Security readout for executives and security teams
Plain-English summary
CVE-2021-1353 is a Cisco StarOS issue that can let a remote unauthenticated attacker crash a network function by exhausting memory with crafted IPv4 traffic. The business impact is service disruption, not data theft or tampering, based on the supplied CVSS vector.
Executive priority
Treat this as a moderate availability risk. It warrants planned remediation for affected Cisco StarOS environments, especially where service continuity is critical. It is not described as a confidentiality or integrity issue in the supplied sources.
Technical view
Cisco describes a memory leak in StarOS IPv4 packet processing. Crafted IPv4 packets sent through an affected device can exhaust memory and unexpectedly restart the npusim process, causing denial of service. CVSS 3.1 is 5.8 with network attack vector, low complexity, no privileges, and low availability impact.
Likely exposure
Exposure is limited to organizations running affected Cisco ASR 5000 Series Software or StarOS-based deployments that process IPv4 traffic through the vulnerable path. The provided sources do not identify specific vulnerable version ranges or deployment prerequisites beyond the Cisco product family.
Exploitation context
The source bundle says the attack is remote and unauthenticated, requiring crafted IPv4 packets through the affected device. It does not report public exploitation, and KEV status is false in the provided data. No exploit steps are needed to understand the operational risk.
Researcher notes
Evidence is strongest for the vulnerability class, impact, and attack requirements. The provided bundle lacks detailed affected versions, fixed releases, workarounds, and real-world exploitation evidence. Avoid assuming broader Cisco products are affected without the vendor advisory.
Mitigation direction
- Review Cisco advisory for affected releases, fixed software, and any supported workarounds.
- Inventory Cisco ASR 5000 Series Software and StarOS deployments handling IPv4 traffic.
- Prioritize remediation during maintenance windows for exposed carrier or edge packet-processing roles.
- Monitor memory pressure and unexpected npusim restarts until vendor guidance is applied.
Validation and detection
- Confirm whether Cisco ASR 5000 Series Software is present in the environment.
- Compare installed StarOS versions against the Cisco advisory guidance.
- Review device logs for memory exhaustion or unexpected npusim process restarts.
- Validate IPv4 traffic paths through potentially affected devices.
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-401: 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-2021-1353 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
- 5.8 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:L
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:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:L3.91.4Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
5.8MediumVector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:L
Source materials
- CVE List V5 sourceCVE List V5
- 20210120 Cisco StarOS IPv4 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.
Missing Release of Memory after Effective Lifetime
Missing Release of Memory after Effective Lifetime represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.