Security readout for executives and security teams
Plain-English summary
This issue affects Cisco Small Business Smart Switches through their LLDP handling. An attacker on the same local network segment could corrupt LLDP data and, according to Cisco’s description, potentially cause code execution or unexpected reloads. It is not internet-routable by design, but local network access makes exposed office, branch, or shared network environments relevant.
Executive priority
Treat as a moderate infrastructure maintenance issue, not a public internet emergency. Remediate affected switches during normal patch cycles, faster where untrusted users can access the same local network.
Technical view
CVE-2021-34775 covers multiple LLDP implementation flaws in Cisco Small Business 220 Series Smart Switches. The CVSS vector is AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N with score 4.3. The listed CWE is CWE-120. Exploitation requires Layer 2 adjacency in the same broadcast domain. Cisco released firmware updates.
Likely exposure
Likely exposure is limited to organizations running affected Cisco Small Business Smart Switches where an attacker can join the same Layer 2 broadcast domain. The source bundle is inconsistent: the title and description say 220 Series, while the affected product field says 200 Series. Verify exact models against Cisco’s advisory.
Exploitation context
The bundle does not show CISA KEV listing or cited evidence of active exploitation. The main constraint is adjacency: the attacker must already be on the same local network segment as the switch. No remote internet attack path is supported by the supplied sources.
Researcher notes
Key technical constraints are LLDP parsing, unauthenticated adjacent access, and same-broadcast-domain reachability. The CVSS score is modest despite Cisco’s broader impact language. Do not assume exploit availability or affected models beyond the advisory without additional evidence.
Mitigation direction
- Apply Cisco firmware updates that address this advisory.
- Verify exact affected models and fixed versions in Cisco’s advisory.
- Reduce untrusted access to switch broadcast domains where feasible.
- Prioritize branches, shared offices, labs, and guest-accessible network areas.
Validation and detection
- Inventory Cisco Small Business Smart Switch models and firmware versions.
- Check whether listed devices match Cisco’s affected-product guidance.
- Confirm LLDP exposure on networks reachable by untrusted users.
- Document firmware remediation status for every affected switch.
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 lookupDatabase behavior lookup
The CVE wording references database injection or access, so collection and exfiltration review may help. This is a Glexia inferred lookup path, not an official MITRE, ATT&CK, or CVE Program mapping.
Open ATT&CK lookupCVE-2021-34775 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
- Medium
- CVSS
- 4.3 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
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:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N2.81.4Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
4.3MediumVector: CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
Source materials
- CVE List V5 sourceCVE List V5
- 20211006 Cisco Small Business 220 Series Smart Switches Link Layer Discovery Protocol VulnerabilitiesCVE reference · vendor-advisory, x_refsource_CISCO
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.