CASCACascade Atlas

Evidence dossier

CVE-2026-7273

A stack-based buffer overflow vulnerability in the CGI program of Zyxel GS1900-48HPv2 firmware versions through 2.90(ABTQ.1)C0 could allow a LAN-based, unauthenticated attacker…

Exploited in the wild (CISA KEV since Sep 21, 2026). Zyxel reports CVSS 3.1 8.8. EPSS estimates 2.5% exploit likelihood as of Oct 22, 2026.

65.2–76.8Priority evidence range
Evidence through Oct 22, 2026, 6:07 PM UTC

As of Oct 22, 2026

Normalized restatement

A stack-based buffer overflow vulnerability in the CGI program of Zyxel GS1900-48HPv2 firmware versions through 2.90(ABTQ.1)C0 could allow a LAN-based, unauthenticated attacker to exploit the flaw and potentially execute OS commands via a crafted HTTP request.

State
PUBLISHED
Published
Jun 16, 2026
Updated
Sep 22, 2026
Evidence coverage
85%

Evidence chronology

What was known when

Download this view's receipt →
  1. Source dateFirst observed by CASCA
    CISA KEV

    Exploitation cataloged: Zyxel GS1900 Series Switches Stack-Based Buffer Overflow Vulnerability

    Inspect raw assertion
    Field
    observed_exploitation
    Value
    Zyxel GS1900 Series Switches Stack-Based Buffer Overflow Vulnerability
    Original evidence ↗
  2. 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 ↗
  3. Source dateSource date omittedFirst observed by CASCA
    Zyxel

    Record text: A stack-based buffer overflow vulnerability in the CGI program of Zyxel GS1900-48HPv2 firmware versions through 2.90(ABTQ.1)C0 could allow a LAN-based, unauthenticated attacker to exploit the flaw and potentially execute OS commands via a crafted HTTP request.

    Inspect raw assertion
    Field
    container
    Value
    A stack-based buffer overflow vulnerability in the CGI program of Zyxel GS1900-48HPv2 firmware versions through 2.90(ABTQ.1)C0 could allow a LAN-based, unauthenticated attacker to exploit the flaw and potentially execute OS commands via a crafted HTTP request.
    Original evidence ↗
  4. Source dateFirst observed by CASCA
    FIRST EPSS

    EPSS score: 2.5% probability · 84.58th percentile

    Inspect raw assertion
    Field
    model_probability
    Value
    Probability 0.025010000000; percentile 0.845820000000
    Original evidence ↗
ExploitationCatalog member

CISA KEV · catalog date Sep 21, 2026 · first observed Sep 22, 2026

Exploit likelihood2.50%

FIRST EPSS · score date Oct 22, 2026 · 84.6th percentile · first observed Oct 22, 2026

SeverityCVSS 8.8

Zyxel · CVSS 3.1 · first observed Sep 22, 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 statusLast verified source snapshot retained

The last verified source boundary remains in force for this claim.

Revision
evidence-policy-v1.1.0
Cutoff
Oct 22, 2026
Resolution
Review source contract
Exploit likelihoodEvidence supported

Eligible evidence is present for this bounded claim.

Revision
evidence-policy-v1.1.0
Cutoff
Oct 22, 2026
Resolution
None
Severity assessmentEvidence supported

Eligible evidence is present for this bounded claim.

Revision
casca-direct-cvss-eligibility-v1
Cutoff
Oct 22, 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
Oct 22, 2026
Resolution
Resolve identity

Source comparison

Who said what

CISA KEVOriginal assertion
Exploitation cataloged

Zyxel GS1900 Series Switches Stack-Based Buffer Overflow Vulnerability

Inspect raw assertion
Field
observed_exploitation
Value
Zyxel GS1900 Series Switches Stack-Based Buffer Overflow Vulnerability
Source dateFirst observed by CASCAOriginal evidence ↗
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 ↗
ZyxelOriginal assertion
Record text

A stack-based buffer overflow vulnerability in the CGI program of Zyxel GS1900-48HPv2 firmware versions through 2.90(ABTQ.1)C0 could allow a LAN-based, unauthenticated attacker to exploit the flaw and potentially execute OS commands via a crafted HTTP request.

