Security readout for executives and security teams
Plain-English summary
This vulnerability can let an unauthenticated network attacker crash affected Schneider Electric Modicon controller or communication-module web services with a specially crafted HTTP request. The business impact is availability loss in industrial environments, not data theft. Systems with reachable device web servers deserve prompt review.
Executive priority
Treat as high priority for exposed OT assets because exploitation requires no credentials and can disrupt device availability. Highest urgency belongs to production controllers reachable beyond tightly controlled OT management networks.
Technical view
CVE-2021-22787 is CWE-20 improper input validation in affected Modicon web servers. CVSS 3.1 is 7.5, network exploitable, low complexity, no privileges, no user interaction, with high availability impact and no stated confidentiality or integrity impact.
Likely exposure
Exposure is most likely where affected Modicon M340, Premium, or Quantum CPUs or Ethernet modules have their embedded web server reachable from enterprise, remote-access, vendor, or untrusted networks.
Exploitation context
The provided sources do not show CISA KEV listing or other evidence of active exploitation. The attack path is network-based HTTP denial of service, so reachability to the device web server is the key risk factor.
Researcher notes
Do not assume compromise or code execution from the supplied evidence. The documented impact is denial of service via crafted HTTP traffic against affected device web servers. Evidence is incomplete on public exploit activity and product-specific remediations beyond the affected version statements.
Mitigation direction
- Identify affected Modicon models and firmware versions in OT inventories.
- Check Schneider Electric advisory SEVD-2021-257-02 for supported fixes or workarounds.
- Prioritize BMXP34 CPUs running versions earlier than V3.40 for vendor-supported update review.
- Restrict access to device web servers to trusted management networks only.
- Reduce unnecessary routing from enterprise, remote-access, and internet-facing networks to affected devices.
Validation and detection
- Match asset inventories against the affected model list in the CVE record.
- Confirm firmware versions, especially BMXP34 CPUs below V3.40.
- Review network paths to determine whether embedded web servers are reachable.
- Check monitoring for unexplained device web-service crashes or availability drops.
- Verify remediation decisions against the Schneider Electric advisory.
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-20: Exact CWE lookup
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Open ATT&CK lookupCVE-2021-22787 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.
Improper Input Validation
Improper Input Validation represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.