CASCACascade Atlas

Evidence dossier

CVE-2009-2055

Cisco IOS XR 3.4.0 through 3.8.1 allows remote attackers to cause a denial of service (session reset) via a BGP UPDATE message with an invalid attribute, as demonstrated in the…

Exploited in the wild (CISA KEV since Mar 25, 2022). NVD reports CVSS 2.0 4.3. EPSS estimates 3.3% exploit likelihood as of Aug 27, 2026.

57.0–58.6Priority evidence range
Evidence current through Aug 27, 2026, 6:09 PM UTC

As of Aug 27, 2026

Normalized restatement

Cisco IOS XR 3.4.0 through 3.8.1 allows remote attackers to cause a denial of service (session reset) via a BGP UPDATE message with an invalid attribute, as demonstrated in the wild on 17 August 2009.

State
PUBLISHED
Published
Aug 19, 2009
Updated
Jan 12, 2026
Evidence coverage
99%

Evidence chronology

What was known when

Download this view's receipt →
  1. Source dateSource date omittedFirst observed by CASCA
    CISA-ADP

    Record text: CISA ADP Vulnrichment

    Inspect raw assertion
    Field
    container
    Value
    CISA ADP Vulnrichment
    Original evidence ↗
  2. Source dateSource date omittedFirst observed by CASCA
    cisco

    Record text: Cisco IOS XR 3.4.0 through 3.8.1 allows remote attackers to cause a denial of service (session reset) via a BGP UPDATE message with an invalid attribute, as demonstrated in the wild on 17 August 2009.

    Inspect raw assertion
    Field
    container
    Value
    Cisco IOS XR 3.4.0 through 3.8.1 allows remote attackers to cause a denial of service (session reset) via a BGP UPDATE message with an invalid attribute, as demonstrated in the wild on 17 August 2009.
    Original evidence ↗
  3. Source dateSource date omittedFirst observed by CASCA
    CVE Program

    Record text: CVE Program Container

    Inspect raw assertion
    Field
    container
    Value
    CVE Program Container
    Original evidence ↗
  4. Source dateFirst observed by CASCA
    CISA KEV

    Exploitation cataloged: Cisco IOS XR Border Gateway Protocol (BGP) Denial-of-Service Vulnerability

    Inspect raw assertion
    Field
    observed_exploitation
    Value
    Cisco IOS XR Border Gateway Protocol (BGP) Denial-of-Service Vulnerability
    Original evidence ↗
  5. Source dateFirst observed by CASCA
    FIRST EPSS

    EPSS score: 3.33% probability · 87.71th percentile

    Inspect raw assertion
    Field
    model_probability
    Value
    Probability 0.033260000000; percentile 0.877090000000
    Original evidence ↗
ExploitationCatalog member

CISA KEV · catalog date Mar 25, 2022 · first observed Jul 19, 2026

Exploit likelihood3.33%

FIRST EPSS · score date Aug 27, 2026 · 87.7th percentile · first observed Aug 27, 2026

SeverityCVSS 4.3

NVD · CVSS 2.0 · first observed Jul 19, 2026 · same-version scores align in this snapshot

Evidence detail

Source limits and decisions

Why each evidence state has this value

casca-unknown-reasons-v1
Exploitation statusEvidence supported

Eligible evidence is present for this bounded claim.

Revision
evidence-policy-v1.1.0
Cutoff
Aug 27, 2026
Resolution
None
Exploit likelihoodEvidence supported

Eligible evidence is present for this bounded claim.

Revision
evidence-policy-v1.1.0
Cutoff
Aug 27, 2026
Resolution
None
Severity assessmentEvidence supported

Eligible evidence is present for this bounded claim.

Revision
casca-direct-cvss-eligibility-v1
Cutoff
Aug 27, 2026
Resolution
None
Affected productsSource-reported scope

The cited source assertion is retained while canonical product linkage remains open.

Revision
casca-factor-d-obligations-v1
Cutoff
Aug 27, 2026
Resolution
Resolve identity

Source comparison

Who said what

CISA-ADPIndependent enrichment
Record text

CISA ADP Vulnrichment

Inspect raw assertion
Field
container
Value
CISA ADP Vulnrichment
Source dateSource date omittedFirst observed by CASCAOriginal evidence ↗
ciscoOriginal assertion
Record text

Cisco IOS XR 3.4.0 through 3.8.1 allows remote attackers to cause a denial of service (session reset) via a BGP UPDATE message with an invalid attribute, as demonstrated in the wild on 17 August 2009.

