No exploitation reportedFix available

CVE-2021-25668

Q: Is CVE-2021-25668 actively exploited?

Active exploitation of CVE-2021-25668 has not been confirmed. Its EPSS score was 1.6% on 2026-10-22, the estimated probability of exploitation in the next 30 days.

Q: What is the CVSS score for CVE-2021-25668?

CVE-2021-25668 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.

No exploitation reported by the sources we read.

Published2021-04-22
Fixed in5.5.1
WeaknessCWE-122 · CWE-787

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

A vulnerability has been identified in SCALANCE X200-4P IRT (All versions < 5.5.1), SCALANCE X201-3P IRT (All versions < 5.5.1), SCALANCE X201-3P IRT PRO (All versions < 5.5.1), SCALANCE X202-2 IRT (All versions < 5.5.1), SCALANCE X202-2P IRT (incl. SIPLUS NET variant) (All versions < 5.5.1), SCALANCE X202-2P IRT PRO (All versions < 5.5.1), SCALANCE X204 IRT (All versions < 5.5.1), SCALANCE X204 IRT PRO (All versions < 5.5.1), SCALANCE X204-2 (incl. SIPLUS NET variant) (All versions < V5.2.5), SCALANCE X204-2FM (All versions < V5.2.5), SCALANCE X204-2LD (incl. SIPLUS NET variant) (All versions < V5.2.5), SCALANCE X204-2LD TS (All versions < V5.2.5), SCALANCE X204-2TS (All versions < V5.2.5), SCALANCE X206-1 (All versions < V5.2.5), SCALANCE X206-1LD (All versions < V5.2.5), SCALANCE X208 (incl. SIPLUS NET variant) (All versions < V5.2.5), SCALANCE X208PRO (All versions < V5.2.5), SCALANCE X212-2 (incl. SIPLUS NET variant) (All versions < V5.2.5), SCALANCE X212-2LD (All versions < V5.2.5), SCALANCE X216 (All versions < V5.2.5), SCALANCE X224 (All versions < V5.2.5), SCALANCE XF201-3P IRT (All versions < 5.5.1), SCALANCE XF202-2P IRT (All versions < 5.5.1), SCALANCE XF204 (All versions < V5.2.5), SCALANCE XF204 IRT (All versions < 5.5.1), SCALANCE XF204-2 (incl. SIPLUS NET variant) (All versions < V5.2.5), SCALANCE XF204-2BA IRT (All versions < 5.5.1), SCALANCE XF206-1 (All versions < V5.2.5), SCALANCE XF208 (All versions < V5.2.5). Incorrect processing of POST requests in the webserver may result in write out of bounds in heap. An attacker might leverage this to cause denial-of-service on the device and potentially remotely execute code.

Timeline

dates in UTC

2021-04-2221:15CVE publishedNVD

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-2021-25668?format=txt
CSV export: https://api.ismalicious.com/edl/cve/CVE-2021-25668?format=csv
TAXII collection of exploited CVEs
The EDL and CSV take an API key on the Pro plan.

Versions per branch

NVD

Siemens scalance x200-4p irt firmwareversion to verify

Branch	Affected	Fixed in	Source
5.5	< 5.5.1	5.5.1	NVD

Siemens scalance x201-3p irt firmwareversion to verify

Branch	Affected	Fixed in	Source
5.5	< 5.5.1	5.5.1	NVD

Siemens scalance x201-3p irt pro firmwareversion to verify

Branch	Affected	Fixed in	Source
5.5	< 5.5.1	5.5.1	NVD

26 more products in the sources.

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

ICSA-21-103-07 CISA29 known affected
Siemens Web Server of SCALANCE X200 (Update A)
SCALANCE X200-4P IRT · SCALANCE X201-3P IRT · SCALANCE X201-3P IRT PRO · +26 more

Full record on NVD

Fix

Update Siemens scalance x200-4p irt firmware to 5.5.1
Vendor fix CISA ICSA-21-103-07 · 12 productsUpdate to V5.5.1 or later version
Vendor fix CISA ICSA-21-103-07 · 17 productsUpdate to V5.2.5 or later version
Mitigation from the vendor CISA ICSA-21-103-07 · 29 productsLimit network traffic of web servers of SCALANCE X switches to trusted connections by firewall rules (port 443/tcp and 80/tcp).

Advisories and patches

cert-portal.siemens.comPatch · Vendor Advisory

Detection

Nuclei template: none so far
Exploit-DB: no entry
Proof-of-concept repositories: none listed

Sources

NVDCVSS 3.19.8read 2026-10-23
NVDCVSS 2.07.5read 2026-10-23
CNAweakness (CWE)CWE-122read 2026-10-23
NVDweakness (CWE)CWE-787read 2026-10-23
FIRST EPSSEPSS score1.6 %2026-10-22

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: 2021-04-22
Last Modified: 2026-06-17
NVD status: Modified

Frequently asked questions

What is CVE-2021-25668?

Is CVE-2021-25668 actively exploited?

Active exploitation of CVE-2021-25668 has not been confirmed. Its EPSS score was 1.6% on 2026-10-22, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2021-25668?

CVE-2021-25668 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.

Running SCALANCE X200-4P IRT (All? Hear about its next vulnerability

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 ».

Get alerts for this product CISA KEV additions, October 2026 Search CVEs

No credit card required · No monthly cap on website lookups · 250 API requests/month

Go further

Following what attackers exploit right now? The CISA KEV additions of the month, with their patch deadlines.
Running this software? Vulnerability monitoring alerts you to new vulnerabilities in your products.

Related vulnerabilities

Same product first, then the same vendor advisory and the same publication week.

Back to CVE Database