Inspect raw assertion
Field
container
Value
A stack-based buffer overflow vulnerability in the CGI program of Zyxel GS1900-48HPv2 firmware versions through 2.90(ABTQ.1)C0 could allow a LAN-based, unauthenticated attacker to exploit the flaw and potentially execute OS commands via a crafted HTTP request.
Source dateSource date omittedFirst observed by CASCAOriginal evidence ↗
FIRST EPSSOriginal assertion
EPSS score

2.5% probability · 84.58th percentile

Inspect raw assertion
Field
model_probability
Value
Probability 0.025010000000; percentile 0.845820000000
Source dateFirst observed by CASCAOriginal evidence ↗

Applicability

Cited product scope

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

Grouped from 0 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

10 scope groups

Zyxel · source assertedZyxelGS1900-10HP firmwareDirect source scope
Affected: <= 2.90(AAZI.1)C0
Source-reported scope

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

Inspect raw assertion[{"status": "affected", "version": "<= 2.90(AAZI.1)C0"}]
Zyxel · source assertedZyxelGS1900-16 firmwareDirect source scope
Affected: <= 2.90(AAHJ.1)C0
Source-reported scope

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

Inspect raw assertion[{"status": "affected", "version": "<= 2.90(AAHJ.1)C0"}]
Zyxel · source assertedZyxelGS1900-24E firmwareDirect source scope
Affected: <= 2.90(AAHK.1)C0
Source-reported scope

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

Inspect raw assertion[{"status": "affected", "version": "<= 2.90(AAHK.1)C0"}]
Zyxel · source assertedZyxelGS1900-24EP firmwareDirect source scope
Affected: <= 2.90(ABTO.1)C0
Source-reported scope

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

Inspect raw assertion[{"status": "affected", "version": "<= 2.90(ABTO.1)C0"}]
Zyxel · source assertedZyxelGS1900-24 firmwareDirect source scope
Affected: <= 2.90(AAHL.1)C0
Source-reported scope

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

Inspect raw assertion[{"status": "affected", "version": "<= 2.90(AAHL.1)C0"}]
Zyxel · source assertedZyxelGS1900-24HPv2 firmwareDirect source scope
Affected: <= 2.90(ABTP.1)C0
Source-reported scope

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

Inspect raw assertion[{"status": "affected", "version": "<= 2.90(ABTP.1)C0"}]
Zyxel · source assertedZyxelGS1900-48 firmwareDirect source scope
Affected: <= 2.90(AAHN.1)C0
Source-reported scope

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

Inspect raw assertion[{"status": "affected", "version": "<= 2.90(AAHN.1)C0"}]
Zyxel · source assertedZyxelGS1900-48HPv2 firmwareDirect source scope
Affected: <= 2.90(ABTQ.1)C0
Source-reported scope

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

Inspect raw assertion[{"status": "affected", "version": "<= 2.90(ABTQ.1)C0"}]
Zyxel · source assertedZyxelGS1900-8 firmwareDirect source scope
Affected: <= 2.90(AAHH.1)C0
Source-reported scope

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

Inspect raw assertion[{"status": "affected", "version": "<= 2.90(AAHH.1)C0"}]
Zyxel · source assertedZyxelGS1900-8HP firmwareDirect source scope
Affected: <= 2.90(AAHI.1)C0
Source-reported scope

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

Inspect raw assertion[{"status": "affected", "version": "<= 2.90(AAHI.1)C0"}]

Affected-product evidence

Accepted scope and product mapping

0 canonical links · 2 source-reported links

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
10
Mapping revision
cpe23-exact-mapping-v1
Observed cutoff
Oct 22, 2026
Retained assertion IDs
2e179b5b-eb6b-4b19-8f3e-bf92740890024b7c68e9-6010-4dcf-a641-8c5cfdc942d074a26f5c-51ca-42b0-8c67-1c875e974c15765db4d2-5008-4d26-bc87-405e042f1eb084890f6c-6065-4a10-a306-a272b681d18e867c6b36-10d2-4ef8-b88a-f8b9c9cf40f3b7cf53ec-a053-4f53-8846-8db1d11f3ec9ce8a0caa-55b3-43a4-8d17-edf9e630310ceac74a02-b3e8-4c6f-a815-6b2b88aaa488fe9b8975-4e9e-42f5-88ab-84288e565053
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
Nvd cpe vulnerable target
Assertions
10
Mapping revision
cpe23-exact-mapping-v1
Observed cutoff
Oct 22, 2026
Retained assertion IDs
1678088c-6a12-4d9f-ae90-00111898173020a2f4e2-6d30-42a8-a6e0-f68ffc3613324ecd2670-1b31-4868-8ee6-d4cbb71b0f694f71566c-e6e3-43b2-939d-bf8616a7a0b06128f12c-6f73-4aef-ab29-5411fbe5a4da62b43b28-0d5c-4d50-b933-a1dd29c402436c4d77a2-5f75-49c5-95a0-32a68ba57cb37109f55b-aaac-4be8-bf34-9914fecea754baf031bd-f53d-4aaa-b731-349df90ae5f4df05aa38-1b8e-44aa-90cc-27b72c628ecd

Assessments

CVSS by origin

8.8
security@zyxel.com.twCVSS 3.1 · role Secondary · priority eligiblevalid_matchCVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
8.8
ZyxelCVSS 3.1 · role unknown · display onlyDirect record assessment retained outside normalized eligibilityCVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Direct CVE/CNA normalized decisions

8.8Priority eligible

Zyxel

CVSS 3.1 · Primary · Original assertion · rank 1

CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Validation
Valid match
Recomputed
8.8
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.