CVE-2021-27853

🗓️ 27 Sep 2022 17:55:09Reported by certccType

cve🔗 web.nvd.nist.gov📰️ 3 Media mentions👁 120 Views

CVE-2021-27853: Bypass Layer 2 network filters with VLAN 0 and LLC/SNAP header

Reporter	Title	Published	Views	Family All 18
Arista	Security Advisory 0080	27 Sep 202200:00	–	arista
BDU FSTEC	The vulnerability of the Ethernet encapsulation protocol lies in its ability to combine headers, which allows attackers to trigger a service failure or execute a Middleware Interception Attack (MITM).	28 Sep 202200:00	–	bdu_fstec
Circl	CVE-2021-27853	27 Sep 202222:28	–	circl
Cisco	Vulnerabilities in Layer 2 Network Security Controls Affecting Cisco Products: September 2022	27 Sep 202216:00	–	cisco
CNNVD	多款Cisco产品安全漏洞	27 Sep 202200:00	–	cnnvd
Cvelist	CVE-2021-27853 L2 network filtering can be bypassed using stacked VLAN0 and LLC/SNAP headers	27 Sep 202217:55	–	cvelist
EUVD	EUVD-2021-14591	7 Oct 202500:30	–	euvd
F5 Networks	K45012151: Layer 2 security bypass issue CVE-2021-27861, CVE-2021-27862, CVE-2021-27853, CVE-2021-27854	21 Feb 202318:54	–	f5
Ivanti	SA45654 - Multiple OpenSSL Vulnerabilities in Layer 2 network filtering capabilities	14 Feb 202307:22	–	ivanti
NCSC	Researcher discovered vulnerabilities in Layer-2 managed switches	28 Sep 202200:00	–	ncsc

