Security readout for executives and security teams
Plain-English summary
This CVE is a memory-corruption flaw in AT&T Labs Xmill 0.7 XML decompression, also listed with Schneider Electric EcoStruxure Control Expert 15. A malicious XMI file can trigger a heap buffer overflow. Successful exploitation could affect confidentiality, integrity, and availability.
Executive priority
Prioritize assessment where affected software touches engineering, automation, or file-ingestion workflows. The risk is high because memory corruption could enable severe impact, but evidence of active exploitation is not provided.
Technical view
DecodeTreeBlock trusts a UINT32 length read from an XMI file and uses it for buffer handling during decompression. That creates a heap-based buffer overflow condition classified as CWE-120. The CVSS 3.0 score is 8.1 with high impact to confidentiality, integrity, and availability.
Likely exposure
Exposure is most likely where AT&T Labs Xmill 0.7 or Schneider Electric EcoStruxure Control Expert 15 processes untrusted or externally supplied XMI/XML-compressed files, especially in automated import or engineering workflows.
Exploitation context
The supplied sources describe malicious-file triggering and CVSS network reachability, but provide no KEV listing and no cited evidence of active exploitation. Treat exploit status as unconfirmed from this bundle.
Researcher notes
The affected-product data in the bundle is imprecise, so verify product mapping carefully. The record says malicious XMI triggers the issue, while the CVSS vector lists network attack and no user interaction. Do not assume patch availability from these sources alone.
Mitigation direction
- Inventory systems using the listed Xmill or EcoStruxure Control Expert versions.
- Check Talos and vendor guidance for fixed versions or supported mitigations.
- Avoid processing untrusted XMI files on affected systems.
- Restrict file intake paths to trusted sources only.
- Isolate vulnerable processing hosts from high-value networks.
- Monitor for decompression crashes or unexpected process failures.
Validation and detection
- Confirm whether listed versions are installed or bundled in local products.
- Identify workflows that automatically decompress or import XMI files.
- Review vulnerability scanner findings against the exact affected versions.
- Check logs for crashes during XML or XMI decompression.
- Verify vendor guidance before declaring remediation complete.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
CWE-120: Exact CWE lookup
Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupCVE-2021-21826 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- High
- CVSS
- 8.1 (3.0)
- Known Exploited
- No
- Published
Vector: CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
CVSS vector scores
1 official scoreWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H2.25.9Primary CVE scoreVulnerability scoring details
Base CVSS 3.0 score
8.1HighVector: CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
Source materials
- CVE List V5 sourceCVE List V5
- https://talosintelligence.com/vulnerability_reports/TALOS-2021-1291CVE reference · x_refsource_MISC
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.
Buffer Copy without Checking Size of Input ('Classic Buffer Overflow')
Buffer Copy without Checking Size of Input ('Classic Buffer Overflow') represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.