CVE-2021-21826

highpriority · track · 39EPSS 0.011 · 66 %ileEURUUS

grimoire priorityP2 · Scheduled

Exploitable?

—

no known exploitation

Likely / severe?

1.14% (66th) EPSS

CVSS 7.5 · high

Is it mine?

12 products

Check your exposure

Who says so?

5 sources

cnnvd · enisa_euvd · fstec_bdu · cisa_csaf_ot

EPSS · scored 2026-10-27

A heap-based buffer overflow vulnerability exists in the XML Decompression DecodeTreeBlock functionality of AT&T Labs Xmill 0.7. Within `DecodeTreeBlock` which is called during the decompression of an XMI file, a UINT32 is loaded from the file and used as trusted input as the length of a buffer. An attacker can provide a malicious file to trigger this vulnerability.

remediations

Vendor fix, mitigation, or workaround guidance, as published by each source.

No vendor fix yet; a mitigation is available.

MitigationEcoStruxure Control Expertcisa_csaf_ot
AT&T Labs have stated this software is longer supported and recommends vendors to move away from using it.
MitigationEcoStruxure Process Expertcisa_csaf_ot
AT&T Labs have stated this software is longer supported and recommends vendors to move away from using it.
MitigationSCADAPack RemoteConnect for x70cisa_csaf_ot
AT&T Labs have stated this software is longer supported and recommends vendors to move away from using it.

cvss

Technical severity, 0–10. One row per scoring source.

9.8

010

base score 0–10 · higher = more severe · hover a vector to decode⚠ sources disagree · high–critical · 7.5–9.8

v2.07.5highAV:N/AC:L/Au:N/C:P/I:P/A:Pprimary · NVD / NIST USexploitability 10 · impact 6.4

v3.19.8criticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:Hprimary · NVD / NIST USexploitability 3.9 · impact 5.9

v3.08.1highCVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:Hsecondary · talos-cna@cisco.com USexploitability 2.2 · impact 5.9

v3.08.1highCVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:Hsecondary · CISA US

v3.08.1highCVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:Hsecondary · ENISA EU

v3.18.1highAV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:Hsecondary · FSTEC (BDU) RU

v3.19criticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H/E:Usecondary · CVSS-BT (t0sche)

weaknesses

The CWE weakness classes this flaw belongs to.

CWE-787USprimaryCWE-120USCWE-120USCWE-120USCWE-787US

affected products (12)

Products and version ranges known to be affected.

EcoStruxure Control Expert: All versions (including former Unity Pro) prior to V15.1 HF001all versionscisa_csaf_otUS
EcoStruxure Process Expert: All versions (including former HDCS) prior to V2021all versionscisa_csaf_otUS
SCADAPack RemoteConnect for x70: All versions prior to R2.7.3all versionscisa_csaf_otUS
Schneider Electric Software, LLC EcoStruxure Control Expert< 15.1 HF001 (including former Unity Pro)cisa_csaf_otUS
Schneider Electric Software, LLC EcoStruxure Process Expert< 2021 (including former HDCS)cisa_csaf_otUS
Schneider Electric Software, LLC SCADAPack RemoteConnect for x70< R2.7.3cisa_csaf_otUS
n/a AT&T≤ AT&T Labs Xmill 0.7, Schneider Electric EcoStruxure Control Expert 15enisa_euvdEU
AT&T Labs Xmill≤ 0.7fstec_bduRU
Schneider Electric EcoStruxure Control Expert≤ 15.1 HF001fstec_bduRU
Schneider Electric EcoStruxure Process Expert≤ 2021fstec_bduRU
Schneider Electric SCADAPack RemoteConnect≤ R2.7.3fstec_bduRU
att xmill= 0.7nvdUScpe:2.3:a:att:xmill:*:*:*:*:*:*:*:*

advisories (1)

Vendor and ecosystem advisories describing this.

ICSA-22-223-03Schneider Electric EcoStruxure, EcoStruxure Process Expert, SCADAPack RemoteConnect for x702022-08-11icsa · cisa_csaf_otUS
The successful exploitation of these vulnerabilities on the affected products could lead to the execution of malicious files, which could result in code execution with elevated privileges.

also known as (5)

Other names and identifiers for this entity.

sources

Which sources assert this record, and when.

cnnvd enisa_euvd fstec_bdu cisa_csaf_ot nvd NVD CVE.org MITRE

published 2021-08-20modified 2026-06-17

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+16132 more

references (7)

External citations — patches, advisories, analysis.

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