CVE Intelligence
High Insecure deserialization

CVE-2020-9484 — Deserialization of Untrusted Data in Apache Software Foundation Tomcat

When using Apache Tomcat versions 10.0.0-M1 to 10.0.0-M4, 9.0.0.M1 to 9.0.34, 8.5.0 to 8.5.54 and 7.0.0 to 7.0.103 if a) an attacker is able to control the contents and name of a file on the server; and b) the server is configured to use the PersistenceManager with a FileStore; and c) the PersistenceManager is configured with sessionAttributeValueClassNameFilter="null" (the default unless a SecurityManager is used) or a sufficiently lax filter to allow the attacker provided object to be deserialized; and d) the attacker knows the relative file path from the storage location used by FileStore to the file the attacker has control over; then, using a specifically crafted request, the attacker will be able to trigger remote code execution via deserialization of the file under their control. Note that all of conditions a) to d) must be true for the attack to succeed.

Published May 20, 2020 · Updated Oct 13, 2026 · Sources: NIST National Vulnerability Database, CVE Program (cve.org) e CISA ADP · CNA: apache

Who exploits it and how urgent it is

A 0–100 score combining confirmed exploitation, ransomware and APT use, public exploits, EPSS and severity.

Detection templates (Nuclei) · 1
How the score was calculated
  • Public exploit/PoC (nuclei)+4
  • EPSS 55.5% (30-day exploitation probability)+15
  • Technical severity (high)+6

The score orders the patch queue; it does not replace your asset context (internet exposure, criticality, compensating controls).

Triage

Is it exploited, how likely is exploitation, what does it touch, and how severe do the sources call it.

Exploitation
Not confirmed
Not in CISA KEV — an absence of record, not proof it is unexploited.
EPSS FIRST
55.52%
ahead of 99% of scored CVEs · Oct 15, 2026
Affects
Apache Software Foundation
Tomcat and 25 more
CVSS base
7.0
High · 1 source(s)

CISA SSVC assessment CISA

Three decision points CISA publishes for the CVEs it assesses (SSVC 2.0.3). A stakeholder decision, not a severity score.

Exploitation
None
none · proof-of-concept · active
Automatable
No
can an attacker script the kill-chain steps
Technical impact
Total
partial · total control of the vulnerable component

Remediation

Fixes and mitigations documented by the sources — linked to the original advisory.

  • Documented patch — lists.apache.org (NIST National Vulnerability Database)
  • Documented patch — www.oracle.com (NIST National Vulnerability Database)
  • Documented patch — www.oracle.com (NIST National Vulnerability Database)
  • Documented patch — www.oracle.com (NIST National Vulnerability Database)
  • Documented patch — www.oracle.com (NIST National Vulnerability Database)
  • Documented patch — www.oracle.com (NIST National Vulnerability Database)
  • Documented patch — www.oracle.com (NIST National Vulnerability Database)
  • Documented patch — www.oracle.com (NIST National Vulnerability Database)

First 24 hours

Ordered from the record’s own fields — exposure first, because you cannot patch what you have not found. A rule-generated starting point.

  1. Identify exposed assets running the affected vendor/product/version combinations (Apache Software Foundation Tomcat, Canonical Ubuntu Linux, Debian Debian Linux…).
  2. Apply the fixed version or the patch documented under Remediation.
  3. EPSS ahead of 99% of scored CVEs: prioritize it in the patch queue.
  4. Search available logs for exploit probes matching the vulnerability class (insecure deserialization), errors and authentication anomalies.

Affected scope

Vendor, product and versions as the sources word them.

