`CVE-2020-4450` IBM WebSphere Application Server

Affected software	IBM WebSphere Application Server
Severity	9.8 Critical CVSS 3.1 3 scores
Weakness	Deserialization of untrusted data (CWE-502)
Published	5 Jun 2020
Updated	17 Oct 2026

Description

IBM WebSphere Application Server 8.5 and 9.0 traditional could allow a remote attacker to execute arbitrary code on the system with a specially-crafted sequence of serialized objects. IBM X-Force ID: 181231.

Exploitation status

Exploited

Real-world exploitation reported by VulnCheck KEV. CISA has not confirmed it.

CISA KEV not listed
VulnCheck KEV listed Exploitation reported in the wild. 1 citation · 1 exploit · earliest 2024-09-18.
CISA Vulnrichment no assessment published
Indexed PoC none indexed
EPSS 35% chance in 30 days A model's forecast, not a report of exploitation. Higher than 98% of all scored CVEs.

VulnCheck KEV

Exploitation evidence from VulnCheck Known Exploited Vulnerabilities (VulnCheck KEV), used under VulnCheck's community terms. View CVE-2020-4450 in VulnCheck (free account).

Evidence	Source	Detail	Date
Reported exploitation	media.defense.gov	/2024/Sep/18/2003547016/-1/-1/0/CSA-PRC-LINKED-ACTORS-BOTNET.PDF	2024-09-18
Exploit reference	VulnCheck XDB 5a744e3a8a55	Exploit type: initial-access	2022-05-18

Evidence

Source

Detail

Date

Reported exploitation

media.defense.gov

/2024/Sep/18/2003547016/-1/-1/0/CSA-PRC-LINKED-ACTORS-BOTNET.PDF

2024-09-18

Exploit reference

VulnCheck XDB 5a744e3a8a55

Exploit type: initial-access

2022-05-18

Waratek protection

Protected by Waratek

Waratek has a rule that blocks attacks on this vulnerability.

Protection full Deserialization, Process
Action available security rule
Review human Researcher
Record active

Decided by	A researcher's recorded decision for this specific CVE
Finding	A researcher found this CVE protected by the Marshal RCE rule, ARMR Process rule.

Decided by

A researcher's recorded decision for this specific CVE

Finding

A researcher found this CVE protected by the Marshal RCE rule, ARMR Process rule.

Waratek research note

written 2026-11-13

Written by a Waratek engineer who reviewed this CVE. Their decision sets the status above, ahead of every automated rule except a withdrawal.

Comments

Rule Name: Marshal RCE rule, ARMR Process rule

Native-deserialization RCE over IIOP (WSIFPort_EJB gadget through JNDI/WSIF to ELProcessor.eval); Marshal deserialize(java)+rce() intercepts the readObject chain and the Process rule blocks the payload's bash exec (with /bin/* and /usr/* listed). A payload that acts inside the running application without starting a program gets past the Process rule.

How to mitigate CVE-2020-4450

Apply the vendor's fix for IBM WebSphere Application Server. Until you can, Waratek RASP blocks exploitation with its deserialization and process rules. It runs inside the Java application, with no code changes.

Waratek RASP Runtime protection for Java applications

CVSS

9.8 CRITICAL v3.1 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H 3 metrics

We show the highest score from the newest CVSS version. Scores from different versions can't be compared, and the first score listed is sometimes a 0.0 placeholder.

Version Score Band Vector Assigner Type

CVSS 3.1 9.8 CRITICAL CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H NVD Primary published

CVSS 3.0 9.8 CRITICAL CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H psirt@us.ibm.com Secondary

CVSS 2.0 10.0 none AV:N/AC:L/Au:N/C:C/I:C/A:C NVD Primary

Version	Score	Band	Vector	Assigner	Type
CVSS 3.1	9.8	CRITICAL	`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H`	NVD	Primary	published
CVSS 3.0	9.8	CRITICAL	`CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H`	psirt@us.ibm.com	Secondary
CVSS 2.0	10.0	none	`AV:N/AC:L/Au:N/C:C/I:C/A:C`	NVD	Primary

Affected software and releases

Products and versions

1 product, 2 version entries

Source	Vendor	Product	Scheme	Affected versions
nvd	ibm	websphere application server	generic	≥ 8.5.0.0 and ＜ 8.5.5.18 · ≥ 9.0.0.0 and ＜ 9.0.5.5

Source

Vendor

Product

Scheme

Affected versions

nvd

ibm

websphere application server

generic

≥ 8.5.0.0 and ＜ 8.5.5.18 · ≥ 9.0.0.0 and ＜ 9.0.5.5

References

URL	Tags
https://exchange.xforce.ibmcloud.com/vulnerabilities/181231	VDB Entry, Vendor Advisory
https://www.ibm.com/support/pages/node/6220294	Patch, Vendor Advisory
https://www.zerodayinitiative.com/advisories/ZDI-20-689/	Third Party Advisory, VDB Entry

URL

Timeline

Published	2020-06-05	By the CVE Program.
VulnCheck KEV: earliest evidence	2024-09-18	Date of the oldest evidence of exploitation in VulnCheck KEV's record. VulnCheck does not publish the date it listed the CVE.
NVD record modified	2026-06-17	NVD's own last-modified date for this record.
Last VRT activity	2026-10-17	Most recent commit touching this CVE's classification, patch or rule file.
Classification created	2026-11-13	First commit adding this CVE's research note.

