CVE-2024-21598

An Improper Validation of Syntactic Correctness of Input vulnerability in the Routing Protocol Daemon (rpd) of Juniper Networks Junos OS and Junos OS Evolved allows a network-based, unauthenticated attacker to cause a Denial of Service (DoS).

If a BGP update is received over an established BGP session which contains a tunnel encapsulation attribute with a specifically malformed TLV, rpd will crash and restart.

This issue affects Juniper Networks Junos OS:

• 20.4 versions 20.4R1 and later versions earlier than 20.4R3-S9;
• 21.2 versions earlier than 21.2R3-S7;
• 21.3 versions earlier than 21.3R3-S5;
• 21.4 versions earlier than 21.4R3-S5;
• 22.1 versions earlier than 22.1R3-S4;
• 22.2 versions earlier than 22.2R3-S3;
• 22.3 versions earlier than 22.3R3-S1;
• 22.4 versions earlier than 22.4R3;
• 23.2 versions earlier than 23.2R1-S2, 23.2R2;

Junos OS Evolved:

• 20.4-EVO versions 20.4R1-EVO and later versions earlier than 20.4R3-S9-EVO;
• 21.2-EVO versions earlier than 21.2R3-S7-EVO;
• 21.3-EVO versions earlier than 21.3R3-S5-EVO;
• 21.4-EVO versions earlier than 21.4R3-S5-EVO;
• 22.1-EVO versions earlier than 22.1R3-S4-EVO;
• 22.2-EVO versions earlier than 22.2R3-S3-EVO;
• 22.3-EVO versions earlier than 22.3R3-S1-EVO;
• 22.4-EVO versions earlier than 22.4R3-EVO;
• 23.2-EVO versions earlier than 23.2R1-S2-EVO, 23.2R2-EVO;

This issue does not affect Juniper Networks

• Junos OS versions earlier than 20.4R1;
• Junos OS Evolved versions earlier than 20.4R1-EVO.

This is a related but separate issue than the one described in JSA79095.

Weakness

The product receives input that is expected to be well-formed - i.e., to comply with a certain syntax - but it does not validate or incorrectly validates that the input complies with the syntax.

Affected Software

Extended Description

Often, complex inputs are expected to follow a particular syntax, which is either assumed by the input itself, or declared within metadata such as headers. The syntax could be for data exchange formats, markup languages, or even programming languages. When untrusted input is not properly validated for the expected syntax, attackers could cause parsing failures, trigger unexpected errors, or expose latent vulnerabilities that might not be directly exploitable if the input had conformed to the syntax.

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.

Related Attack Patterns

• https://cwe.mitre.org/data/definitions/66.html
• https://cwe.mitre.org/data/definitions/676.html

References

• http://supportportal.juniper.net/JSA75739
• https://www.first.org/cvss/calculator/4.0#CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:L
• http://supportportal.juniper.net/JSA75739
• https://www.first.org/cvss/calculator/4.0#CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:L