NVD

Node

ieee ieee_802.2Range≤802.2h-1997

Node

ietf p802.1qRange≤d1.0

Node

AND

cisco catalyst_6503-e_firmwareMatch15.5(01.01.85)sy07

cisco catalyst_6503-eMatch-

Node

AND

cisco catalyst_6504-e_firmwareMatch15.5(01.01.85)sy07

cisco catalyst_6504-eMatch-

Node

AND

cisco catalyst_6506-e_firmwareMatch15.5(01.01.85)sy07

cisco catalyst_6506-eMatch-

Node

AND

cisco catalyst_6509-e_firmwareMatch15.5(01.01.85)sy07

cisco catalyst_6509-eMatch-

Node

AND

cisco catalyst_6509-neb-a_firmwareMatch15.5(01.01.85)sy07

cisco catalyst_6509-neb-aMatch-

Node

AND

cisco catalyst_6509-v-e_firmwareMatch15.5(01.01.85)sy07

cisco catalyst_6509-v-eMatch-

Node

AND

cisco catalyst_6513-e_firmwareMatch15.5(01.01.85)sy07

cisco catalyst_6513-eMatch-

Node

AND

cisco catalyst_6807-xl_firmwareMatch15.5(01.01.85)sy07

cisco catalyst_6807-xlMatch-

Node

AND

cisco catalyst_6840-x_firmwareMatch15.5(01.01.85)sy07

cisco catalyst_6840-xMatch-

Node

AND

cisco catalyst_6880-x_firmwareMatch15.5(01.01.85)sy07

cisco catalyst_6880-xMatch-

Node

AND

cisco catalyst_c6816-x-le_firmwareMatch15.5(01.01.85)sy07

cisco catalyst_c6816-x-leMatch-

Node

AND

cisco catalyst_c6824-x-le-40g_firmwareMatch15.5(01.01.85)sy07

cisco catalyst_c6824-x-le-40gMatch-

Node

AND

cisco catalyst_c6832-x-le_firmwareMatch15.5(01.01.85)sy07

cisco catalyst_c6832-x-leMatch-

Node

AND

cisco catalyst_c6840-x-le-40g_firmwareMatch15.5(01.01.85)sy07

cisco catalyst_c6840-x-le-40gMatch-

Node

AND

cisco catalyst_6800ia_firmwareMatch15.5(01.01.85)sy07

cisco catalyst_6800iaMatch-

Node

AND

cisco ios_xeMatch17.3.3

cisco ios_xeMatch15.2(07)e02

cisco ios_xeMatch15.2(07)e03

cisco ios_xeMatch17.4.1

cisco ios_xeMatch17.6.1

cisco catalyst_3650-12x48fd-eMatch-

cisco catalyst_3650-12x48fd-lMatch-

cisco catalyst_3650-12x48fd-sMatch-

cisco catalyst_3650-12x48uq-eMatch-

cisco catalyst_3650-12x48uq-lMatch-

cisco catalyst_3650-12x48uq-sMatch-

cisco catalyst_3650-12x48ur-eMatch-

cisco catalyst_3650-12x48ur-lMatch-

cisco catalyst_3650-12x48ur-sMatch-

cisco catalyst_3650-12x48uz-eMatch-

cisco catalyst_3650-12x48uz-lMatch-

cisco catalyst_3650-12x48uz-sMatch-

cisco catalyst_3650-24pd-eMatch-

cisco catalyst_3650-24pd-lMatch-

cisco catalyst_3650-24pd-sMatch-

cisco catalyst_3650-24pdm-eMatch-

cisco catalyst_3650-24pdm-lMatch-

cisco catalyst_3650-24pdm-sMatch-

cisco catalyst_3650-24ps-eMatch-

cisco catalyst_3650-24ps-lMatch-

cisco catalyst_3650-24ps-sMatch-

cisco catalyst_3650-24td-eMatch-

cisco catalyst_3650-24td-lMatch-

cisco catalyst_3650-24td-sMatch-

cisco catalyst_3650-24ts-eMatch-

cisco catalyst_3650-24ts-lMatch-

cisco catalyst_3650-24ts-sMatch-

cisco catalyst_3650-48fd-eMatch-

cisco catalyst_3650-48fd-lMatch-

cisco catalyst_3650-48fd-sMatch-

cisco catalyst_3650-48fq-eMatch-

cisco catalyst_3650-48fq-lMatch-

cisco catalyst_3650-48fq-sMatch-

cisco catalyst_3650-48fqm-eMatch-

cisco catalyst_3650-48fqm-lMatch-

cisco catalyst_3650-48fqm-sMatch-

cisco catalyst_3650-48fs-eMatch-

cisco catalyst_3650-48fs-lMatch-

cisco catalyst_3650-48fs-sMatch-

cisco catalyst_3650-48pd-eMatch-

cisco catalyst_3650-48pd-lMatch-

cisco catalyst_3650-48pd-sMatch-

cisco catalyst_3650-48pq-eMatch-

cisco catalyst_3650-48pq-lMatch-

cisco catalyst_3650-48pq-sMatch-

cisco catalyst_3650-48ps-eMatch-

cisco catalyst_3650-48ps-lMatch-

cisco catalyst_3650-48ps-sMatch-

cisco catalyst_3650-48td-eMatch-

cisco catalyst_3650-48td-lMatch-

cisco catalyst_3650-48td-sMatch-

cisco catalyst_3650-48tq-eMatch-

cisco catalyst_3650-48tq-lMatch-

cisco catalyst_3650-48tq-sMatch-

cisco catalyst_3650-48ts-eMatch-

