7.5

CVE-2021-42340: DoS via memory leak with WebSocket connections

Modified
AliasesRHBA-2022:8077UBUNTU-CVE-2021-42340DEBIAN-CVE-2021-42340
Published 14-10-2021Last modified 04-08-2024

Vulnerability summary

CVE-2021-42340 is a high (CVSS 7.5) vulnerability in apache software foundation apache tomcat. EPSS estimates a 11.80% chance of exploitation in the next 30 days, higher than 96% of scored vulnerabilities.

Priority
Prioritisesevere

Severe, CVSS 7.5 (NVD); no exploitation reported by the 5 checked sources; EPSS 12% (FIRST, 03-11-2026)

Source freshness unavailable

How is this decided?
CVSS score
7.5/10
010
High · v3.1 (NVD)
EPSS score
11.80%
0%100%
Medium · 0.00 pp in 30 days
KEVNot listedNot listed by any tracked catalog.
RansomwareNot flaggedNo ransomware use recorded.
Public exploits0No public exploits recorded

Advisory lineage

Upstream 0 · Downstream 2
MGASA-2021-0485RHSA-2021:4861

Timeline

  1. 14-10-2021
    PublishedVulnerability first disclosed.
  2. 04-08-2024
    Last modifiedVulnerability information updated.

Description

The fix for bug 63362 present in Apache Tomcat 10.1.0-M1 to 10.1.0-M5, 10.0.0-M1 to 10.0.11, 9.0.40 to 9.0.53 and 8.5.60 to 8.5.71 introduced a memory leak. The object introduced to collect metrics for HTTP upgrade connections was not released for WebSocket connections once the connection was closed. This created a memory leak that, over time, could lead to a denial of service via an OutOfMemoryError.

CVSS metrics

6 scores · 5 sources · 2 versions

EPSS trend

Probability

11.80%

Chance of exploitation in the next 30 days

Percentile

96%

Versus all other CVEs

30-day change

No change 0.00 pp

From 11.80% on 04-10-2026

04-10-202603-11-2026

Known exploited

Compare KEV catalogs
CISA KEV

Not in the CISA KEV catalog.

ENISA CNW

Not in the ENISA CNW catalog.

CIRCL

Not in the CIRCL catalog.

Public exploits

0 found

No public exploits indexed.

Weaknesses

CWE · root cause

Affected systems

Version check

Known conditions: network-reachable, no authentication, no user interaction (CVSS vector). Other conditions: not stated in public data.

Oracle13 products
Debian2 products
Netapp2 products
Redhat2 products
  • pki-servlet-4.0-api< 1:9.0.50-1.el9
  • pki-servlet-engine< 1:9.0.50-1.el9
Ubuntu2 products
  • tomcat8All versions (No fix recorded)
  • tomcat9All versions (No fix recorded)
Apache1 product
  • tomcatEOL≥ 8.5.60, < 8.5.72 | ≥ 9.0.40, < 9.0.54 | ≥ 10.0.1, < 10.0.12 | 10.0.0:milestone10 | 10.1.0:milestone1 | 10.1.0:milestone2 | 10.1.0:milestone3 | 10.1.0:milestone4 | 10.1.0:milestone5
Apache software foundation1 product
  • apache tomcatApache Tomcat 10 10.0.0-M10 to 10.0.11 | Apache Tomcat 10 10.1.0-M1 to 10.1.0-M5 | Apache Tomcat 9 9.0.40 to 9.0.53 | Apache Tomcat 8 8.5.60 to 8.5.71
Org.apache.tomcat1 product
  • tomcat≥ 10.1.0-M1, < 10.1.0-M6 | ≥ 10.0.0-M1, < 10.0.12 | ≥ 9.0.40, < 9.0.54 | ≥ 8.5.60, < 8.5.72

8 vendors · 24 products

References

34 links
Show all 34 references