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Full vulnerability report · 2016
CVE-2016-6455High confidence

n/a Cisco StarOS 18.x through 21.x: security vulnerability

Unknown · Cisco StarOS 18.x through 21.x

Official source article: Cisco CISCO-SA-20161102-ASR ↗. Check the applicable product and release in the original source.

7.5HighCVSS 3.0
Recommended action
Within 7 days

High technical severity; prioritise exposed affected systems while verifying vendor guidance.

Fix not verified
R
Operational reassessment

Published severity in operational context

Open reassessment dashboard →
Published severityHighOperational priority:High, unchanged from published severity.unchanged

Evidence used

  • No CISA KEV confirmation is currently recorded.
  • The selected CVSS metric records a network-reachable, unauthenticated path with no user interaction.
  • EPSS is 1.75% for the current model date.

Compensating controls

  • Restrict the affected network interface to trusted sources where business-safe.
  • Monitor vendor guidance and exploitation sources for a material change.

Verification

  1. Confirm that the asset runs Unknown Cisco StarOS 18.x through 21.x and falls inside the recorded affected range.
  2. Recheck the vendor advisory before scheduling a change because no verified fixed version is currently retained.
  3. Validate exposure, authentication requirements and compensating controls in the actual environment.
  4. Reopen this reassessment when CVSS, KEV, EPSS, exploit evidence or remediation changes.
Mitigation target: Within 30 daysRemediation target: Within 180 days

This automated reassessment organises public evidence. It does not know asset exposure, business impact or control effectiveness and does not replace CVSS or a human risk decision.

Optional official sources

National CERT insights
?CERT means Computer Emergency Response Team; CSIRT is the closely related term Computer Security Incident Response Team.

Choose official national sources for this report. Each advisory shows its original language. Your selection is remembered on this device and included in shared links.

Official European source

ENISA European Vulnerability Database

Official EUVD identifiers, advisory evidence and known-exploited context. Missing fields are not treated as evidence of low risk.

1 current
ENISA EUVD identifier

EUVD-2016-7378

No EUVD known-exploited evidence

ENISA has published the identifier mapping but no EUVD description has been stored yet.

EUVD state
Present in the current official mapping
Known exploitation
Not present in the current ENISA EUVD known-exploited dataset. This is not proof of no exploitation.
ENISA score
Not supplied in the stored EUVD record
Advisory evidence
No linked advisory details stored yet
Recommended actionWithin 7 days

High technical severity; prioritise exposed affected systems while verifying vendor guidance.

Fix not verified
01

What, why and how

A vulnerability in the Slowpath of StarOS for Cisco ASR 5500 Series routers with Data Processing Card 2 (DPC2) could allow an unauthenticated, remote attacker to cause a subset of the subscriber sessions to be disconnected, resulting in a partial denial of service (DoS) condition. This vulnerability affects Cisco ASR 5500 devices with Data Processing Card 2 (DPC2) running StarOS 18.0 or later. More Information: CSCvb12081. Known Affected Releases: 18.7.4 19.5.0 20.0.2.64048 20.2.3 21.0.0. Known Fixed Releases: 18.7.4 18.7.4.65030 18.8.M0.65044 19.5.0 19.5.0.65092 19.5.M0.65023 19.5.M0.65050 20.2.3 20.2.3.64982 20.2.3.65017 20.2.a4.65307 20.3.M0.64984 20.3.M0.65029 20.3.M0.65037 20.3.M0.65071 20.3.T0.64985 20.3.T0.65031 20.3.T0.65043 20.3.T0.65067 21.0.0 21.0.0.65256 21.0.M0.64922 21.0.M0.64983 21.0.M0.65140 21.0.V0.65150 21.1.A0.64932 21.1.A0.64987 21.1.A0.65145 21.1.PP0.65270 21.1.R0.65130 21.1.R0.65135 21.1.R0.65154 21.1.VC0.65203 21.2.A0.65147.

What

A vulnerability in the Slowpath of StarOS for Cisco ASR 5500 Series routers with Data Processing Card 2 (DPC2) could allow an unauthenticated, remote attacker to cause a subset of the subscriber sessions to be disconnected, resulting in a partial denial of service (DoS) condition. This vulnerability affects Cisco ASR 5500 devices with Data Processing Card 2 (DPC2) running StarOS 18.0 or later. More Information: CSCvb12081. Known Affected Releases: 18.7.4 19.5.0 20.0.2.64048 20.2.3 21.0.0. Known Fixed Releases: 18.7.4 18.7.4.65030 18.8.M0.65044 19.5.0 19.5.0.65092 19.5.M0.65023 19.5.M0.65050 20.2.3 20.2.3.64982 20.2.3.65017 20.2.a4.65307 20.3.M0.64984 20.3.M0.65029 20.3.M0.65037 20.3.M0.65071 20.3.T0.64985 20.3.T0.65031 20.3.T0.65043 20.3.T0.65067 21.0.0 21.0.0.65256 21.0.M0.64922 21.0.M0.64983 21.0.M0.65140 21.0.V0.65150 21.1.A0.64932 21.1.A0.64987 21.1.A0.65145 21.1.PP0.65270 21.1.R0.65130 21.1.R0.65135 21.1.R0.65154 21.1.VC0.65203 21.2.A0.65147.