VendorProductVersionsStatusSource
Apache Software Foundation Tomcat version 9.0.0-milestone25version 9.0.0-milestone17version 9.0.0-milestone18version 9.0.0-milestone19version 9.0.0-milestone2version 9.0.0-milestone20version 9.0.0-milestone21version 9.0.0-milestone22
and 26 more version 9.0.0-milestone23version 9.0.0-milestone24version 9.0.0-milestone16version 9.0.0-milestone26version 9.0.0-milestone27version 9.0.0-milestone3version 9.0.0-milestone4version 9.0.0-milestone5version 9.0.0-milestone6version 9.0.0-milestone7version 9.0.0-milestone8version 9.0.0-milestone9≥ 7.0.0 and < 7.0.108version 10.0.0-milestone4version 10.0.0-milestone3version 10.0.0-milestone2version 10.0.0-milestone1≥ 8.5.0 and < 8.5.63≥ 9.0.1 and < 9.0.43version 9.0.0-milestone1version 9.0.0-milestone10version 9.0.0-milestone11version 9.0.0-milestone12version 9.0.0-milestone13version 9.0.0-milestone14version 9.0.0-milestone15
Vulnerable NIST National Vulnerability Database
Canonical Ubuntu Linux version 20.04version 16.04 Vulnerable NIST National Vulnerability Database
Debian Debian Linux version 10.0version 9.0version 8.0 Vulnerable NIST National Vulnerability Database
Fedoraproject Fedora version 32version 31 Vulnerable NIST National Vulnerability Database
Mcafee Epolicy Orchestrator version 5.10.0-update_3version 5.10.0-update_2version 5.10.0-update_1version 5.10.0version 5.9.1version 5.9.0 Vulnerable NIST National Vulnerability Database
Opensuse Leap version 15.1 Vulnerable NIST National Vulnerability Database
Oracle Agile Engineering Data Management version 6.2.1.0 Vulnerable NIST National Vulnerability Database
Oracle Agile Product Lifecycle Management version 9.3.5version 9.3.6version 9.3.3 Vulnerable NIST National Vulnerability Database
Oracle Communications Cloud Native Core Binding Support Function version 1.10.0 Vulnerable NIST National Vulnerability Database
Oracle Communications Cloud Native Core Policy version 1.14.0 Vulnerable NIST National Vulnerability Database
Oracle Communications Diameter Signaling Router ≥ 8.0.0.0 and ≤ 8.4.0.5 Vulnerable NIST National Vulnerability Database
Oracle Communications Element Manager ≥ 8.2.0 and ≤ 8.2.2 Vulnerable NIST National Vulnerability Database
Oracle Communications Instant Messaging Server version 10.0.1.4.0 Vulnerable NIST National Vulnerability Database
Oracle Communications Session Report Manager ≥ 8.2.0 and ≤ 8.2.2 Vulnerable NIST National Vulnerability Database
Oracle Communications Session Route Manager ≥ 8.2.0 and ≤ 8.2.2 Vulnerable NIST National Vulnerability Database
Oracle Database version 12.2.0.1version 19cversion 21c Vulnerable NIST National Vulnerability Database
Oracle Fmw Platform version 12.2.1.3.0version 12.2.1.4.0 Vulnerable NIST National Vulnerability Database
Oracle Hospitality Guest Access version 4.2.0version 4.2.1 Vulnerable NIST National Vulnerability Database
Oracle Instantis Enterprisetrack ≥ 17.1 and ≤ 17.3 Vulnerable NIST National Vulnerability Database
Oracle Managed File Transfer version 12.2.1.3.0version 12.2.1.4.0 Vulnerable NIST National Vulnerability Database
Oracle Mysql Enterprise Monitor ≤ 8.0.21 Vulnerable NIST National Vulnerability Database
Oracle Retail Order Broker version 15.0 Vulnerable NIST National Vulnerability Database
Oracle Siebel Apps - Marketing ≤ 21.9 Vulnerable NIST National Vulnerability Database
Oracle Siebel Ui Framework ≤ 20.12 Vulnerable NIST National Vulnerability Database
Oracle Transportation Management version 6.3.7 Vulnerable NIST National Vulnerability Database
Oracle Workload Manager version 19cversion 18cversion 12.2.0.1 Vulnerable NIST National Vulnerability Database

Attack characteristics

The CVSS vector, decoded. It describes the attack, not your exposure to it.

