CVE-2023-36838

An Out-of-bounds Read vulnerability in the flow processing daemon (flowd) of Juniper Networks Junos OS on SRX Series allows a local, authenticated attacker with low privileges, to cause a Denial of Service (DoS).

If a low privileged user executes a specific CLI command, flowd which is responsible for traffic forwarding in SRX crashes and generates a core dump. This will cause temporary traffic interruption until the flowd process is restarted automatically. Continued execution of this command will lead to a sustained DoS.

This issue affects Juniper Networks Junos OS on SRX Series: All versions prior to 20.2R3-S7; 20.3 version 20.3R1 and later versions; 20.4 versions prior to 20.4R3-S6; 21.1 versions prior to 21.1R3-S5; 21.2 versions prior to 21.2R3-S4; 21.3 versions prior to 21.3R3-S4; 21.4 versions prior to 21.4R3-S3; 22.1 versions prior to 22.1R3-S1; 22.2 versions prior to 22.2R3; 22.3 versions prior to 22.3R2; 22.4 versions prior to 22.4R1-S1, 22.4R2.

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://supportportal.juniper.net/JSA71645
• https://supportportal.juniper.net/JSA71645