CVE-2021-25659
No exploitation reported by the sources we read.
- Published2021-08-10
- Fixed in6.0.9
- WeaknessCWE-400
Am I affected?
Debian, Ubuntu or Red Hat sometimes backport a fix without changing the upstream version number: such a version reads « to verify », never « 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
A vulnerability has been identified in Automation License Manager 5 (All versions), Automation License Manager 6 (All versions < V6.0 SP9 Update 2). Sending specially crafted packets to port 4410/tcp of an affected system could lead to extensive memory being consumed and as such could cause a denial-of-service preventing legitimate users from using the system.
Timeline
dates in UTC- 2021-08-1011:15CVE publishedNVD
Observed activity
isMalicious corpus · updated 2026-10-23 18:48 UTCBlock these indicators
- Firewall list (EDL, text): https://api.ismalicious.com/edl/cve/CVE-2021-25659?format=txt
- CSV export: https://api.ismalicious.com/edl/cve/CVE-2021-25659?format=csv
- TAXII collection of exploited CVEs
- The EDL and CSV take an API key on the Pro plan.
Versions per branch
NVD| Branch | Affected | Fixed in | Source |
|---|---|---|---|
| 6.0 | ≥ 5.0.0, < 6.0.9 | 6.0.9 | NVD |
as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.
Distribution builds and vendor advisories
Packages from OSV.dev and products from the vendors' CSAF advisories.
version not verifiedVersions not verified: read as OSV.dev and the vendors publish them, not checked against each vendor's release list.
Vendor advisories
Siemens Automation License Manager
Automation License Manager 5 · Automation License Manager 6
Fix
- Update Siemens automation license manager to 6.0.9
- Vendor fix CISA ICSA-21-222-02 · 1 productUpdate to V6.0 SP9 Update 2 or later
- Mitigation from the vendor CISA ICSA-21-222-02 · 2 productsOn the Automation License Manager settings menu disable "Allow Remote Connections"
- Mitigation from the vendor CISA ICSA-21-222-02 · 2 productsIf remote connections are needed, limit remote access to port 4410/tcp to trusted systems only
- No fix available, says the vendor CISA ICSA-21-222-02 · 1 productCurrently no remediation is available
Advisories and patches
- cert-portal.siemens.comPatch · Vendor Advisory
Detection
- Nuclei template
- none so far ProjectDiscovery
- Exploit-DB
- no entry Exploit-DB
- Proof-of-concept repositories
- none listed PoC-in-GitHub
Sources
- NVDCVSS 3.17.5read 2026-10-23
- NVDCVSS 2.05read 2026-10-23
- CNAweakness (CWE)CWE-400read 2026-10-23
- NVDweakness (CWE)CWE-400read 2026-10-23
- FIRST EPSSEPSS score1.0 %2026-10-22
Technical details
- CVSS v3 Vector
- CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- Published
- 2021-08-10
- Last Modified
- 2026-06-17
- NVD status
- Modified
Frequently asked questions
What is CVE-2021-25659?
Is CVE-2021-25659 actively exploited?
What is the CVSS score for CVE-2021-25659?
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Surveillance reads the versions in your stack — a domain, a lockfile or a list — checks each CVE against the ranges its sources publish, and alerts you when one you run is exploited or enters CISA KEV. A version it cannot read stays « version not verified ».
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Related vulnerabilities
Same product first, then the same vendor advisory and the same publication week.