Public proof of conceptFix available

CVE-2021-40865

Q: Is CVE-2021-40865 actively exploited?

Active exploitation of CVE-2021-40865 has not been confirmed. Its EPSS score was 64.2% on 2026-10-22, the estimated probability of exploitation in the next 30 days.

Q: What is the CVSS score for CVE-2021-40865?

CVE-2021-40865 has a CVSS v3 base score of 9.8 (CRITICAL severity), with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.

A public proof of concept exists; no exploitation attested.

Published2021-10-25
Fixed in2.2.1 · 2.1.1 · 1.2.4
WeaknessCWE-502

Am I affected?

With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.

Description

An Unsafe Deserialization vulnerability exists in the worker services of the Apache Storm supervisor server allowing pre-auth Remote Code Execution (RCE). Apache Storm 2.2.x users should upgrade to version 2.2.1 or 2.3.0. Apache Storm 2.1.x users should upgrade to version 2.1.1. Apache Storm 1.x users should upgrade to version 1.2.4

Timeline

dates in UTC

2021-10-2513:15CVE publishedNVD
2026-10-2319:23First public proof of conceptPoC-in-GitHub
2026-10-2319:23EPSS crossed 10 %FIRST EPSS

Observed activity

isMalicious corpus · updated 2026-10-23 18:48 UTC

Indicators tagged with this CVE, per day0 indicators over 7 days

Block these indicators

Firewall list (EDL, text): https://api.ismalicious.com/edl/cve/CVE-2021-40865?format=txt
CSV export: https://api.ismalicious.com/edl/cve/CVE-2021-40865?format=csv
TAXII collection of exploited CVEs
The EDL and CSV take an API key on the Pro plan.

Versions per branch

NVD

Apache storm

Branch	Affected	Fixed in	Source
2.2	≥ 2.2.0, < 2.2.1	2.2.1	NVD
2.1	≥ 2.1.0, < 2.1.1	2.1.1	NVD
1.x	≥ 1.0.0, < 1.2.4	1.2.4	NVD

as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.

Fix

Update Apache storm to 2.2.1 · 2.1.1 · 1.2.4

Advisories and patches

lists.apache.orgVendor Advisory

Detection

read 2026-10-23 19:23 UTC

Nuclei template: none so far
Exploit-DB: no entry
Proof-of-concept repositories: 1 repository, unverifiedhktalent/CVE-2021-40865

Sources

NVDCVSS 3.19.8read 2026-10-23
NVDCVSS 2.07.5read 2026-10-23
CNAweakness (CWE)CWE-502read 2026-10-23
NVDweakness (CWE)CWE-502read 2026-10-23
FIRST EPSSEPSS score64.2 %read 2026-10-23
PoC-in-GitHubproof of concept1read 2026-10-23

Technical details

CVSS v3 Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Published: 2021-10-25
Last Modified: 2026-06-17
NVD status: Modified

Frequently asked questions

What is CVE-2021-40865?

Is CVE-2021-40865 actively exploited?

Active exploitation of CVE-2021-40865 has not been confirmed. Its EPSS score was 64.2% on 2026-10-22, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2021-40865?

CVE-2021-40865 has a CVSS v3 base score of 9.8 (CRITICAL severity), with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.

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