Medium File handling

CVE-2021-24122 — Apache Tomcat information disclosure

When serving resources from a network location using the NTFS file system, Apache Tomcat versions 10.0.0-M1 to 10.0.0-M9, 9.0.0.M1 to 9.0.39, 8.5.0 to 8.5.59 and 7.0.0 to 7.0.106 were susceptible to JSP source code disclosure in some configurations. The root cause was the unexpected behaviour of the JRE API File.getCanonicalPath() which in turn was caused by the inconsistent behaviour of the Windows API (FindFirstFileW) in some circumstances.

Published Jan 14, 2021 · Updated Oct 13, 2026 · Sources: NIST National Vulnerability Database, CVE Program (cve.org) e CISA ADP · CNA: apache

Low

Who exploits it and how urgent it is

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

No exploitation signal in the sources consulted so far.

How the score was calculated

EPSS 22.9% (30-day exploitation probability)+15
Technical severity (medium)+3
Automatable exploitation (SSVC)+3

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

22.85%

ahead of 98% of scored CVEs · Oct 15, 2026

Affects

Apache Software Foundation

Tomcat and 2 more

CVSS base

5.9

Medium · 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

Yes

can an attacker script the kill-chain steps

Technical impact

Partial

partial · total control of the vulnerable component

Remediation

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

No fix documented by the sources we poll. That does not mean none exists: check the vendor advisory.

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.

Identify exposed assets running the affected vendor/product/version combinations (Apache Software Foundation Tomcat, Debian Debian Linux, Oracle Agile Product Lifecycle Management).
The attack is network-based and needs no privileges: restrict exposure (ACLs, VPN, WAF) until patched.
No fix documented in the sources: reduce exposure and monitor the vendor advisory.
EPSS ahead of 98% of scored CVEs: prioritize it in the patch queue.
Search available logs for exploit probes matching the vulnerability class (file handling), errors and authentication anomalies.

Affected scope

Vendor, product and versions as the sources word them.

Vendor	Product	Versions	Status	Source
Apache Software Foundation	Tomcat	version 10.0.0-milestone3version 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-milestone7 and 31 more version 9.0.0-milestone8version 9.0.0-milestone9version 10.0.0-milestone1version 10.0.0-milestone2version 9.0.0-milestone25version 10.0.0-milestone4version 10.0.0-milestone5version 10.0.0-milestone6version 10.0.0-milestone7version 10.0.0-milestone8version 10.0.0-milestone9version 9.0.0-milestone24≥ 7.0.0 and ≤ 7.0.106≥ 8.5.0 and ≤ 8.5.59≥ 9.0.1 and ≤ 9.0.39version 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-milestone15version 9.0.0-milestone16version 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-milestone22version 9.0.0-milestone23	Vulnerable	NIST National Vulnerability Database
Apache Software Foundation	Tomcat	≥ Apache Tomcat 10 and < 10.0.0-M10≥ Apache Tomcat 9 and < 9.0.40≥ Apache Tomcat 8.5 and < 8.5.60≥ Apache Tomcat 7 and < 7.0.106	Vulnerable	CVE Program (cve.org) e CISA ADP
Debian	Debian Linux	version 9.0	Vulnerable	NIST National Vulnerability Database
Oracle	Agile Product Lifecycle Management	version 9.3.6version 9.3.3	Vulnerable	NIST National Vulnerability Database

Attack characteristics

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

Attack vector

Network

Attack complexity

High

Privileges required

None

User interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

None

Availability

None

Every base score collected

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

Score	Version	Severity	Expl.	Impact	Scored by
5.9	CVSS 3.1	Medium	2.2	3.6	nvd@nist.gov via NIST National Vulnerability Database
4.3	CVSS 2.0	Medium	8.6	2.9	nvd@nist.gov via NIST National Vulnerability Database

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N (score shown at the top: nvd@nist.gov)

Weakness MITRE

Weakness class according to MITRE’s CWE catalog.

