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2021-10 Security Bulletin: SRC Series: NETCONF over SSH allows negotiation of weak ciphers (CVE-2021-31352)

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Article ID: JSA11217 SECURITY_ADVISORIES Last Updated: 13 Oct 2021Version: 1.0
Product Affected:
This issue affects SRC Series.
Problem:

An Information Exposure vulnerability in Juniper Networks SRC Series devices configured for NETCONF over SSH permits the negotiation of weak ciphers, which could allow a remote attacker to obtain sensitive information. A remote attacker with read and write access to network data could exploit this vulnerability to display plaintext bits from a block of ciphertext and obtain sensitive information.

This issue affects all Juniper Networks SRC Series versions prior to 4.13.0-R6.

A sample configuration of NETCONF over SSH is shown below:

netconf {
  ssh {
    port 830;
  }
}
 

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-2021-31352.
 

Solution:

A hotfix has been created to resolve this issue. Contact Juniper Networks Technical Support to request the hotfix.

Weak ciphers are now disabled by default. Only the following ciphers and key-exchange (KEX) algorithms are now enabled by default:

  • Ciphers: chacha20-poly1305@openssh.com,aes128-ctr,aes192-ctr,aes256-ctr,aes128-gcm@openssh.com,aes256-gcm@openssh.com
  • KEX Algorithms: curve25519-sha256,curve25519-sha256@libssh.org,ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,diffie-hellman-group-exchange-sha256,diffie-hellman-group16-sha512,diffie-hellman-group18-sha512,diffie-hellman-group14-sha256,diffie-hellman-group14-sha1


Note: After upgrading to a fixed release, any manually configured weak ciphers or KEX algorithms for NETCONF will be retained. Administrators should reset their cipher configuration by typing:

root@src# delete system services netconf ssh
root@src# commit
Stopping NETCONF/SSH:
commit complete.
root@src# set system services netconf ssh


This issue is being tracked as 1568322.
 

Workaround:
There are no viable workarounds for this issue.

 
Implementation:
Software releases or updates are available for download at https://support.juniper.net/support/downloads/
 
Modification History:
2021-10-13: Initial Publication.

CVSS Score:
5.3 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N)
Severity Level:
Medium
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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