Exploitation evidence
Known exploited · CISA KEV listed
Added 2021-11-03. Ransomware campaign use: Unknown.
CISA required action: Apply updates per vendor instructions.
CISA due date: 2021-11-17. This is the catalog’s deadline, not an assessment of your organization’s exposure.
KEV checked 13 Nov 2026, 00:20 Jerusalem · Original catalog ↗Reported products and versions
n/a / Buffalo WSR-2533DHPL2, Buffalo WSR-2533DHP3
Default status: Not specified
- affected: WSR-2533DHPL2 <=1.02, WSR-2533DHP3 <= 1.24
Fixes and workarounds
No explicit solution text in the downloaded CVE record. Consult the vendor advisory; unaffected version ranges are shown above as reported, not inferred as a patch recommendation.
Sources and related reporting
Observed change timeline
History begins when Egret first downloads each source. It is not the complete upstream CVE history.
12 Nov 2026, 18:20 Jerusalem · EPSS observation updated
Stored EPSS snapshot at this observation.
{
"date": "2026-11-12",
"epss": 0.99982,
"percentile": 0.99982
}10 Nov 2026, 18:20 Jerusalem · EPSS observation updated
Stored EPSS snapshot at this observation.
{
"date": "2026-11-10",
"epss": 0.99982,
"percentile": 0.99982
}09 Nov 2026, 18:20 Jerusalem · EPSS observation updated
Stored EPSS snapshot at this observation.
{
"date": "2026-11-09",
"epss": 0.99982,
"percentile": 0.99982
}08 Nov 2026, 18:20 Jerusalem · EPSS observation updated
Stored EPSS snapshot at this observation.
{
"date": "2026-11-08",
"epss": 0.99982,
"percentile": 0.99982
}07 Nov 2026, 18:20 Jerusalem · EPSS observation updated
Stored EPSS snapshot at this observation.
{
"date": "2026-11-07",
"epss": 0.99982,
"percentile": 0.99982
}06 Nov 2026, 18:20 Jerusalem · EPSS observation updated
Stored EPSS snapshot at this observation.
{
"date": "2026-11-06",
"epss": 0.99982,
"percentile": 0.99982
}06 Nov 2026, 06:20 Jerusalem · EPSS observation updated
Stored EPSS snapshot at this observation.
{
"date": "2026-11-05",
"epss": 0.99982,
"percentile": 0.99982
}06 Nov 2026, 00:20 Jerusalem · CVE Program record changed
Stored CNA snapshot at this observation.
{
"containers": {
"adp": [
{
"providerMetadata": {
"dateUpdated": "2024-08-03T17:30:07.572Z",
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},
{
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"third-party-advisory",
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"url": "https://www.kb.cert.org/vuls/id/914124"
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{
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"url": "https://www.secpod.com/blog/arcadyan-based-routers-and-modems-under-active-exploitation/"
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{
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"confidentialityImpact": "HIGH",
"integrityImpact": "HIGH",
"privilegesRequired": "NONE",
"scope": "UNCHANGED",
"userInteraction": "NONE",
"vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
"version": "3.1"
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{
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{
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{
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"timestamp": "2025-02-06T20:25:22.891349Z",
"version": "2.0.3"
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"time": "2021-11-03T00:00:00.000Z",
"value": "CVE-2021-20090 added to CISA KEV"
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"title": "CISA ADP Vulnrichment"
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],
"cna": {
"affected": [
{
"product": "Buffalo WSR-2533DHPL2, Buffalo WSR-2533DHP3",
"vendor": "n/a",
"versions": [
{
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"version": "WSR-2533DHPL2 <=1.02, WSR-2533DHP3 <= 1.24"
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]
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"descriptions": [
{
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"value": "A path traversal vulnerability in the web interfaces of Buffalo WSR-2533DHPL2 firmware version <= 1.02 and WSR-2533DHP3 firmware version <= 1.24 could allow unauthenticated remote attackers to bypass authentication."
}
],
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},
{
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},
"cveMetadata": {
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"datePublished": "2021-04-29T00:00:00.000Z",
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}04 Nov 2026, 18:20 Jerusalem · EPSS observation updated
Stored EPSS snapshot at this observation.
{
"date": "2026-11-04",
"epss": 0.99982,
"percentile": 0.99982
}03 Nov 2026, 18:20 Jerusalem · EPSS observation updated
Stored EPSS snapshot at this observation.
{
"date": "2026-11-03",
"epss": 0.99982,
"percentile": 0.99982
}03 Nov 2026, 02:22 Jerusalem · EPSS observation updated
Stored EPSS snapshot at this observation.
{
"date": "2026-11-02",
"epss": 0.99982,
"percentile": 0.99982
}03 Nov 2026, 02:22 Jerusalem · CISA KEV status changed
Stored KEV snapshot at this observation.
{
"cveID": "CVE-2021-20090",
"cwes": [
"CWE-22"
],
"dateAdded": "2021-11-03",
"dueDate": "2021-11-17",
"forensicTriage": "No",
"knownRansomwareCampaignUse": "Unknown",
"notes": "https://nvd.nist.gov/vuln/detail/CVE-2021-20090",
"product": "Buffalo Firmware",
"requiredAction": "Apply updates per vendor instructions.",
"shortDescription": "Arcadyan Buffalo firmware contains a path traversal vulnerability that could allow unauthenticated, remote attackers to bypass authentication and access sensitive information. This vulnerability affects multiple routers across several different vendors.",
"vendorProject": "Arcadyan",
"vulnerabilityName": "Arcadyan Buffalo Firmware Path Traversal Vulnerability"
}