Inspect raw assertion
Field
container
Value
Cisco IOS XR 3.4.0 through 3.8.1 allows remote attackers to cause a denial of service (session reset) via a BGP UPDATE message with an invalid attribute, as demonstrated in the wild on 17 August 2009.
Source dateSource date omittedFirst observed by CASCAOriginal evidence ↗
CVE ProgramDerivative copy
Record text

CVE Program Container

Inspect raw assertion
Field
container
Value
CVE Program Container
Source dateSource date omittedFirst observed by CASCAOriginal evidence ↗
CISA KEVOriginal assertion
Exploitation cataloged

Cisco IOS XR Border Gateway Protocol (BGP) Denial-of-Service Vulnerability

Inspect raw assertion
Field
observed_exploitation
Value
Cisco IOS XR Border Gateway Protocol (BGP) Denial-of-Service Vulnerability
Source dateFirst observed by CASCAOriginal evidence ↗
FIRST EPSSOriginal assertion
EPSS score

3.33% probability · 87.71th percentile

Inspect raw assertion
Field
model_probability
Value
Probability 0.033260000000; percentile 0.877090000000
Source dateFirst observed by CASCAOriginal evidence ↗

Applicability

Cited product scope

Trace impact →
19Underlying assertions
1Canonical products
19Target assertions
0Constraint assertions

Grouped from 1 configuration nodes in this exact snapshot. Visual grouping is navigational; asset exposure and root cause require cited evidence.

Identity source boundaries
  • Cpe dictionary1,775,266 records · observed through 2026-07-21T06:45:29.809Z27d65b0f-b718-4b4f-bb79-c47c68d09dfa
  • Cpe match643,502 records · observed through 2026-07-21T08:13:17.697Z955dae73-7302-438b-aee1-058d7cc5d48e

2 scope groups

cisco · source assertedn/an/aDirect source scope
Affected: n/a
Source-reported scope

Canonical linkage remains open; the cited source assertion is retained below.