Why

The current structured CVE record identifies a security weakness, but the root cause requires confirmation in the linked vendor material.

How

An attacker operating through a network path may attempt exploitation without authentication or user interaction. If successful, the issue may disrupt the affected service.

What

A vulnerability in the Slowpath of StarOS for Cisco ASR 5500 Series routers with Data Processing Card 2 (DPC2) could allow an unauthenticated, remote attacker to cause a subset of the subscriber sessions to be disconnected, resulting in a partial denial of service (DoS) condition. This vulnerability affects Cisco ASR 5500 devices with Data Processing Card 2 (DPC2) running StarOS 18.0 or later. More Information: CSCvb12081. Known Affected Releases: 18.7.4 19.5.0 20.0.2.64048 20.2.3 21.0.0. Known Fixed Releases: 18.7.4 18.7.4.65030 18.8.M0.65044 19.5.0 19.5.0.65092 19.5.M0.65023 19.5.M0.65050 20.2.3 20.2.3.64982 20.2.3.65017 20.2.a4.65307 20.3.M0.64984 20.3.M0.65029 20.3.M0.65037 20.3.M0.65071 20.3.T0.64985 20.3.T0.65031 20.3.T0.65043 20.3.T0.65067 21.0.0 21.0.0.65256 21.0.M0.64922 21.0.M0.64983 21.0.M0.65140 21.0.V0.65150 21.1.A0.64932 21.1.A0.64987 21.1.A0.65145 21.1.PP0.65270 21.1.R0.65130 21.1.R0.65135 21.1.R0.65154 21.1.VC0.65203 21.2.A0.65147.

Why

The current structured CVE record identifies a security weakness, but the root cause requires confirmation in the linked vendor material.

How

An attacker operating through a network path may attempt exploitation without authentication or user interaction. If successful, the issue may disrupt the affected service.

02

Exploit reality and attack path

CVSS severity, EPSS forecast probability, public exploit material and CISA-confirmed exploitation are separate signals.

Observed exploitation
?Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.
No confirmed evidence

No CISA KEV match was present at the last successful refresh. This means no confirmation from that source, not proof of no exploitation.

Public PoC / exploit material
?Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.
None recorded

No exploit-tagged reference or CISA SSVC proof-of-concept state is currently recorded. Research may still exist outside the structured feeds.

Likely attack path
a network path → vulnerable operation → disrupt the affected service
Attack surface
Network
Privileges required
None: unauthenticated exploitation is possible
User interaction
None
Attack complexity
Low: no specialised conditions are recorded
Security boundary
Unchanged: impact remains within the vulnerable component's security authority
Weakness
?CWE means Common Weakness Enumeration: a standard category for the underlying weakness.
CWE-399 ↗

CWE-399. Open the MITRE definition for the exact weakness description.

CVSS vector
?CVSS means Common Vulnerability Scoring System. The vector records the metric values used to calculate technical severity.
CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Common Vulnerability Scoring System 3.0: the compact vector below is decoded into plain language.

AVNetworkAttack vector: The vulnerable component can be reached over a network.ACLowAttack complexity: No specialised conditions are required beyond attacker-controlled input.PRNonePrivileges required: The attacker does not need an account or existing privileges.UINoneUser interaction: No action by another user is required.SUnchangedScope: The security impact remains within the vulnerable component's authority.CNoneConfidentiality impact: No direct loss is represented by this metric.INoneIntegrity impact: No direct loss is represented by this metric.AHighAvailability impact: A successful attack can cause a major loss.
Post-exploitation / living off the land
No specific living-off-the-land technique is confirmed in the structured sources. Monitor normal administration tools for activity inconsistent with the affected service's baseline.
NetworkUnauthenticatedDenial of serviceCWE-399
A

Official authority intelligence

Only matched European and national findings are included. Language selectors and unavailable sources are omitted.

Canadian Centre for Cyber Security · English · AV16-181Cisco Releases security updates

Cisco released multiple security updates to address vulnerabilities (critical to medium) in Cisco ASR 900 Series Aggregation Services Routers, Cisco Prime Home, Cisco Meeting Server, Cisco Meeting App, Cisco ASR 5500 Series Routers, Cisco Email Security Appliance and Cisco TelePresence Endpoints. CVE References: Critical Impact CVEs: CVE-2016-6441, CVE-2016-6452 High Impact CVEs: CVE-2016-6447, CVE-2016-6448 Medium Impact CVEs: CVE-2016-6455, CVE-2016-6457, CVE-2016-6458, CVE-2016-6459

Official advisory ↗
CERT-FR · French · CERTFR-2016-AVI-366Multiples vulnérabilités dans les produits Cisco

De multiples vulnérabilités ont été corrigées dans les produits Cisco . Elles permettent à un attaquant de provoquer une exécution de code arbitraire à distance, un déni de service à distance et un contournement de la politique de sécurité.

