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



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

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.


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:,aes128-ctr,aes192-ctr,aes256-ctr,,
  • KEX Algorithms: curve25519-sha256,,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
commit complete.
root@src# set system services netconf ssh

This issue is being tracked as 1568322.

There are no viable workarounds for this issue.

Software releases or updates are available for download at
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:
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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