Inspect raw assertion[{"status": "affected", "version": "n/a"}]
NVD CPE · OPERATING SYSTEMciscoios_xrVulnerable target · 19 assertions
Version 3.4; Version 3.4.0; Version 3.4.1; Version 3.4.2; Version 3.4.3; Version 3.5; Version 3.5.2; Version 3.5.3; Version 3.5.4; Version 3.6.0; Version 3.6.1; Version 3.6.2; Version 3.6.3; Version 3.7.0; Version 3.7.1; Version 3.7.2; Version 3.7.3; Version 3.8.0; Version 3.8.1Canonical identity product-a70ec7fc7d464008f2ddd19bcef52a09c444f9b0cbe4a0ab86461995673f4a82Linked exact
Scope supported
Inspect raw assertions
  1. cpe:2.3:o:cisco:ios_xr:3.4.1:*:*:*:*:*:*:*
    Official link
    Linked exact
    Role
    Vulnerable target
    Configuration
    0 · node/0 · match 2
    Logic
    OR
    Version bounds
    No explicit bounds
    Match ID
    81797938-f953-42be-b287-aa48b9860af6
  2. cpe:2.3:o:cisco:ios_xr:3.5.2:*:*:*:*:*:*:*
    Official link
    Linked exact
    Role
    Vulnerable target
    Configuration
    0 · node/0 · match 6
    Logic
    OR
    Version bounds
    No explicit bounds
    Match ID
    c5f15240-6323-4766-801a-d887f3ea8a6b
  3. cpe:2.3:o:cisco:ios_xr:3.8.0:*:*:*:*:*:*:*
    Official link
    Linked exact
    Role
    Vulnerable target
    Configuration
    0 · node/0 · match 17
    Logic
    OR
    Version bounds
    No explicit bounds
    Match ID
    96f48419-af66-4b50-acbf-9e38287a64fa
  4. cpe:2.3:o:cisco:ios_xr:3.4.2:*:*:*:*:*:*:*
    Official link
    Linked exact
    Role
    Vulnerable target
    Configuration
    0 · node/0 · match 3
    Logic
    OR
    Version bounds
    No explicit bounds
    Match ID
    92aed038-c73f-4499-b064-f01d80db0c64
  5. cpe:2.3:o:cisco:ios_xr:3.6.0:*:*:*:*:*:*:*
    Official link
    Linked exact
    Role
    Vulnerable target
    Configuration
    0 · node/0 · match 9
    Logic
    OR
    Version bounds
    No explicit bounds
    Match ID
    f497a05c-2fc5-427d-8036-2476aca956c0
  6. cpe:2.3:o:cisco:ios_xr:3.5:*:*:*:*:*:*:*
    Official link
    Linked exact
    Role
    Vulnerable target
    Configuration
    0 · node/0 · match 5
    Logic
    OR
    Version bounds
    No explicit bounds
    Match ID
    f992d03d-1db8-44c1-b59d-1c09a32a2c91
  7. cpe:2.3:o:cisco:ios_xr:3.6.3:*:*:*:*:*:*:*
    Official link
    Linked exact
    Role
    Vulnerable target
    Configuration
    0 · node/0 · match 12
    Logic
    OR
    Version bounds
    No explicit bounds
    Match ID
    46d1a634-d39c-4305-8915-4aa289fb68ee
  8. cpe:2.3:o:cisco:ios_xr:3.4:*:*:*:*:*:*:*
    Official link
    Linked exact
    Role
    Vulnerable target
    Configuration
    0 · node/0 · match 0
    Logic
    OR
    Version bounds
    No explicit bounds
    Match ID
    75538529-611a-43b5-ac4d-089c4e2e2acc
  9. cpe:2.3:o:cisco:ios_xr:3.6.1:*:*:*:*:*:*:*
    Official link
    Linked exact
    Role
    Vulnerable target
    Configuration
    0 · node/0 · match 10
    Logic
    OR
    Version bounds
    No explicit bounds
    Match ID
    2252e7b0-9112-4e9e-8cf4-4ec53c630cfd
  10. cpe:2.3:o:cisco:ios_xr:3.6.2:*:*:*:*:*:*:*
    Official link
    Linked exact
    Role
    Vulnerable target
    Configuration
    0 · node/0 · match 11
    Logic
    OR
    Version bounds
    No explicit bounds
    Match ID
    1131a524-aa7a-4c94-9ffe-54546ea7d2cc
  11. cpe:2.3:o:cisco:ios_xr:3.4.3:*:*:*:*:*:*:*
    Official link
    Linked exact
    Role
    Vulnerable target
    Configuration
    0 · node/0 · match 4
    Logic
    OR
    Version bounds
    No explicit bounds
    Match ID
    cb7a249b-af69-47d0-b6de-968b4cd0ba42
  12. cpe:2.3:o:cisco:ios_xr:3.7.0:*:*:*:*:*:*:*
    Official link
    Linked exact
    Role
    Vulnerable target
    Configuration
    0 · node/0 · match 13
    Logic
    OR
    Version bounds
    No explicit bounds
    Match ID
    21bab799-3150-46d8-aea3-9fcc73203221
  13. cpe:2.3:o:cisco:ios_xr:3.4.0:*:*:*:*:*:*:*
    Official link
    Linked exact
    Role
    Vulnerable target
    Configuration
    0 · node/0 · match 1
    Logic
    OR
    Version bounds
    No explicit bounds
    Match ID
    00da2581-f618-4f2a-ab65-da23df51af89
  14. cpe:2.3:o:cisco:ios_xr:3.8.1:*:*:*:*:*:*:*
    Official link
    Linked exact
    Role
    Vulnerable target
    Configuration
    0 · node/0 · match 18
    Logic
    OR
    Version bounds
    No explicit bounds
    Match ID
    ebb71a24-aa6c-4bad-bd37-5c191751c9df
  15. cpe:2.3:o:cisco:ios_xr:3.7.2:*:*:*:*:*:*:*
    Official link
    Linked exact
    Role
    Vulnerable target
    Configuration
    0 · node/0 · match 15
    Logic
    OR
    Version bounds
    No explicit bounds
    Match ID
    2e752aa9-cc1c-44b6-a916-a3c76a57f05c
  16. cpe:2.3:o:cisco:ios_xr:3.7.3:*:*:*:*:*:*:*
    Official link
    Linked exact
    Role
    Vulnerable target
    Configuration
    0 · node/0 · match 16
    Logic
    OR
    Version bounds
    No explicit bounds
    Match ID
    71cbe50e-9bd3-4f74-8c7a-be4905090ee2
  17. cpe:2.3:o:cisco:ios_xr:3.5.3:*:*:*:*:*:*:*
    Official link
    Linked exact
    Role
    Vulnerable target
    Configuration
    0 · node/0 · match 7
    Logic
    OR
    Version bounds
    No explicit bounds
    Match ID
    d99dc1cf-78dc-4e59-98ba-dd84702d6467
  18. cpe:2.3:o:cisco:ios_xr:3.7.1:*:*:*:*:*:*:*
    Official link
    Linked exact
    Role
    Vulnerable target
    Configuration
    0 · node/0 · match 14
    Logic
    OR
    Version bounds
    No explicit bounds
    Match ID
    99042285-94ac-4c57-8eaa-ee63c678a94a
  19. cpe:2.3:o:cisco:ios_xr:3.5.4:*:*:*:*:*:*:*
    Official link
    Linked exact
    Role
    Vulnerable target
    Configuration
    0 · node/0 · match 8
    Logic
    OR
    Version bounds
    No explicit bounds
    Match ID
    0b9fa754-e3d2-4d80-8f4b-41139973d9fc

