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CVE-2021-34730

INDEX BUILT · 2026-09-20

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Cisco Small Business RV110W, RV130, RV130W, and RV215W Routers Remote Command Execution and Denial of Service Vulnerability

CVE-2021-347304 of 4 sources documented this
46

rank 46 = 18 + 25 + 1 + 2 + 0

rank@v1 · this cycle

Someone is already using it

CISA KEV catalog · public proof-of-concept · FIRST EPSS

EPSS 0.18500  ·  without this subject the record ranks 28

What it costs you if it fires

NVD CVSS base score, then the CNA's own

CVSS 9.8, from NVD  ·  without this subject the record ranks 21

It is getting worse, not staying still

FIRST EPSS series, rescorings and bad loads removed

rose on 2026-09-14  ·  without this subject the record ranks 45

How much of the world it touches

NVD CPE configurations

1 product in the CPE ranges  ·  without this subject the record ranks 44

Someone else already set the date

CISA KEV remediation due date

no CISA due date  ·  without this subject the record ranks 46

Unaudited dollar value2 of 3 inputs carry a receipt
Exposure$923,000over the next 30 days, if this record is yours
Movement-$709,000on 2022-04-01, the last material move, 4 years, 5 months before this reading
Basisassumeda published average, not your estate

$923,000 = $4.99M incident cost x 1 exposure x 0.185 likelihood

udv@v1 · unaudited · wrong for you until you say what you run

$4.99M is the cost of a breach that happened, from IBM Cost of a Data Breach Report 2026, global average. It is not the value of any asset of yours. That average already covers breaches of every severity, so scaling it by exposure understates a partial-impact record. That is an assumption, not a measurement. Your own asset value goes in the decision record.

Hindsight · the state

0.185EPSSNOT IN KEVas of 2026-09-20
Severity9.8 CRITICALreceipt
Harmtotal loss · unauthenticatedreceipt
Exploitationpublic proof-of-conceptreceipt
Defenseno fix version held
Movementrisenreceipt
PLATEAU10Minimal movement since 2026-04-30, 137 days at 0.18, as of 2026-09-14. arc-rules@v1

Foresight · where to check next

SonicWall SMA100Fortinet FortiNDRCisco SmallQUALITIA CO.,F5 BIG-IP34730

This record is one instance of CWE-121, stack-based buffer overflow. The index holds 3820 prior instances of this class, 19 KEV-listed. The nearest of its KEV-listed records are drawn beside this. taxonomy@v1

Full pattern panel

Prior records in this weakness class. Each is its own record, dated and receipted.
Color is a claim, not decoration:the hostile worldthe defenseno signalspoke length is how much of the record matches, not how bad it is

Running Cisco Small Business RV Series Router…? Check your version

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Harm, if it fires from the vector and the weakness

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Reachnetwork-reachable · no privileges required · no user interaction · low attack complexityreceipt
ImpactComplete confidentiality, integrity and availability lossreceipt
Scored fromCVSS v3.1 · the CNA's vectorreceipt
Weakness classCWE-121 Stack-based Buffer Overflowreceipt
Published consequencesCWE-121: Availability: Modify Memory, DoS: Crash, Exit, or Restart, DoS: Resource Consumption (CPU), DoS: Resource Consumption (Memory)…[email protected]

CISA KEV & Federal Remediation Deadline from the record and CISA

The fix, and how long it's been waiting.

Fixed inNo fix version in held sources, as the index stood on 14 Sep 2026.
Patch available sinceNo dated patch-availability record in held sources. The index holds reference URLs without dates and only the current revision of the CVE record, so the day a fix first existed cannot be derived. Only the versions it landed in.

Exploit Status & Known PoCs a ladder, not a score

Current rung: Proof-of-concept published · 1 public repository, 2021-09-30.

  • RUNG 1Nothing observed in held sources
  • RUNG 2Proof-of-concept published · 1 public repository2021-09-30receipt
  • RUNG 3Exploited in the wild · CISA KEV listed
  • RUNG 4Ransomware campaign use known

Authority who says so

CVSS, the CNA9.8 CRITICALreceipt
CVSS, NVD9.8 CRITICALreceipt
Exploit probability0.185 · top 3% of all CVEsreceipt
Blast breadth1 product across 1 vendorderived
Assigned byciscoreceipt
Recorded changes35 · last 19 Sep 2026derived

Affected & Fixed Versions as published

Affected productCisco Small Business RV Series Router Firmwarereceipt
Published rangescisco application extension platform 1.0.3.55receipt

A rung lights from a row in the index, never from an assessment. "Held sources" is the true scope of the claim: this index reads the CVE record, NVD, CISA KEV, FIRST's EPSS and public proof-of-concept repositories, and it does not observe attacks.

