Cyber Resilience

CVE-2023-36844

Juniper Junos ≤ 20.4

CISA KEVActive ExploitationEUVD ExploitedPublic PoC
Published
17 August 2023
Modified
24 October 2025
KEV Added
13 November 2023
Patch / advisory
View advisory
CVSS Score v3.1 5.3
Click a component to see what it means
Raw vectorCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
EPSS Score 0.91 99.8th percentile
Risk Priority 75 floored blend · peak EPSS

Summary

CVE-2023-36844 is a medium-severity PHP External Variable Modification (CWE-473) vulnerability in Juniper Junos. Its CVSS base score is 5.3 (Medium).

Operationally, exploitation aligns with the MITRE ATT&CK technique Exploit Public-Facing Application (T1190); ranked in the top 0.2% of CVEs by exploit likelihood; CISA has added it to the Known Exploited Vulnerabilities catalog; a public proof-of-concept is referenced.

Deeper analysis AI-assisted summary

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

CVE-2023-36844 is a PHP External Variable Modification vulnerability in the J-Web interface of Juniper Networks Junos OS on EX Series switches. It enables an unauthenticated network attacker to control selected PHP environment variables through a crafted request, resulting in partial loss of integrity that may facilitate chaining with other issues. The flaw affects all versions prior to 20.4R3-S9 as well as multiple later trains up to 23.2R2, including 21.1R1 and subsequent releases before the listed fixed releases in each branch.

An unauthenticated attacker with network access can submit specially formed requests to alter important environment variables. This grants limited integrity impact without requiring credentials or user interaction, potentially serving as a stepping stone to further exploitation depending on the surrounding environment.

Juniper's advisory JSA72300 details the affected releases and corresponding fixes, while CISA has added the CVE to its Known Exploited Vulnerabilities catalog. Operators should upgrade to one of the fixed versions such as 20.4R3-S9, 21.2R3-S7, 21.3R3-S5, 21.4R3-S5, 22.1R3-S4, 22.2R3-S2, 22.3R3-S1, 22.4R3, or 23.2R2 and later.

Public exploit code referencing remote code execution on EX Series devices has been posted to Packet Storm, and the vulnerability maintains a high EPSS score near 0.94.

EU & UK References

Vulnerability Data

A PHP External Variable Modification vulnerability in J-Web of Juniper Networks Junos OS on EX Series allows an unauthenticated, network-based attacker to control certain, important environment variables. Using a crafted request an attacker is able to modify certain PHP environment…

more

variables leading to partial loss of integrity, which may allow chaining to other vulnerabilities. This issue affects Juniper Networks Junos OS on EX Series: * All versions prior to 20.4R3-S9; * 21.1 versions 21.1R1 and later; * 21.2 versions prior to 21.2R3-S7; * 21.3 versions prior to 21.3R3-S5; * 21.4 versions prior to 21.4R3-S5; * 22.1 versions prior to 22.1R3-S4; * 22.2 versions prior to 22.2R3-S2; * 22.3 versions prior to 22.3R3-S1; * 22.4 versions prior to 22.4R2-S2, 22.4R3; * 23.2 versions prior to 23.2R1-S1, 23.2R2.

CWE(s)
CWE-473NVD-CWE-Other
KEV Date Added
13 November 2023

Related Threats

MITRE ATT&CK Enterprise Techniques

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 →
Derived from this CVE’s CWE(s) via the direct CWE→ATT&CK cross-walk.

CVEs Like This One

CVE-2023-36847Same product: Juniper Ex2200both on KEV
CVE-2023-36845Same product: Juniper Junosboth on KEV
CVE-2023-36851Same product: Juniper Ex2200both on KEV
CVE-2023-36846Same product: Juniper Junosboth on KEV
CVE-2024-21620Same product: Juniper Ex2200
CVE-2024-21619Same product: Juniper Ex2200
CVE-2020-1631Same product: Juniper Junosboth on KEV
CVE-2024-39565Same product: Juniper Ex2300
CVE-2015-7755Same vendor: Juniperboth on KEV
CVE-2024-21595Same product: Juniper Ex4400

Affected Assets

juniper
junos
20.4, 21.1, 21.2, 21.3, 21.4 · ≤ 20.4

Mitigating Controls

Control response

Prevent
Stop it (NIST 800-53)

—

Detect
Catch it (NIST detect / respond)

—

Harden
Shrink the surface (DISA STIG)

—

Validate
Prove the fix (OWASP ASVS)
  • V1.2.4
  • V15.3.5
  • V15.3.7

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 full match
prevents

Secure SDLC practices include input validation and safe variable handling that prevent this exact weakness.

PR.PS-01 mostly match
prevents

Secure PHP configuration (e.g., register_globals=off) directly blocks external variable injection.

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 can detect variable-injection flaws but does not itself implement the preventive controls.

A.8.25 Secure development life cycle partial match
prevents

Secure development lifecycle mandates input validation and variable handling rules that directly prevent external variable tampering.

A.8.26 Application security requirements partial match
prevents

Application security requirements explicitly call for protection against tainted input sources such as query parameters and cookies.

A.8.28 Secure coding partial match
prevents

Secure coding standards require disabling register_globals and sanitizing all external inputs, eliminating the root cause of CWE-473.

A.8.3 Information access restriction none match
none

Information access restriction limits what data users can reach, indirectly reducing impact of tampered variables.

References