CVE-2023-36843

An Improper Handling of Inconsistent Special Elements vulnerability in the Junos Services Framework (jsf) module of Juniper Networks Junos OS allows an unauthenticated network based attacker to cause a crash in the Packet Forwarding Engine (pfe) and thereby resulting in a Denial of Service (DoS).

Upon receiving malformed SSL traffic, the PFE crashes. A manual restart will be needed to recover the device.

This issue only affects devices with Juniper Networks Advanced Threat Prevention (ATP) Cloud enabled with Encrypted Traffic Insights (configured via ‘security-metadata-streaming policy’).

This issue affects Juniper Networks Junos OS:

• All versions prior to 20.4R3-S8, 20.4R3-S9;
• 21.1 version 21.1R1 and later versions;
• 21.2 versions prior to 21.2R3-S6;
• 21.3 versions prior to 21.3R3-S5;
• 21.4 versions prior to 21.4R3-S5;
• 22.1 versions prior to 22.1R3-S4;
• 22.2 versions prior to 22.2R3-S2;
• 22.3 versions prior to 22.3R2-S2, 22.3R3;
• 22.4 versions prior to 22.4R2-S1, 22.4R3;

Weakness

The product does not properly handle input in which an inconsistency exists between two or more special characters or reserved words.

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.

References

• https://supportportal.juniper.net/JSA73174
• https://supportportal.juniper.net/JSA73174