Security readout for executives and security teams
Plain-English summary
This issue affects Cisco Small Business 220 Series Smart Switches using LLDP. An attacker on the same local Layer 2 network could disrupt LLDP data and, according to Cisco, may execute code or force a reload. It is not remotely exploitable over the internet by itself.
Executive priority
Treat as a targeted local-network risk, not an internet-wide emergency. Prioritize firmware updates for exposed branch or shared-access networks, especially where guest, contractor, lab, or compromised endpoint access could place an attacker on the same broadcast domain.
Technical view
CVE-2021-34780 is a set of LLDP implementation flaws in Cisco Small Business 220 Series Smart Switches. The CVSS 3.1 vector is AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N with score 4.3. The source bundle lists CWE-120 and notes Cisco firmware updates address the issue.
Likely exposure
Exposure is limited to affected Cisco Small Business switches reachable by an unauthenticated attacker in the same broadcast domain. Public inventory should focus on branch, small office, lab, and unmanaged-adjacent network segments where untrusted devices share Layer 2 access.
Exploitation context
The source bundle provides no KEV listing and no cited evidence of active exploitation. Exploitation requires Layer 2 adjacency because LLDP is a Layer 2 protocol. This reduces internet-scale risk but matters where attackers can join the local network.
Researcher notes
The record has a product-label inconsistency: the title and description reference Small Business 220 Series, while affected metadata says 200 Series. Use Cisco’s advisory as the authoritative source before scoping. Do not assume exploitability beyond Layer 2 adjacency from the provided evidence.
Mitigation direction
- Apply Cisco firmware updates referenced in the vendor advisory.
- Verify affected switch models and firmware against Cisco guidance.
- Reduce untrusted Layer 2 adjacency to affected switches.
- Review LLDP exposure where untrusted devices share broadcast domains.
- Monitor Cisco advisory updates for revised affected software details.
Validation and detection
- Inventory Cisco Small Business 220 Series Smart Switches.
- Check firmware versions against Cisco fixed-release guidance.
- Map VLANs and broadcast domains with untrusted device access.
- Confirm LLDP-related behavior after firmware update.
- Document any source discrepancy between 220 Series title and 200 Series metadata.
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-2021-34780 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.