Affected-product evidence

Accepted scope and product mapping

1 canonical links · 1 source-reported links

Mapping establishedEvidence supported

vendor-0774b265c0e837e737aaf99ed0f2450c048e61f34267ca59d8623878b839334e · product-a70ec7fc7d464008f2ddd19bcef52a09c444f9b0cbe4a0ab86461995673f4a82

Source class
Nvd cpe vulnerable target
Assertions
19
Mapping revision
cpe23-exact-mapping-v1
Observed cutoff
Aug 27, 2026
Retained assertion IDs
17a1da95-562a-432e-8503-28b7ff67a8735a3719b4-221f-4dc7-ad62-5ff8ba4da90373feb3cf-0fe9-45f5-9e76-c25838d92035794316fb-660e-4c55-abbb-1968a14e2ccb7f079ffb-d531-46f1-b2f0-329af53594568a5fc7c6-2d33-44c2-b67b-5a646917272495729f2c-6ceb-4d9c-a152-b5de3ff5a31d99c5e224-87ef-44f3-9b3d-e0fa91db4d0fa488f5a7-8798-4653-aa8f-9704c436a7f6a6ffa56b-297d-44fc-b9f7-f8488a9dffeeb57b7d38-a070-4e5d-baf3-c5c9e427a0bfb9c4a3f2-d578-47a2-82cd-97c137c180f9baafed8a-2faf-44cd-9e99-6945399fb425d10ec4bb-ce90-43e6-8ca5-4a05b40d16e7d1a50ed5-71f0-4a67-b724-3d6b1e88672fdba1ecdb-7953-499d-afce-0cca0c53595bea353c72-d330-45b5-a203-7faf6b0321aeebe26b99-014f-4c3d-ab06-6447c99e9556ee4650e8-7fdb-4b7d-b163-e74262085f03
Source-reported scopeSource-reported scope

Canonical linkage remains open; the cited source assertion is retained below.

Vendor specified only by source · Product specified only by source

Source class
Direct cve affected
Assertions
1
Mapping revision
cpe23-exact-mapping-v1
Observed cutoff
Aug 27, 2026
Retained assertion IDs
804c87b2-eb09-4384-9ddf-a80fdb7c5357

Assessments

CVSS by origin

4.3
NVDCVSS 2.0 · role Primary · priority eligiblevalid_matchAV:N/AC:M/Au:N/C:N/I:N/A:P
5.9
CVE Program sourceCVSS 3.1 · role Secondary · priority eligiblevalid_matchCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
5.9
CISA-ADPCVSS 3.1 · role unknown · display onlyDirect record assessment retained outside normalized eligibilityCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H

Direct CVE/CNA normalized decisions

5.9Priority eligible

CISA-ADP

CVSS 3.1 · Secondary · Independent enrichment · rank 2

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H
Validation
Valid match
Recomputed
5.9
Decision reason
Evidence supported
Policy
casca-direct-cvss-eligibility-v1

Assessments are retained side by side under closed precedence. Cascade never averages CVSS.

Evidence boundaries

  • KEV membership is authoritative for the catalog, not proof of exposure in any environment.
  • EPSS is a dated model probability and not an individual-environment prediction.
  • Affected or fixed status applies only to the exact cited product and version scope; remaining scope stays source-scoped.
  • NVD-carried upstream facts remain derivative; independent corroboration requires a separately authored source.
  • Only NVD metrics validated under the generation-bound calculator are Public Priority eligible; direct CVE record metrics remain display-only.
  • NVD CVSS source eligibility is closed: NVD-authored, exact record-source, or registered same-CVE container origin; unmapped sources remain display-only.
  • Core replay supports the active and immediately prior generation; retrospective valid-at replay is deferred.
  • OSV aggregation and OSV-converted NVD material are not independent corroboration.
  • Red Hat facts are vendor assertions for the exact supplied products.
  • Nonmembership and not-yet-observed states are not proof of safety.