Published

2020-06-05

By the CVE Program.

VulnCheck KEV: earliest evidence

2024-09-18

Date of the oldest evidence of exploitation in VulnCheck KEV's record. VulnCheck does not publish the date it listed the CVE.

NVD record modified

2026-06-17

NVD's own last-modified date for this record.

Last VRT activity

2026-10-17

Most recent commit touching this CVE's classification, patch or rule file.

Classification created

2026-11-13

First commit adding this CVE's research note.

How VRT decided (4 of 24 rules ran)

4 of 24 rules ran. The rest didn't run because an earlier rule had already settled the CVE.

# Rule Outcome Status Detail

identity: Does this identifier describe a vulnerability at all? the first rule that matches decides

1 rejected no match CVE Program withdrawal of this identifier

scope: Is it a vulnerability Waratek protects? the first rule that matches decides

2 armr-patch-file no match An ARMR patch file on disk for this CVE

3 armr-secure-rule-file no match An ARMR security-rule template on disk for this CVE

4 manual-classification decided it matched Protected by Waratek A researcher found this CVE protected by the Marshal RCE rule, ARMR Process rule.

5 manual classification not reached Manual classification of this CVE in the legacy dataset

6 non-java-upstream not reached A root cause in non-Java code: an OS kernel, a C library, or a bundled runtime

7 oracle-component not reached The defect being in a component of a tracked product the agent does not reach: JavaFX, the Java SE installer, the JInitiator browser plug-in, the native WebLogic proxy plug-in, or a native part of Oracle Application Server or Collaboration Suite (HTTP Server, Web Cache, Internet Directory, mail and calendar servers). Oracle gives these no CPE of their own and names them only in the description.

8 java-client-side not reached Oracle's own risk-matrix note saying the CVE is reached only through untrusted code in the Java sandbox (applets, Web Start) or only through a client installation of Java, so a server running its own trusted code is not exposed

9 osv-maven not reached An OSV.dev record of this CVE affecting a package published to Maven Central. When every such package is one business applications do not use (Minecraft mods and launchers, Fastjson) and no tracked product is named by CPE, it settles the CVE as Outside Waratek scope instead

10 cna-maven-package not reached An affected Maven artifact named by the CNA itself

11 known-cpe-product not reached An NVD CPE naming a product ARMR tracks

12 cna-cpe-product not reached A CPE the CNA published naming a tracked product. Oracle publishes these on advisory day, months before NVD.

13 oracle-advisory-family not reached A tracked product family named in Oracle's own risk matrix. CPE cannot carry a suite name, only a module.

14 cna-named-product not reached A tracked product named in words by the CVE's own CNA, on a record with no CPE yet. Apache and Eclipse publish these on advisory day, before NVD adds CPE data.

15 non-deployable-product not reached The only affected product being a sealed appliance image, where Java runs but no -javaagent can be attached

16 unmatched-product not reached No tracked product matched above, and none present at all

disposition: What do we do about one that is? every rule runs

17 patch-hint not reached A reference pointing at the upstream fix: a commit, a PR, a Red Hat bug

18 open-source-maven not reached The affected package being open source on Maven, so the fix can be read

19 poc-derivable not reached An indexed exploit clearing the evidence bar to reverse-engineer, where there is no source to read

20 no-exploit not reached Nothing to build a rule from yet: no published exploit, no CISA record of exploitation and no source-level change to read

21 secure-rule-match not reached A vulnerability class already blocked by an ARMR security rule

22 exploited-no-fix-or-poc not reached Somebody exploiting this CVE (a CISA or VulnCheck KEV listing, or a CISA verdict of active exploitation), with no fix, source code or PoC to build a rule from

23 below-action-threshold not reached Medium or Low severity, no CISA or VulnCheck KEV listing, no PoC clearing the evidence bar, no CISA verdict, no Oracle advisory

24 no-exploit-published not reached Exploit code for this candidate, published in a reviewed catalogue or a GitHub repository with 5 or more stars, or in use per CISA or VulnCheck; not only a CISA verdict, a forecast, or nothing at all

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