Cyber Resilience

CVE-2024-21591

Memory Safety in Juniper Junos ≤ 20.4

Public PoCMemory Safety
Published
12 January 2024
Modified
17 June 2026
Patch / advisory
View advisory
CVSS Score v3.1 9.8
Click a component to see what it means
Raw vectorCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
EPSS Score 0.18 97th percentile
Risk Priority 85 floored blend · peak EPSS

Summary

CVE-2024-21591 is a critical-severity Out-of-bounds Write (CWE-787) vulnerability in Juniper Junos. Its CVSS base score is 9.8 (Critical).

Operationally, exploitation aligns with the MITRE ATT&CK technique Exploitation for Privilege Escalation (T1068); ranked in the top 3% of CVEs by exploit likelihood; it is not currently listed in the CISA KEV catalog; a public proof-of-concept is referenced.

The strongest mitigations our analysis identified map to SA-11 (Developer Testing and Evaluation) and SA-15 (Development Process, Standards, and Tools) — see the control section below for these in your framework.

Deeper analysis AI-assisted summary

Synthesised by an AI model from the NVD description and linked references — a reading aid, not an authoritative source.

An Out-of-bounds Write vulnerability exists in the J-Web component of Juniper Networks Junos OS on SRX Series and EX Series devices. It stems from use of an insecure function that permits overwriting of arbitrary memory. The flaw affects all Junos OS releases prior to 20.4R3-S9, 21.2R3-S7, 21.3R3-S5, 21.4R3-S5, 22.1R3-S4, 22.2R3-S3, 22.3R3-S2, and 22.4R2-S2/22.4R3, and carries a CVSS 3.1 score of 9.8.

An unauthenticated network-based attacker can send specially crafted requests to the J-Web interface to trigger the flaw. Successful exploitation can result in a denial of service or full remote code execution with root privileges on the affected device.

Juniper’s advisory JSA75729 and the listed fixed releases indicate that mitigation requires upgrading to one of the patched Junos OS versions. No other workarounds are described in the supplied references.

EPSS for the CVE reached a peak of 0.2504 after disclosure before receding to the current value of 0.1669, indicating a measurable increase in observed exploitation interest following public release.

EU & UK References

Vulnerability Data

An Out-of-bounds Write vulnerability in J-Web of Juniper Networks Junos OS on SRX Series and EX Series allows an unauthenticated, network-based attacker to cause a Denial of Service (DoS), or Remote Code Execution (RCE) and obtain root privileges on the…

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device. This issue is caused by use of an insecure function allowing an attacker to overwrite arbitrary memory. This issue affects Juniper Networks Junos OS SRX Series and EX Series: * Junos OS versions earlier than 20.4R3-S9; * Junos OS 21.2 versions earlier than 21.2R3-S7; * Junos OS 21.3 versions earlier than 21.3R3-S5; * Junos OS 21.4 versions earlier than 21.4R3-S5; * Junos OS 22.1 versions earlier than 22.1R3-S4; * Junos OS 22.2 versions earlier than 22.2R3-S3; * Junos OS 22.3 versions earlier than 22.3R3-S2; * Junos OS 22.4 versions earlier than 22.4R2-S2, 22.4R3.

CWE(s)
CWE-787

Related Threats

MITRE ATT&CK Enterprise Techniques

T1068 Exploitation for Privilege Escalation Privilege Escalation
Adversaries may exploit software vulnerabilities in an attempt to elevate privileges.
attack.mitre.org →
T1190 Exploit Public-Facing Application Initial Access
Adversaries may attempt to exploit a weakness in an Internet-facing host or system to initially access a network.
attack.mitre.org →
T1203 Exploitation for Client Execution Execution
Adversaries may exploit software vulnerabilities in client applications to execute code.
attack.mitre.org →
T1210 Exploitation of Remote Services Lateral Movement
Adversaries may exploit remote services to gain unauthorized access to internal systems once inside of a network.
attack.mitre.org →
T1211 Exploitation for Stealth Stealth
Adversaries may exploit vulnerabilities to evade detection by hiding activity, suppressing logging, or operating within trusted or unmonitored components.
attack.mitre.org →
T1212 Exploitation for Credential Access Credential Access
Adversaries may exploit software vulnerabilities in an attempt to collect credentials.
attack.mitre.org →
Derived from this CVE’s CWE(s) via the direct CWE→ATT&CK cross-walk.

CVEs Like This One

CVE-2024-21594Same product: Juniper Junos
CVE-2023-44197Same product: Juniper Junos
CVE-2024-21596Same product: Juniper Junos
CVE-2023-44178Same product: Juniper Junos
CVE-2024-30394Same product: Juniper Junos
CVE-2023-44177Same product: Juniper Junos
CVE-2023-44176Same product: Juniper Junos
CVE-2023-22411Same product: Juniper Junos
CVE-2023-22404Same product: Juniper Junos
CVE-2023-22415Same product: Juniper Junos

Affected Assets

juniper
junos
20.4, 21.2, 21.3, 21.4, 22.1 · ≤ 20.4

Mitigating Controls

Mitigating Controls (NIST 800-53 r5) AI

SA-11 Developer Testing and Evaluation good match

Developer testing and evaluation (including fuzzing and bounds checks) finds out-of-bounds write flaws before deployment.

SA-15 Development Process, Standards, and Tools partial match

Requiring documented secure-development standards and tools can mandate bounds-checked coding practices that avoid the weakness.

SI-10 Information Input Validation partial match

Input validation can structurally reject or sanitize data that would otherwise trigger an out-of-bounds write.

SI-16 Memory Protection partial match

Memory-protection mechanisms limit the exploitability and blast radius of a successful out-of-bounds write.

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.

PR.PS-06 mostly match
prevents

Secure-development practices (static analysis, bounds checking, code review) are the primary means of preventing out-of-bounds writes.

ID.RA-01 partial match
prevents

Vulnerability scanning and recording can discover out-of-bounds write flaws so they can be remediated.

PR.PS-02 partial match
prevents

Patching or replacing vulnerable software directly eliminates known instances of this coding weakness.

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.

A.8.29 Security testing in development and acceptance mostly match
finds

Security testing in development and acceptance can detect and prevent out-of-bounds write defects.

A.8.25 Secure development life cycle partial match
prevents

Secure development life cycle mandates practices that prevent out-of-bounds writes.

A.8.26 Application security requirements partial match
prevents

Application security requirements can specify bounds-checking and safe memory handling.

A.8.27 Secure system architecture and engineering principles partial match
prevents

Secure architecture and engineering principles reduce the likelihood of buffer overflows.

A.8.28 Secure coding partial match
prevents

Secure coding directly addresses out-of-bounds writes through language choice and coding standards.

A.8.32 Change management partial match
prevents

Change management can enforce review gates that catch unsafe memory operations before deployment.

References