CVE-2024-39554

A Concurrent Execution using Shared Resource with Improper Synchronization (Race Condition) vulnerability the

Routing Protocol Daemon (rpd)

of Juniper Networks Junos OS and Juniper Networks Junos OS Evolved allows an unauthenticated, network-based attacker to inject incremental routing updates when BGP multipath is enabled, causing rpd to crash and restart, resulting in a Denial of Service (DoS). Since this is a timing issue (race condition), the successful exploitation of this vulnerability is outside the attackers control.  However, continued receipt and processing of this packet may create a sustained Denial of Service (DoS) condition.

On all Junos OS and Junos OS Evolved platforms with BGP multipath enabled, a specific multipath calculation removes the original next hop from the multipath lead routes nexthop-set. When this change happens, multipath relies on certain internal timing to record the update.  Under certain circumstance and with specific timing, this could result in an rpd crash.

This issue only affects systems with BGP multipath enabled.

This issue affects:

Junos OS:

• All versions of 21.1
• from 21.2 before 21.2R3-S7,
• from 21.4 before 21.4R3-S6,
• from 22.1 before 22.1R3-S5,
• from 22.2 before 22.2R3-S3,
• from 22.3 before 22.3R3-S2,
• from 22.4 before 22.4R3,
• from 23.2 before 23.2R2.

Junos OS Evolved:

• All versions of 21.1-EVO,
• All versions of 21.2-EVO,
• from 21.4-EVO before 21.4R3-S6-EVO,
• from 22.1-EVO before 22.1R3-S5-EVO,
• from 22.2-EVO before 22.2R3-S3-EVO,
• from 22.3-EVO before 22.3R3-S2-EVO,
• from 22.4-EVO before 22.4R3-EVO,
• from 23.2-EVO before 23.2R2-EVO.

Versions of Junos OS before 21.1R1 are unaffected by this vulnerability. Versions of Junos OS Evolved before 21.1R1-EVO are unaffected by this vulnerability.

Weakness

The product contains a concurrent code sequence that requires temporary, exclusive access to a shared resource, but a timing window exists in which the shared resource can be modified by another code sequence operating concurrently.

Affected Software

Extended Description

A race condition occurs within concurrent environments, and it is effectively a property of a code sequence. Depending on the context, a code sequence may be in the form of a function call, a small number of instructions, a series of program invocations, etc. A race condition violates these properties, which are closely related:

A race condition exists when an “interfering code sequence” can still access the shared resource, violating exclusivity. The interfering code sequence could be “trusted” or “untrusted.” A trusted interfering code sequence occurs within the product; it cannot be modified by the attacker, and it can only be invoked indirectly. An untrusted interfering code sequence can be authored directly by the attacker, and typically it is external to the vulnerable product.

Potential Mitigations

• Minimize the usage of shared resources in order to remove as much complexity as possible from the control flow and to reduce the likelihood of unexpected conditions occurring.
• Additionally, this will minimize the amount of synchronization necessary and may even help to reduce the likelihood of a denial of service where an attacker may be able to repeatedly trigger a critical section (CWE-400).

Related Attack Patterns

• https://cwe.mitre.org/data/definitions/26.html
• https://cwe.mitre.org/data/definitions/29.html

References

• https://supportportal.juniper.net/JSA83014
• https://supportportal.juniper.net/JSA83014