CVE-2024-21587
Juniper Junos 20.4 … 23.2
Raw vector
CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:HSummary
CVE-2024-21587 is a medium-severity Improper Handling of Exceptional Conditions (CWE-755) vulnerability in Juniper Junos. Its CVSS base score is 6.5 (Medium).
Operationally, exploitation aligns with the MITRE ATT&CK technique Application or System Exploitation (T1499.004); ranked at the 20th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.
OWASP Top 10 for Web (2025)
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2024-19235
Vulnerability Data
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…
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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.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise TechniquesAI
Why these techniques?
The vulnerability enables an adjacent attacker to exploit improper exception handling in bbe-smgd by repeatedly flapping DHCP subscriber sessions, causing a memory leak that leads to denial of service through application exploitation.
CVEs Like This One
Affected Assets
Mitigating Controls
Control response
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- 1 hardening rule · 1 OS baseline
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Likely Mitigating Controls AI
Per-CVE control mapping for this CVE has not run yet; the list below is derived from the weakness types (CWEs) cited in the NVD entry.
Provides defined handling (alert and additional actions) for the exceptional condition of audit logging failure.
Supplies a concrete handling action (safe mode) for exceptional conditions, mitigating risks from improper or absent handling that could allow continued attacks.
By preparing users for contingency scenarios, the control promotes proper handling of exceptional conditions instead of default or unsafe behaviors.
An updated contingency plan defines current actions for exceptional conditions, reducing the window for attackers to exploit improper handling leading to system failure.
Procedures ensure proper handling of exceptional conditions to support effective incident response.
Incident response testing confirms proper handling of exceptional conditions to limit exploit impact.
Gives users guidance on incident handling, reducing improper handling of exceptional conditions that could stem from exploited weaknesses.
Enforces structured response to exceptional conditions so the system cannot remain in an unsafe state.
Mitigating Controls (NIST CSF 2.0) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.
Secure SDLC practices explicitly require proper exception and error handling during design and coding.
Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.
Security testing in development and acceptance verifies correct handling of exceptional conditions.
Documented operating procedures may specify exception handling but do not guarantee implementation.
Logging captures unhandled exceptions, aiding detection but not preventing the weakness.
Monitoring can surface unhandled exceptions but does not enforce proper handling.
Secure SDLC mandates exception-handling requirements and testing that directly prevent improper handling of exceptional conditions.
Application security requirements explicitly include handling of error and exceptional conditions.