Security readout for executives and security teams
Plain-English summary
This issue affects certain Cisco IP phones. An attacker already on the same local network segment could send malicious discovery-protocol traffic that may crash a phone or execute code on it. It is not internet-routable, but it matters for offices where VoIP networks are reachable by untrusted devices.
Executive priority
Treat as a moderate internal-network risk. Prioritize sites where IP phones share local network access with unmanaged devices, guest ports, or weak segmentation. Patch through normal change control, with higher urgency for sensitive offices or exposed voice VLANs.
Technical view
CVE-2021-1379 is caused by missing checks in Cisco Discovery Protocol and LLDP packet handling on affected Cisco IP Phone Series 68xx/78xx/88xx software. It is unauthenticated but Layer 2 adjacent, scored CVSS 3.1 6.5, and mapped to CWE-120. Cisco released software updates and states there are no workarounds.
Likely exposure
Exposure is most likely in environments running affected Cisco IP phone firmware on shared VoIP VLANs or broadcast domains. Risk increases where visitor, workstation, or contractor devices can reach the same Layer 2 segment as phones.
Exploitation context
The provided sources do not show active exploitation, and the CVE is not marked KEV. Exploitation requires Layer 2 adjacency to the target phone, limiting reach compared with internet-facing vulnerabilities but still relevant for internal network compromise scenarios.
Researcher notes
Evidence supports adjacent unauthenticated RCE or DoS through CDP/LLDP parsing defects. The bundle does not provide exploit details, observed exploitation, or workaround options. Validation should focus on firmware matching, Layer 2 placement, and whether untrusted devices can send discovery traffic to phones.
Mitigation direction
- Apply Cisco software updates for affected IP phone models and firmware trains.
- Check Cisco guidance for exact fixed versions before scheduling upgrades.
- Segment voice networks from user and guest access where operationally feasible.
- Review switch controls that limit unauthorized devices on VoIP broadcast domains.
Validation and detection
- Inventory Cisco IP phones and record model, firmware, and software train.
- Compare deployed versions with Cisco affected-version guidance.
- Confirm phones are not reachable from untrusted Layer 2 segments.
- Document upgrade status and any devices awaiting vendor-supported remediation.
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 lookupExecution behavior lookup
The CVE wording references code or command execution, so execution technique review may help defensive triage. This is a Glexia inferred lookup path, not an official MITRE, ATT&CK, or CVE Program mapping.
Open ATT&CK lookupCVE-2021-1379 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
- 6.5 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H/RL:X/RC:X/E:X
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:N/A:H/RL:X/RC:X/E:X2.83.6Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
6.5MediumVector: CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H/RL:X/RC:X/E:X
Source materials
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.