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Attack path

Unauthenticated network requestno credentials, no interactionCisco Small Business RV Series Rout…CWE-121 weaknessFull compromise (C/I/A)C:H / I:H / A:Hexploits CWE-121data compromise

What it is stated by the CNA

A vulnerability in the Universal Plug-and-Play (UPnP) service of Cisco Small Business RV110W, RV130, RV130W, and RV215W Routers could allow an unauthenticated, remote attacker to execute arbitrary code or cause an affected device to restart unexpectedly, resulting in a denial of service (DoS) condition. This vulnerability is due to improper validation of incoming UPnP traffic. An attacker could exploit this vulnerability by sending a crafted UPnP request to an affected device. A successful exploit could allow the attacker to execute arbitrary code as the root user on the underlying operating system or cause the device to reload, resulting in a DoS condition. receipt

Read the rest of the CNA's description

Cisco has not released software updates that address this vulnerability.

NVD's analysis a second authority

severity
9.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
weakness
CWE-121; CWE-787
affected versions
cisco application extension platform 1.0.3.55
also scored by
[email protected] 9.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

check it yourself tools.cisco.com receipt

Dated events

2022-02-04EPSS moved 0.05 to 0.152025-03-17EPSS moved 0.01 to 0.242026-06-15EPSS moved 0.26 to 0.14

Movement the material steps

19 Aug 20210.01142
4 Feb 20220.15362 · crossed 0.10
1 Apr 20220.01156 · crossed 0.10
7 Mar 20230.00282 · scoring model v2023.03.01
17 Mar 20250.24127 · crossed 0.10 · scoring model v2025.03.14
19 Mar 20250.45579
31 Aug 20250.31798
15 Jun 20260.13578 · scoring model v2026.06.15
14 Sep 20260.185
Show all 32 observations
19 Aug 20210.01142
1 Oct 20210.04927
11 Oct 20210.01142
6 Jan 20220.04927
4 Feb 20220.15362
1 Apr 20220.01156
7 Mar 20230.00282
11 Mar 20230.00299
26 Mar 20230.00312
3 Aug 20230.00327
10 Nov 20230.00486
24 Mar 20240.00503
3 May 20240.00537
24 Jul 20240.00567
17 Mar 20250.24127
19 Mar 20250.45579
20 Mar 20250.35783
27 Mar 20250.45579
28 Mar 20250.35783
29 Mar 20250.45579
30 Mar 20250.35783
31 Aug 20250.31798
9 Sep 20250.31049
11 Sep 20250.37268
18 Nov 20250.25279
21 Nov 20250.37268
30 Apr 20260.26456
5 May 20260.26348
15 Jun 20260.13578
20 Aug 20260.13941
8 Sep 20260.13831
14 Sep 20260.185

32 observations held. A highlighted step crossed a promotion threshold. A step marked with a scoring model moved because the instrument was replaced, not because the vulnerability changed. receipt

The full biography

EPSS 0.185Published2021-08-18Public PoC2021-09-30Index as of2026-09-14

The record had been public for 5 years when this index was last written.

Published 2021-08-18 receipt · Public PoC 2021-09-30 receipt · Index as of 2026-09-14 derived

The pattern, elsewhere

This record is one instance of CWE-121, stack-based buffer overflow. The index holds 3820 prior instances of this class, 19 KEV-listed. The nearest of its KEV-listed records are drawn beside this. [email protected]

CVE-2021-20038 · SonicWall SMA100matches 9 of 10KEV listed · 2021receipt
CVE-2025-32756 · Fortinet FortiNDRmatches 9 of 10KEV listed · 2025receipt
CVE-2022-20700 · Cisco Small Business RV Series Router Firmwarematches 9 of 10KEV listed · 2022receipt
CVE-2022-20701 · Cisco Small Business RV Series Router Firmwarematches 9 of 10KEV listed · 2022receipt
CVE-2025-42599 · QUALITIA CO., LTD. Active! mail 6matches 8 of 10KEV listed · 2025receipt
CVE-2025-53521 · F5 BIG-IPmatches 8 of 10KEV listed · 2025receipt

"Matches n of m" counts the attributes the two records can both be compared on: the CVSS metrics they share a version of, any weakness class beyond this one, and the vendor. fit-rules@v1

3820 records in this class held. The six above are drawn from the ones CISA has listed as exploited, ranked by how much of the record matches this one. That is why every one of them is KEV-listed: the pool is, so the colour on those spokes says nothing the pool has not already said.

No curated product neighbourhood is held for this product, so the records above are the nearest this index can name. The neighbourhood table covers a small set of products and is extended by hand.

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