Security readout for executives and security teams
Plain-English summary
Certain Cisco IP phones can be forced to reboot by unauthenticated network traffic, briefly disrupting calling availability. The issue affects availability, not data confidentiality or integrity. Business urgency is highest where these phones support contact centers, emergency response, operations, or executive communications.
Executive priority
Treat as a high-priority availability risk for voice services, not a data breach issue. Patch and segmentation work should be prioritized where phone downtime has operational, safety, or customer-service impact.
Technical view
CVE-2019-1635 is a SIP software flaw in Cisco IP Phone call-handling. Incomplete error handling while parsing XML data inside SIP traffic can cause affected 7800, 8800, 8821, and 8821-EX phones to reload unexpectedly, creating temporary DoS. CVSS 3.0 is 7.5, network exploitable, low complexity, no privileges, no user interaction.
Likely exposure
Exposure is most likely in organizations using Cisco IP Phone 7800 Series, 8800 Series, Wireless IP Phone 8821, or 8821-EX with affected SIP software, especially if phones can receive SIP traffic from untrusted or poorly segmented networks.
Exploitation context
The provided bundle does not identify CISA KEV listing or confirmed active exploitation. Cisco and CVE describe unauthenticated remote exploitability and temporary denial of service through malformed SIP/XML handling, but no public exploit status is established here.
Researcher notes
The weakness is tied to incomplete error handling during XML parsing in SIP call-handling logic and maps to CWE-399 in the bundle. Evidence is limited to CVE and Cisco advisory data; fixed-version specifics must be taken from Cisco guidance.
Mitigation direction
- Review Cisco advisory for affected and fixed software details.
- Upgrade affected Cisco IP phones according to Cisco guidance.
- Restrict SIP access to trusted voice infrastructure only.
- Segment voice networks from untrusted user and internet-facing networks.
- Monitor for unexpected phone reloads in high-availability calling areas.
Validation and detection
- Inventory Cisco phone models and SIP software versions.
- Compare deployed versions against the Cisco advisory.
- Verify phones cannot receive SIP traffic from untrusted networks.
- Review voice logs for repeated unexpected phone reloads.
- Prioritize validation for contact centers and emergency communications areas.
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-399: 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-2019-1635 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 (3.0)
- Known Exploited
- No
- Published
Vector: CVSS:3.0/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.
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:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H3.93.6Primary CVE scoreVulnerability scoring details
Base CVSS 3.0 score
7.5HighVector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Source materials
- CVE List V5 sourceCVE List V5
- 20190501 Cisco IP Phone 7800 Series and 8800 Series Session Initiation Protocol XML Denial of Service VulnerabilityCVE 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.
Resource Management Errors
Resource Management Errors represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.