cisco catalyst_3650-48ts-lMatch-

cisco catalyst_3650-48ts-sMatch-

cisco catalyst_3650-8x24pd-eMatch-

cisco catalyst_3650-8x24pd-lMatch-

cisco catalyst_3650-8x24pd-sMatch-

cisco catalyst_3650-8x24uq-eMatch-

cisco catalyst_3650-8x24uq-lMatch-

cisco catalyst_3650-8x24uq-sMatch-

cisco catalyst_3850-12s-eMatch-

cisco catalyst_3850-12s-sMatch-

cisco catalyst_3850-12xs-eMatch-

cisco catalyst_3850-12xs-sMatch-

cisco catalyst_3850-16xs-eMatch-

cisco catalyst_3850-16xs-sMatch-

cisco catalyst_3850-24p-eMatch-

cisco catalyst_3850-24p-lMatch-

cisco catalyst_3850-24pw-sMatch-

cisco catalyst_3850-24s-eMatch-

cisco catalyst_3850-24s-sMatch-

cisco catalyst_3850-24t-eMatch-

cisco catalyst_3850-24t-lMatch-

cisco catalyst_3850-24t-sMatch-

cisco catalyst_3850-24u-eMatch-

cisco catalyst_3850-24u-lMatch-

cisco catalyst_3850-24u-sMatch-

cisco catalyst_3850-24xs-eMatch-

cisco catalyst_3850-24xs-sMatch-

cisco catalyst_3850-24xu-eMatch-

cisco catalyst_3850-24xu-lMatch-

cisco catalyst_3850-24xu-sMatch-

cisco catalyst_3850-32xs-eMatch-

cisco catalyst_3850-32xs-sMatch-

cisco catalyst_3850-48f-eMatch-

cisco catalyst_3850-48f-lMatch-

cisco catalyst_3850-48f-sMatch-

cisco catalyst_3850-48p-eMatch-

cisco catalyst_3850-48p-lMatch-

cisco catalyst_3850-48p-sMatch-

cisco catalyst_3850-48pw-sMatch-

cisco catalyst_3850-48t-eMatch-

cisco catalyst_3850-48t-lMatch-

cisco catalyst_3850-48t-sMatch-

cisco catalyst_3850-48u-eMatch-

cisco catalyst_3850-48u-lMatch-

cisco catalyst_3850-48u-sMatch-

cisco catalyst_3850-48xs-eMatch-

cisco catalyst_3850-48xs-f-eMatch-

cisco catalyst_3850-48xs-f-sMatch-

cisco catalyst_3850-48xs-sMatch-

cisco catalyst_9200Match-

cisco catalyst_9200cxMatch-

cisco catalyst_9200lMatch-

cisco catalyst_9300Match-

cisco catalyst_9300lMatch-

cisco catalyst_9300lmMatch-

cisco catalyst_9300xMatch-

cisco catalyst_9400Match-

cisco catalyst_9500Match-

cisco catalyst_9500hMatch-

cisco catalyst_9600Match-

cisco catalyst_9600xMatch-

cisco catalyst_c3850-12x48u-eMatch-

cisco catalyst_c3850-12x48u-lMatch-

cisco catalyst_c3850-12x48u-sMatch-

Node

AND

cisco meraki_ms390_firmwareMatch-

cisco meraki_ms390Match-

Node

AND

cisco meraki_ms210_firmwareMatch-

cisco meraki_ms210Match-

Node

AND

cisco meraki_ms225_firmwareMatch-

cisco meraki_ms225Match-

Node

AND

cisco meraki_ms250_firmwareMatch-

cisco meraki_ms250Match-

Node

AND

cisco meraki_ms350_firmwareMatch-

cisco meraki_ms350Match-

Node

AND

cisco meraki_ms355_firmwareMatch-

cisco meraki_ms355Match-

Node

AND

cisco meraki_ms410_firmwareMatch-

cisco meraki_ms410Match-

Node

AND

cisco meraki_ms420_firmwareMatch-

cisco meraki_ms420Match-

Node

AND

cisco meraki_ms425_firmwareMatch-

cisco meraki_ms425Match-

Node

AND

cisco meraki_ms450_firmwareMatch-

cisco meraki_ms450Match-

Node

AND

cisco nexus_93180yc-ex_firmwareMatch9.3(5)

cisco nexus_93180yc-exMatch-

Node

AND

cisco nexus_93180yc-fx_firmwareMatch9.3(5)

cisco nexus_93180yc-fxMatch-

Node

AND

cisco nexus_93180yc-fx3_firmwareMatch9.3(5)

cisco nexus_93180yc-fx3Match-

Node

AND

cisco nexus_93240yc-fx2_firmwareMatch9.3(5)

cisco nexus_93240yc-fx2Match-

Node

AND

cisco nexus_93360yc-fx2_firmwareMatch9.3(5)

cisco nexus_93360yc-fx2Match-

Node

AND

cisco nexus_93120tx_firmwareMatch9.3(5)

cisco nexus_93120txMatch-

Node

AND

cisco nexus_93108tc-ex_firmwareMatch9.3(5)

cisco nexus_93108tc-exMatch-

Node

AND

cisco nexus_9348gc-fxp_firmwareMatch9.3(5)

cisco nexus_9348gc-fxpMatch-

Node

AND

cisco nexus_93108tc-fx_firmwareMatch9.3(5)

cisco nexus_93108tc-fxMatch-

Node

AND

cisco nexus_93108tc-fx3p_firmwareMatch9.3(5)

