Background exploitation KEV catalog No authentication

CVE-2023-36844

Juniper Junos OS EX Series PHP External Variable Modification Vulnerability

CheckOps priority index

7.2/10 Patch within 7 days

Severity5.3

Probability9.0

Exploitation4/5

Severity = CVSS. Probability = EPSS (FIRST). Exploitation = public signals: KEV, EUVD, ransomware, EPSS above 10 %, no account required.

EPSS · today 90.0% higher than 99.8% of CVEs

CVSS 3.1 5.3 AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:

Exploited for 1,086 days 13 Nov 2023

CISA due date 17 Nov 2023 for US federal agencies

Exploitation probability EPSS · FIRST

EPSS probability (%)Percentile among all CVEs

Exploitation signals 4 / 5

KEV catalog (CISA)13 Nov 2023
Exploited in EUVD (ENISA)13 Nov 2023
Used by ransomwareno
EPSS above 10 %90.0%
No account, over the networkyes

What to do

Fix

Apply the vendor’s fix as soon as it is available.

CISA guidance: Apply mitigations per vendor instructions or discontinue use of the product if mitigations are unavailable.

Meanwhile

Take the service off the internet or restrict access to it, watch the logs and look for signs of compromise.

Manufacturers (CRA)

Exploited vulnerability in your product: early warning to ENISA within 24 h, then notification within 72 h (Article 14 of the Cyber Resilience Act). The CRA explained

Description ENISA EUVD

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.

Affected products

Junos OS

Affected versions

21.1 <21.1*
22.4 <22.4R2-S2, 22.4R3
21.3 <21.3R3-S5
23.2 <23.2R1-S1, 23.2R2
0 <20.4R3-S9
22.1 <22.1R3-S4
21.4 <21.4R3-S5
22.2 <22.2R3-S2
22.3 <22.3R3-S1
21.2 <21.2R3-S6

Weaknesses (CWE)

CWE-473

Open source packages OSV

Affected libraries according to OSV, with fixed versions.

Timeline

17 Aug 2023
Published
13 Nov 2023
Exploitation reported (ENISA)
13 Nov 2023
Added to the KEV catalog
17 Nov 2023
CISA remediation due date
26 Sept 2026
EPSS peak: 90.0%

References

Other exploited vulnerabilities from the same vendor

CVE-2015-7755Juniper ScreenOS Improper Authentication Vulnerability
8.2 · Background exploitation
CVE-2025-21590Juniper Junos OS Improper Isolation or Compartmentalization Vulnerability
3.9 · Background exploitation
CVE-2023-36851Juniper Junos OS SRX Series Missing Authentication for Critical Function Vulnerability
4.0 · Background exploitation
CVE-2023-36847Juniper Junos OS EX Series Missing Authentication for Critical Function Vulnerability
7.0 · Background exploitation
CVE-2023-36846Juniper Junos OS SRX Series Missing Authentication for Critical Function Vulnerability
7.3 · Background exploitation
CVE-2023-36845Juniper Junos OS EX Series and SRX Series PHP External Variable Modification Vulnerability
9.2 · Background exploitation