CVE-2024-21587VulnerabilityPublished 12 Jan 2024Updated 3 Jun 2025

CVE-2024-21587: Juniper Networks Junos OS · Improper Handling of Exceptional Conditions

Affects Juniper Networks Junos OSSource CVE Database V5

Not known to be exploited · CVSS 6.5 Medium.

Data as of 26 Oct 2026, 06:26 UTC

CVSS 3.1 base score

6.5Medium

How severe the flaw is on the 0–10 CVSS scale.

EPSS: 0.2% chance of exploitation in 30 days – higher than 20% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.

CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Attack Vector: Adjacent
Attack Complexity: Low
Privileges Required: None
User Interaction: None
Scope: Unchanged
Confidentiality: None
Integrity: None
Availability: High

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Adjacent: The vulnerable component is bound to the network stack, but the attack is limited at the protocol level to a logically adjacent topology. This can mean an attack must be launched from the same shared physical (e.g., Bluetooth or IEEE 802.11) or logical (e.g., local IP subnet) network, or from within a secure or otherwise limited administrative domain (e.g., MPLS, secure VPN to an administrative network zone).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files to carry out an attack.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
Scope: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: None: There is no loss of confidentiality within the impacted component.
Integrity: None: There is no loss of integrity within the impacted component.
Availability: High: There is total loss of availability, resulting in the attacker being able to fully deny access to resources in the impacted component; this loss is either sustained (while the attacker continues to deliver the attack) or persistent (the condition persists even after the attack has completed). Alternatively, the attacker has the ability to deny some availability, but the loss of availability presents a direct, serious consequence to the impacted component (e.g., the attacker cannot disrupt existing connections, but can prevent new connections; the attacker can repeatedly exploit a vulnerability that, in each instance of a successful attack, leaks a only small amount of memory, but after repeated exploitation causes a service to become completely unavailable).

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 12 Jan 2024
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 2026-10-26.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Affected software

Product	Affected	Fixed in
Juniper Networks Junos OS	Affected =0 =21.2 =21.3 =21.4 =22.1 =22.2 =22.3 =22.4 =23.2	Fixed in–

AI-suggested

1. Immediate mitigation involves disabling BFD liveness detection for DHCP subscribers if feasible, as systems without BFD enabled are not vulnerable. 2. Apply the latest Junos OS patches from Juniper Networks that address this vulnerability. Ensure all MX Series routers are updated to versions at or beyond the fixed releases (e.g., 20.4R3-S9, 21.2R3-S7, 21.3R3-S5, etc.). 3. Implement network segmentation and access controls to limit adjacency access to the MX Series routers, reducing the attack surface. 4. Monitor the memory usage of the bbe-smgd process regularly using 'show system processes extensive' to detect early signs of memory leaks. 5. Automate alerts for abnormal memory growth in bbe-smgd to enable proactive response before service degradation occurs. 6. Prepare operational procedures for rapid restart of the bbe-smgd daemon to restore service if memory exhaustion is detected. 7. Conduct configuration reviews to ensure that only necessary features are enabled and that BFD liveness detection is used judiciously. 8. Engage with Juniper support for guidance and to verify patch applicability in complex network environments.

Description

An Improper Handling of Exceptional Conditions vulnerability in the broadband edge subscriber management daemon (bbe-smgd) of Juniper Networks Junos OS on MX Series allows an attacker directly connected to the vulnerable system who repeatedly flaps DHCP subscriber sessions to cause a slow memory leak, ultimately leading to a Denial of Service (DoS). Memory can only be recovered by manually restarting bbe-smgd. This issue only occurs if BFD liveness detection for DHCP subscribers is enabled. Systems without BFD liveness detection enabled are not vulnerable to this issue. Indication of the issue can be observed by periodically executing the 'show system processes extensive' command, which will indicate an increase in memory allocation for bbe-smgd. A small amount of memory is leaked every time a DHCP subscriber logs in, which will become visible over time, ultimately leading to memory starvation.user@junos> show system processes extensive | match bbe-smgd 13071 root 24 0 415M 201M select 0 0:41 7.28% bbe-smgd{bbe-smgd} 13071 root 20 0 415M 201M select 1 0:04 0.00% bbe-smgd{bbe-smgd} ... user@junos> show system processes extensive | match bbe-smgd 13071 root 20 0 420M 208M select 0 4:33 0.10% bbe-smgd{bbe-smgd} 13071 root 20 0 420M 208M select 0 0:12 0.00% bbe-smgd{bbe-smgd} ... This issue affects Juniper Networks Junos OS on MX Series: * All 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-S2; * 22.4 versions earlier than 22.4R2-S2, 22.4R3; * 23.2 versions earlier than 23.2R1-S1, 23.2R2.

Impact

For European organizations, especially those relying on Juniper MX Series routers for broadband edge subscriber management, this vulnerability poses a risk of service disruption. The slow memory leak can degrade router performance over time, leading to denial of service conditions that interrupt DHCP subscriber session management. This can affect ISPs, telecommunications providers, and enterprises with large subscriber bases or critical network infrastructure. The impact includes potential loss of connectivity for end-users, degraded network reliability, and operational overhead due to the need for manual intervention to restart the affected daemon. Given that the attack requires adjacency (direct network access) and the presence of BFD liveness detection enabled for DHCP subscribers, the threat is more pronounced in environments where these configurations are common. Disruptions in broadband edge services can have cascading effects on business operations, customer satisfaction, and regulatory compliance, particularly in sectors with stringent uptime requirements such as finance, healthcare, and public services.

Summary

CVE-2024-21587 is a vulnerability in Juniper Networks Junos OS specifically affecting the MX Series routers. The flaw resides in the broadband edge subscriber management daemon (bbe-smgd), which is responsible for managing DHCP subscriber sessions. When Bidirectional Forwarding Detection (BFD) liveness detection for DHCP subscribers is enabled, an attacker who has direct network access to the vulnerable system can repeatedly flap DHCP subscriber sessions. This action causes a slow memory leak within the bbe-smgd process. Over time, the leaked memory accumulates, leading to memory starvation and ultimately causing a Denial of Service (DoS) condition. The memory leak is subtle and incremental, observable by monitoring the memory usage of bbe-smgd via the 'show system processes extensive' command, which will show a gradual increase in memory allocation. The leaked memory is only recoverable by manually restarting the bbe-smgd daemon, which disrupts subscriber management services. This vulnerability affects multiple versions of Junos OS prior to specific patched releases across versions 20.4 through 23.2. The CVSS v3.1 base score is 6.5 (medium severity), reflecting that the attack vector is adjacent network (AV:A), requires no privileges (PR:N), no user interaction (UI:N), and impacts availability (A:H) without affecting confidentiality or integrity. No known exploits are currently reported in the wild. The vulnerability is categorized under CWE-755, indicating improper handling of exceptional conditions, specifically related to resource management in the daemon.

CWE-755Improper Handling of Exceptional Conditions (opens in a new tab)
Class weaknessLikelihood of exploit: MediumOWASP Top 10 A10:2025: Mishandling of Exceptional Conditions (opens in a new tab)
The product does not handle or incorrectly handles an exceptional condition.
MITRE discourages mapping vulnerabilities to this broad entry; the root cause is usually a more specific weakness.
OWASP Cheat Sheets
Logging (opens in a new tab)
Error Handling (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

Community reviews

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 4 Jul 2025, 14:41 UTC

WeaknessesCWE-755

Technical details

References

Community reviews

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