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CVE Record

CVE-2021-0250: Junos OS and Junos OS Evolved: An attacker sending a specific crafted BGP update message will crash RPD

In segment routing traffic engineering (SRTE) environments where the BGP Monitoring Protocol (BMP) feature is enable, a vulnerability in the Routing Protocol Daemon (RPD) process of Juniper Networks Junos OS allows an attacker to send a specific crafted BGP update message causing the RPD service to core, creating a Denial of Service (DoS) Condition. Continued receipt and processing of this update message will create a sustained Denial of Service (DoS) condition. This issue affects IPv4 and IPv6 environments. This issue affects: Juniper Networks Junos OS 17.4 versions 17.4R1 and above prior to 17.4R2-S6, 17.4R3; 18.1 versions prior to 18.1R3-S7; 18.2 versions prior to 18.2R2-S6, 18.2R3-S3; 18.3 versions prior to 18.3R1-S7, 18.3R2-S3, 18.3R3; 18.4 versions prior to 18.4R1-S5, 18.4R2-S3, 18.4R3; 19.1 versions prior to 19.1R1-S4, 19.1R2; 19.2 versions prior to 19.2R1-S3, 19.2R2, This issue does not affect Junos OS releases prior to 17.4R1. This issue affects: Juniper Networks Junos OS Evolved 19.2-EVO versions prior to 19.2R2-EVO.

HighCVSS 7.5Not KEV-listedUpdated
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Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

This is a network-facing denial-of-service flaw in Juniper routing software. In SRTE deployments with BMP enabled, a crafted BGP update can crash the routing protocol daemon. Repeated messages can keep routing services down, disrupting network availability rather than exposing data.

Executive priority

Prioritize remediation for affected Juniper routers that support critical routing paths or external BGP adjacency. The issue is availability-focused but can create sustained routing disruption if vulnerable devices repeatedly process the triggering update.

Technical view

CVE-2021-0250 affects RPD in Junos OS and Junos OS Evolved when Segment Routing Traffic Engineering and BGP Monitoring Protocol are in use. The CVSS 3.1 vector shows unauthenticated network-triggered availability impact across IPv4 and IPv6.

Likely exposure

Exposure is limited to Juniper Junos OS 17.4R1 and later through specified unfixed 19.2 trains, and Junos OS Evolved 19.2-EVO before 19.2R2-EVO, in SRTE environments with BMP enabled. Releases before 17.4R1 are stated as unaffected.

Exploitation context

The provided sources describe a specific crafted BGP update message causing RPD to core. They do not identify public exploit code, exploitation in the wild, or CISA KEV listing. Treat peer-reachable BGP control planes as higher urgency.

Researcher notes

The source bundle is specific about feature prerequisites, affected trains, and fixed version thresholds. It does not include exploit telemetry, proof-of-concept status, or detailed packet conditions. Validation should focus on feature exposure, version state, and RPD stability indicators.

Mitigation direction

  • Upgrade Junos OS to a fixed release listed in Juniper advisory JSA11143.
  • Upgrade Junos OS Evolved 19.2-EVO systems to 19.2R2-EVO or later.
  • Confirm whether BMP is enabled in SRTE environments and prioritize those devices.
  • Check Juniper guidance for any deployment-specific workarounds or operational constraints.

Validation and detection

  • Inventory Junos OS and Junos OS Evolved versions against the affected release ranges.
  • Identify routers using Segment Routing Traffic Engineering with BMP enabled.
  • Review RPD crash logs or core files for unexplained routing daemon failures.
  • Verify fixed software versions after maintenance windows complete.
Prepared
Confidence
high
Sources
3

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

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.

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CVE-2021-0250 mapping review

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Vulnerability profileCVE Program record
Severity
High
CVSS
7.5 (3.1)
Known Exploited
No
Published

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Official CVE source material

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.

1CVSS vectors
0Timeline events
0ADP providers
2Source links

CVSS vector scores

1 official score

We 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.

ScoreVersionSeverityVectorExploitImpactSource
7.5CVSS 3.1HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H3.93.6Primary CVE score

Vulnerability scoring details

Base CVSS 3.1 score

7.5High
CVSS 3.1 vector shape for CVE-2021-0250Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Attack Vector
NetworkAdjacentLocalPhysical
Attack Complexity
LowHigh
Privileges Required
NoneLowHigh
User Interaction
NoneRequired
Scope
ChangedUnchanged
Confidentiality Impact
HighLowNone
Integrity Impact
HighLowNone
Availability Impact
HighLowNone

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
Juniper NetworksJunos OS17.4R1, 17.4, 18.1, 18.2, 18.3, 18.4, 19.1, 19.2Listed
Juniper NetworksJunos OS Evolved19.2-EVOListed
Weakness

CWE details

No CWE listed

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