Official advisory ↗
JVN iPedia · Japanese · JVNDB-2016-005737Data Processing Card 2 を伴う Cisco ASR 5000 シリーズルータの StarOS における加入者セッションの一部を切断される脆弱性

Data Processing Card 2 (DPC2) を伴う Cisco ASR 5000 シリーズルータの StarOS の Slowpath には、加入者セッションの一部 (subset) を切断され、その結果、サービス運用妨害 (DoS) 状態にされる脆弱性が存在します。 ベンダは、本脆弱性を Bug ID CSCvb12081 として公開しています。

Official advisory ↗
KISA KrCERT/CC · Korean · KNVD-4668Cisco 제품군 취약점 보안 업데이트 권고

Cisco DPC2 ASR 5500 라우터에서 발생하는 서비스 거부 취약점(CVE-2016-6455) [9]

Official advisory ↗
03

Patch and workaround

Operational remediation based on structured source evidence.

Status
?Patch availability is based on structured fixed-version fields and authoritative update references. If no fix is verified, check the vendor advisory before making a change.
Fix not verified
Affected
Cisco StarOS 18.x through 21.x: Cisco StarOS 18.x through 21.x
Fixed
No fixed version is explicitly recorded in the structured CVE data.
Action
No verified patch reference is present in the current structured sources. Check the vendor advisory before making a change.
Workaround
No verified workaround is recorded. If business-safe, reduce exposure to the affected interface and allow only trusted sources until authoritative guidance is available.
04

Evidence and provenance

Published 3 Nov 2016 · Last source change 6 Aug 2024, 01:29 UTC · CWE-399

CVE recordCVE.org · 5.1
CVSS sourceNIST NVD
EPSS source
?The date BlackTree first stored a score for this CVE from the daily FIRST EPSS feed.
FIRST · tracked since 2026-09-01
European sourceENISA EUVD · EUVD-2016-7378
Product sourceCNA
Remediation sourceCVE/CNA references
CWE sourceNIST NVD
NVD statusNVD modified after enrichment

Missing structured fields: affected product. Missing data is not evidence of low risk; review the primary advisory.

Material change intelligence

What changed after publication

View recent updates ↗
  1. ENISA EUVD mappingEUVD-2016-7378 was added to the official ENISA EUVD mapping for this CVE.
    Before
    not recorded
    After
    {"euvdId":"EUVD-2016-7378"}
    ENISA EUVD ↗
  2. Vendor guidanceAuthoritative vendor guidance changed: added vendor advisory: tools.cisco.com/cisco-sa-20161102-asr.
    Before
    no authoritative guidance recorded
    After
    vendor advisory: tools.cisco.com/cisco-sa-20161102-asr
    tools.cisco.com ↗
  3. SeveritySeverity changed from Unknown to High.
    Before
    Unknown
    After
    High
    NIST NVD ↗
  4. CVSS scoreCVSS score changed from not recorded to 7.5 (CVSS 3.0 · NIST NVD · CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H).
    Before
    not recorded
    After
    7.5 (CVSS 3.0 · NIST NVD · CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H)
    NIST NVD ↗
  5. Catalogue recordCVE added to the BlackTree catalogue.
    CNA ↗
Material fields only · duplicate refreshes suppressed · history retained for the configured operational retention period
CVE published
ENISA EUVD · EUVD-2016-7378↗Vendor advisory · Cisco CISCO-SA-20161102-ASR↗CVE authority or vendor reference↗Official CVE record (CNA and ADP data)↗NVD record↗
Technical terms and abbreviations used in this report
CVE
Common Vulnerabilities and Exposures: the public identifier for one disclosed vulnerability.
CVSS
Common Vulnerability Scoring System: a technical severity framework; it is not patching priority by itself.
EPSS
Exploit Prediction Scoring System: FIRST's estimate of the probability that exploitation activity will be observed in the next 30 days; it is a forecast, not confirmation.
CWE
Common Weakness Enumeration: the standard category describing the underlying software or hardware weakness.
CNA
CVE Numbering Authority: an organisation authorised to assign and publish CVE records.
CISA ADP
Cybersecurity and Infrastructure Security Agency Authorized Data Publisher: structured enrichment added to a CVE record.
NVD
National Vulnerability Database: NIST's enrichment service for CVE records.
CERT / CSIRT
A computer security incident response team that publishes warnings or coordinates incident response.
PoC
Proof of concept: public material that demonstrates or helps reproduce exploitation.
CSAF
Common Security Advisory Framework: a machine-readable format for security advisories.
LoTL
Living off the land: abuse of legitimate tools or system functions during an attack.
Free version - for non-commercial use only.CVE-2016-6455 · cve.blacktree.nl