Attack vector
Local
Attack complexity
High
Privileges required
Low
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

Every base score collected

Sources score independently and may disagree; each row says who scored it and under which version.

ScoreVersionSeverityExpl.ImpactScored by
7.0 CVSS 3.1 High 1.0 5.9 nvd@nist.gov via NIST National Vulnerability Database
4.4 CVSS 2.0 Medium 3.4 6.4 nvd@nist.gov via NIST National Vulnerability Database
CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H (score shown at the top: nvd@nist.gov)

Weakness MITRE

Weakness class according to MITRE’s CWE catalog.

CWE-502 · Deserialization of Untrusted Data

Other CVEs with this weakness →

Public exploits, PoCs and detection templates

Public code that demonstrates or tests the flaw raises the odds of mass exploitation — and Nuclei templates help find vulnerable assets in your environment.

Detection templates (Nuclei)

Warning: public PoCs are sometimes disguised malware. Use them only for authorized testing in an isolated environment. This portal does not host exploit code — it only points to the sources.

EPSS over time FIRST

Oct 13, 2026 → Oct 15, 2026 · 3 reading(s) · max 55.52%

Detection

Read off the CVSS vector and the weakness class. Starting points, not tested rules.

  • Local/physical vector: focus on endpoint telemetry (EDR) from affected hosts.
  • Monitor serialized objects in requests and unexpected processes spawned by the runtime.
endpoint telemetry (EDR)application logs

Timeline

What happened to this CVE, newest first.

  • 2026
  • SSVC assessment updated
    Oct 13, 2026 · CVE Program (cve.org) e CISA ADP
  • Record published
    Oct 13, 2026
  • Fix documented
    Oct 13, 2026 · NIST National Vulnerability Database
  • CVSS changed · 7.0
    Oct 13, 2026 · NIST National Vulnerability Database
  • Source status changed · → Modified
    Oct 13, 2026 · NIST National Vulnerability Database
  • Record created in this database
    Oct 13, 2026 · NIST National Vulnerability Database
  • 2020
  • CVE published
    May 20, 2020 · apache

Source activity

Repeated readings are counted rather than listed.

  • 1× Official description updated · Oct 13, 2026 – Oct 13, 2026

References

42 on the record

Elsewhere on this site

Apache Software Foundation
every CVE for this vendor
Insecure deserialization
same class
CWE-502
other pages naming this weakness

Related CVEs (same products)

  • CVE-2026-87022 Apache Tomcat: WebSocket message smuggling with per-message-deflate 23d
  • CVE-2026-86350 Apache Tomcat: Regression in fix for CVE-2026-41293 can trigger request header mix-up 23d
  • CVE-2026-86248 Apache Tomcat: Fix for CVE-2026-34500 was incomplete. OCSP checks sometimes soft-fail with FFM even when soft-fail is disabled 23d
  • CVE-2026-79677 Apache Tomcat: WebSocket DoS due to lost asynchronous write timeout 23d
  • CVE-2026-78383 Apache Tomcat: AJP DoS via missing request body 23d
  • CVE-2026-78437 Apache Tomcat: HTTP/2 DoS via malformed request 23d

Not in any source we poll

Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.

  • No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
  • No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
  • No exploit packet captures, log samples, or incident case IDs supplied.

Answered from this record

Text assembled only from the fields above — no additional claims.

What should defenders know first?

CVE-2020-9484 is "Deserialization of Untrusted Data in Apache Software Foundation Tomcat", rated High. It affects Tomcat (Apache Software Foundation); versions are in the scope table. It is not in CISA KEV, which does not rule out exploitation. CVSS 7.0 describes technical severity. EPSS 55.52% estimates the probability of exploitation in 30 days; neither replaces your asset context. First verify whether exposed or business-critical assets run the affected versions, apply vendor fixes or mitigations, and preserve logs for review.

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