Security readout for executives and security teams
Plain-English summary
This vulnerability can let an unauthenticated network attacker crash affected Modicon PLC or Ethernet communication devices by sending a specially crafted HTTP request to the device web server. The business impact is availability: production visibility or control equipment may require recovery if exposed and triggered.
Executive priority
Prioritize this for OT environments where affected Modicon devices support production processes. It is not described as data theft or code execution, but unauthenticated network-triggered denial of service can disrupt operations if web interfaces are reachable.
Technical view
CVE-2021-22788 is a CWE-787 out-of-bounds write in affected Modicon device web servers. CVSS 3.1 is 7.5: network exploitable, low complexity, no privileges, no user interaction, unchanged scope, availability impact only. The affected list includes M340, Premium, and Quantum CPU or communication modules.
Likely exposure
Exposure is most likely where affected Modicon device web servers are reachable from corporate networks, remote access paths, vendor access, or the internet. Sites using listed M340, Premium, or Quantum models should treat HTTP management access as the key exposure point.
Exploitation context
The provided bundle does not show CISA KEV listing or cited evidence of active exploitation. The source states exploitation requires a specially crafted HTTP request to the device web server and may cause denial of service.
Researcher notes
Evidence is limited to the CVE record and Schneider advisory reference in the bundle. Treat the affected product list carefully: some families are version-bounded, while several modules are listed as all versions affected. Do not assume exploit availability or universal patches without vendor guidance.
Mitigation direction
- Inventory listed Modicon M340, Premium, and Quantum CPUs and communication modules.
- Review Schneider Electric advisory SEVD-2021-257-02 for product-specific fixes or workarounds.
- Upgrade BMXP34 M340 CPUs beyond affected versions where vendor guidance supports it.
- Restrict device web server access to trusted engineering or management networks.
- Disable or firewall unnecessary HTTP access where operationally feasible.
- Monitor affected devices for web server crashes or unexpected restarts.
Validation and detection
- Compare device model and firmware against the affected product list.
- Confirm whether each device web server is enabled and network reachable.
- Verify segmentation blocks HTTP access from untrusted networks.
- Check OT monitoring for unexplained device denial-of-service symptoms.
- Document vendor advisory status for all models listed as all versions affected.
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-787: 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-2021-22788 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
- 7.5 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/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.
SSVC decision data
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:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H3.93.6CISA-ADPVulnerability scoring details
Base CVSS 3.1 score
7.5HighVector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Vulnerability timeline
Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.
- CVE reservedCVE Program
The CVE ID was reserved by the assigning CNA.
- CVE publishedCVE Program
The CVE record was published.
- CVE updatedCVE Program
The CVE record metadata indicates this as the latest update time.
ADP provider summaries
Source materials
- CVE List V5 sourceCVE List V5
- https://download.schneider-electric.com/files?p_Doc_Ref=SEVD-2021-257-02CVE reference, schneider · 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.
Out-of-bounds Write
Out-of-bounds Write represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.