administrators, networks and hosts.

2021-04-14: Initial Publication.

• KB16613: Overview of the Juniper Networks SIRT Quarterly Security Bulletin Publication Process [juniper.net]
• KB16765: In which releases are vulnerabilities fixed? [juniper.net]
• KB16446: Common Vulnerability Scoring System (CVSS) and Juniper's Security Advisories [juniper.net]
• Report a Security Vulnerability - How to Contact the Juniper Networks Security Incident Response Team
• CVE-2021-0268 at cve.mitre.org

The Juniper SIRT wishes to thank Luca Ercoli for responsibly reporting one of the issues resolved in this update.