CVE-2021-31354

An Out Of Bounds (OOB) access vulnerability in the handling of responses by a Juniper Agile License (JAL) Client in Juniper Networks Junos OS and Junos OS Evolved, configured in Network Mode (to use Juniper Agile License Manager) may allow an attacker to cause a partial Denial of Service (DoS), or lead to remote code execution (RCE). The vulnerability exists in the packet parsing logic on the client that processes the response from the server using a custom protocol. An attacker with control of a JAL License Manager, or with access to the local broadcast domain, may be able to spoof a new JAL License Manager and/or craft a response to the Junos OS License Client, leading to exploitation of this vulnerability. This issue only affects Junos systems configured in Network Mode. Systems that are configured in Standalone Mode (the default mode of operation for all systems) are not vulnerable to this issue. This issue affects: Juniper Networks Junos OS: 19.2 versions prior to 19.2R3-S3; 19.3 versions prior to 19.3R3-S3; 20.1 versions prior to 20.1R2-S2, 20.1R3-S1; 20.2 versions prior to 20.2R3-S2; 20.3 versions prior to 20.3R3; 20.4 versions prior to 20.4R3; 21.1 versions prior to 21.1R2. Juniper Networks Junos OS Evolved: version 20.1R1-EVO and later versions, prior to 21.2R2-EVO. This issue does not affect Juniper Networks Junos OS versions prior to 19.2R1.

Weakness

The product reads data past the end, or before the beginning, of the intended buffer.

Affected Software

Potential Mitigations

• Assume all input is malicious. Use an “accept known good” input validation strategy, i.e., use a list of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does.
• When performing input validation, consider all potentially relevant properties, including length, type of input, the full range of acceptable values, missing or extra inputs, syntax, consistency across related fields, and conformance to business rules. As an example of business rule logic, “boat” may be syntactically valid because it only contains alphanumeric characters, but it is not valid if the input is only expected to contain colors such as “red” or “blue.”
• Do not rely exclusively on looking for malicious or malformed inputs. This is likely to miss at least one undesirable input, especially if the code’s environment changes. This can give attackers enough room to bypass the intended validation. However, denylists can be useful for detecting potential attacks or determining which inputs are so malformed that they should be rejected outright.
• To reduce the likelihood of introducing an out-of-bounds read, ensure that you validate and ensure correct calculations for any length argument, buffer size calculation, or offset. Be especially careful of relying on a sentinel (i.e. special character such as NUL) in untrusted inputs.

Related Attack Patterns

• https://cwe.mitre.org/data/definitions/540.html

References

• https://kb.juniper.net/JSA11219