cisco nexus_93108tc-fx3pMatch-

Node

AND

cisco nexus_93216tc-fx2_firmwareMatch9.3(5)

cisco nexus_93216tc-fx2Match-

Node

AND

cisco n9k-c9316d-gx_firmwareMatch9.3(5)

cisco n9k-c9316d-gxMatch-

Node

AND

cisco n9k-c93600cd-gx_firmwareMatch9.3(5)

cisco n9k-c93600cd-gxMatch-

Node

AND

cisco n9k-c9332d-gx2b_firmwareMatch9.3(5)

cisco n9k-c9332d-gx2bMatch-

Node

AND

cisco n9k-c9348d-gx2a_firmwareMatch9.3(5)

cisco n9k-c9348d-gx2aMatch-

Node

AND

cisco n9k-c9364d-gx2a_firmwareMatch9.3(5)

cisco n9k-c9364d-gx2aMatch-

Node

AND

cisco n9k-x97160yc-ex_firmwareMatch9.3(5)

cisco n9k-x97160yc-exMatch-

Node

AND

cisco n9k-x9788tc-fx_firmwareMatch9.3(5)

cisco n9k-x9788tc-fxMatch-

Node

AND

cisco n9k-x9564px_firmwareMatch9.3(5)

cisco n9k-x9564pxMatch-

Node

AND

cisco n9k-x9464px_firmwareMatch9.3(5)

cisco n9k-x9464pxMatch-

Node

AND

cisco n9k-x9564tx_firmwareMatch9.3(5)

cisco n9k-x9564txMatch-

Node

AND

cisco n9k-x9464tx2_firmwareMatch9.3(5)

cisco n9k-x9464tx2Match-

Node

AND

cisco nexus_9636pq_firmwareMatch9.3(5)

cisco nexus_9636pqMatch-

Node

AND

cisco nexus_x9636q-r_firmwareMatch9.3(5)

cisco nexus_x9636q-rMatch-

Node

AND

cisco nexus_9536pq_firmwareMatch9.3(5)

cisco nexus_9536pqMatch-

Node

AND

cisco nexus_9432pq_firmwareMatch9.3(5)

cisco nexus_9432pqMatch-

Node

AND

cisco nexus_9736pq_firmwareMatch9.3(5)

cisco nexus_9736pqMatch-

Node

AND

cisco n9k-x9736c-fx_firmwareMatch9.3(5)

cisco n9k-x9736c-fxMatch-

Node

AND

cisco n9k-x9732c-ex_firmwareMatch9.3(5)

cisco n9k-x9732c-exMatch-

Node

AND

cisco n9k-x9732c-fx_firmwareMatch9.3(5)

cisco n9k-x9732c-fxMatch-

Node

AND

cisco n9k-x9736c-ex_firmwareMatch9.3(5)

cisco n9k-x9736c-exMatch-

Node

AND

cisco n9k-x9636c-rx_firmwareMatch9.3(5)

cisco n9k-x9636c-rxMatch-

Node

AND

cisco n9k-x9636c-r_firmwareMatch9.3(5)

cisco n9k-x9636c-rMatch-

Node

AND

cisco n9k-x9432c-s_firmwareMatch9.3(5)

cisco n9k-x9432c-sMatch-

Node

AND

cisco nexus_9716d-gx_firmwareMatch9.3(5)

cisco nexus_9716d-gxMatch-

Node

AND

cisco nexus_9504_firmwareMatch9.3(5)

cisco nexus_9504Match-

Node

AND

cisco nexus_9508_firmwareMatch9.3(5)

cisco nexus_9508Match-

Node

AND

cisco nexus_9516_firmwareMatch9.3(5)

cisco nexus_9516Match-

Node

AND

cisco nexus_92160yc-x_firmwareMatch9.3(5)

cisco nexus_92160yc-xMatch-

Node

AND

cisco nexus_9272q_firmwareMatch9.3(5)

cisco nexus_9272qMatch-

Node

AND

cisco nexus_92304qc_firmwareMatch9.3(5)

cisco nexus_92304qcMatch-

Node

AND

cisco nexus_9236c_firmwareMatch9.3(5)

cisco nexus_9236cMatch-

Node

AND

cisco nexus_92300yc_firmwareMatch9.3(5)

cisco nexus_92300ycMatch-

Node

AND

cisco nexus_92348gc-x_firmwareMatch9.3(5)