CWE-706 · Use of Incorrectly-Resolved Name or Reference

Other CVEs with this weakness →

EPSS over time FIRST

Oct 13, 2026 → Oct 15, 2026 · 3 reading(s) · max 22.85%

Detection

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

Prioritize edge telemetry for the network-reachable component (proxy, WAF, IDS/IPS).
Monitor file creation in web directories and paths with traversal sequences (../).

web/proxy/WAF logsnetwork IDS/IPSfile integrity (FIM)endpoint telemetry (EDR)

Timeline

What happened to this CVE, newest first.

2026
Affected products added · apache software foundation/apache tomcat
Oct 13, 2026 · CVE Program (cve.org) e CISA ADP
SSVC assessment updated
Oct 13, 2026 · CVE Program (cve.org) e CISA ADP
Record published
Oct 13, 2026
CVSS changed · 5.9
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
2021
CVE published
Jan 14, 2021 · apache

Source activity

Repeated readings are counted rather than listed.

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

References

11 on the record

lists.apache.org/thread.html/r1595889b083e05986f42b944dc43060d6b083022260b6ea64d2cec52
Mailing List, Vendor Advisory, x_refsource_MISC, mailing-list, x_refsource_MLIST, NIST National Vulnerability Database
www.oracle.com//security-alerts/cpujul2021.html
Third Party Advisory, x_refsource_MISC, NIST National Vulnerability Database
www.openwall.com/lists/oss-security/2021/01/14/1
Mailing List, Third Party Advisory, mailing-list, x_refsource_MLIST, NIST National Vulnerability Database
lists.apache.org/thread.html/r1595889b083e05986f42b944dc43060d6b083022260b6ea64d2cec52
mailing-list, x_refsource_MLIST, NIST National Vulnerability Database
lists.apache.org/thread.html/rb32a73b7cb919d4f44a2596b6b951274c0004fc8b0e393d6829a45f9
mailing-list, x_refsource_MLIST, NIST National Vulnerability Database
lists.apache.org/thread.html/r7e0bb9ea415724550e2b325e143b23e269579e54d66fcd7754bd0c20
mailing-list, x_refsource_MLIST, NIST National Vulnerability Database
lists.apache.org/thread.html/rca833c6d42b7b9ce1563488c0929f29fcc95947d86e5e740258c8937
mailing-list, x_refsource_MLIST, NIST National Vulnerability Database
lists.debian.org/debian-lts-announce/2021/03/msg00018.html
Mailing List, Third Party Advisory, mailing-list, x_refsource_MLIST, NIST National Vulnerability Database
security.netapp.com/advisory/ntap-20210212-0008/
Third Party Advisory, x_refsource_CONFIRM, NIST National Vulnerability Database
lists.apache.org/thread.html/r776c64337495bf28b7d5597268114a888e3fad6045c40a0da0c66d4d
mailing-list, x_refsource_MLIST, NIST National Vulnerability Database
lists.apache.org/thread.html/r7382e1e35b9bc7c8f320b90ad77e74c13172d08034e20c18000fe710
mailing-list, x_refsource_MLIST, NIST National Vulnerability Database

Elsewhere on this site

Apache Software Foundation
every CVE for this vendor

File handling
same class

CWE-706
other pages naming this weakness

Related CVEs (same products)

High CVE-2026-87022 Apache Tomcat: WebSocket message smuggling with per-message-deflate 22d
Critical CVE-2026-86350 Apache Tomcat: Regression in fix for CVE-2026-41293 can trigger request header mix-up 22d
Critical 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 22d
High CVE-2026-78437 Apache Tomcat: HTTP/2 DoS via malformed request 22d
High CVE-2026-78383 Apache Tomcat: AJP DoS via missing request body 22d
High CVE-2026-79677 Apache Tomcat: WebSocket DoS due to lost asynchronous write timeout 22d

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 fixed version, patch or mitigation documented.
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-2021-24122 is "Apache Tomcat information disclosure", rated Medium. 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 5.9 describes technical severity. EPSS 22.85% 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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