cisco nexus_92348gc-xMatch-

Node

AND

cisco nexus_9364c_firmwareMatch9.3(5)

cisco nexus_9364cMatch-

Node

AND

cisco nexus_9336c-fx2_firmwareMatch9.3(5)

cisco nexus_9336c-fx2Match-

Node

AND

cisco nexus_9336c-fx2-e_firmwareMatch9.3(5)

cisco nexus_9336c-fx2-eMatch-

Node

AND

cisco nexus_9332c_firmwareMatch9.3(5)

cisco nexus_9332cMatch-

Node

AND

cisco nexus_9364c-gx_firmwareMatch9.3(5)

cisco nexus_9364c-gxMatch-

Node

AND

cisco nexus_9800_firmwareMatch9.3(5)

cisco nexus_9800Match-

Node

AND

cisco sf500-24_firmwareMatch3.0.0.61

cisco sf500-24Match-

Node

AND

cisco sf-500-24mp_firmwareMatch3.0.0.61

cisco sf-500-24mpMatch-

Node

AND

cisco sf500-24p_firmwareMatch3.0.0.61

cisco sf500-24pMatch-

Node

AND

cisco sf500-48_firmwareMatch3.0.0.61

cisco sf500-48Match-

Node

AND

cisco sf500-48mp_firmwareMatch3.0.0.61

cisco sf500-48mpMatch-

Node

AND

cisco sf500-18p_firmwareMatch3.0.0.61

cisco sf500-18pMatch-

Node

AND

cisco sg500-28_firmwareMatch3.0.0.61

cisco sg500-28Match-

Node

AND

cisco sg500-28mpp_firmwareMatch3.0.0.61

cisco sg500-28mppMatch-

Node

AND

cisco sg500-28p_firmwareMatch3.0.0.61

cisco sg500-28pMatch-

Node

AND

cisco sg500-52_firmwareMatch3.0.0.61

cisco sg500-52Match-

Node

AND

cisco sg500-52mp_firmwareMatch3.0.0.61

cisco sg500-52mpMatch-

Node

AND

cisco sg500-52p_firmwareMatch3.0.0.61

cisco sg500-52pMatch-

Node

AND

cisco sg500x-24_firmwareMatch3.0.0.61

cisco sg500x-24Match-

Node

AND

cisco sg500x-24mpp_firmwareMatch3.0.0.61

cisco sg500x-24mppMatch-

Node

AND

cisco sg500x-24p_firmwareMatch3.0.0.61

cisco sg500x-24pMatch-

Node

AND

cisco sg500x-48_firmwareMatch3.0.0.61

cisco sg500x-48Match-

Node

AND

cisco sg500x-48mpp_firmwareMatch3.0.0.61

cisco sg500x-48mppMatch-

Node

AND

cisco sg500x-48p_firmwareMatch3.0.0.61

cisco sg500x-48pMatch-

[
  {
    "vendor": "IEEE",
    "product": "802.2",
    "versions": [
      {
        "version": "802.2h-1997",
        "status": "affected",
        "lessThanOrEqual": "802.2h-1997",
        "versionType": "custom"
      }
    ]
  },
  {
    "vendor": "IETF",
    "product": "draft-ietf-v6ops-ra-guard",
    "versions": [
      {
        "version": "08",
        "status": "affected",
        "lessThanOrEqual": "08",
        "versionType": "custom"
      }
    ]
  },
  {
    "vendor": "IETF",
    "product": "P802.1Q",
    "versions": [
      {
        "version": "D1.0",
        "status": "affected",
        "lessThanOrEqual": "D1.0",
        "versionType": "custom"
      }
    ]
  }
]

Source	Link
blog	www.blog.champtar.fr/VLAN0_LLC_SNAP/
kb	www.kb.cert.org/vuls/id/855201
tools	www.tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-VU855201-J3z8CKTX
datatracker	www.datatracker.ietf.org/doc/draft-ietf-v6ops-ra-guard/08/
standards	www.standards.ieee.org/ieee/802.2/1048/
standards	www.standards.ieee.org/ieee/802.1Q/10323/
kb	www.kb.cert.org/vuls/id/855201

17 Jun 2026 03:45Current

4.7Medium risk

Vulners AI Score4.7

CVSS 3.14.7

EPSS0.0071

SSVC

CWE-290