CVE Intelligence
CISA KEV High

CVE-2018-0155 — Cisco Catalyst Bidirectional Forwarding Detection Denial-of-Service Vulnerability

A vulnerability in the Bidirectional Forwarding Detection (BFD) offload implementation of Cisco Catalyst 4500 Series Switches and Cisco Catalyst 4500-X Series Switches could allow an unauthenticated, remote attacker to cause a crash of the iosd process, causing a denial of service (DoS) condition. The vulnerability is due to insufficient error handling when the BFD header in a BFD packet is incomplete. An attacker could exploit this vulnerability by sending a crafted BFD message to or across an affected switch. A successful exploit could allow the attacker to trigger a reload of the system. This vulnerability affects Catalyst 4500 Supervisor Engine 6-E (K5), Catalyst 4500 Supervisor Engine 6L-E (K10), Catalyst 4500 Supervisor Engine 7-E (K10), Catalyst 4500 Supervisor Engine 7L-E (K10), Catalyst 4500E Supervisor Engine 8-E (K10), Catalyst 4500E Supervisor Engine 8L-E (K10), Catalyst 4500E Supervisor Engine 9-E (K10), Catalyst 4500-X Series Switches (K10), Catalyst 4900M Switch (K5), Catalyst 4948E Ethernet Switch (K5). Cisco Bug IDs: CSCvc40729.

Published Mar 28, 2018 · Updated Oct 13, 2026 · Sources: CISA Known Exploited Vulnerabilities, NIST National Vulnerability Database, CVE Program (cve.org) e CISA ADP, GitHub Security Advisories · CNA: cisco

Who exploits it and how urgent it is

A 0–100 score combining confirmed exploitation, ransomware and APT use, public exploits, EPSS and severity.

CISA KEV · Mar 3, 2022
How the score was calculated
  • Confirmed exploitation (CISA KEV)+35
  • EPSS 7.7% (30-day exploitation probability)+14
  • Technical severity (high)+6
  • Automatable exploitation (SSVC)+3

The score orders the patch queue; it does not replace your asset context (internet exposure, criticality, compensating controls).

Triage

Is it exploited, how likely is exploitation, what does it touch, and how severe do the sources call it.

Exploitation
Confirmed
CISA KEV, listed Mar 3, 2022
EPSS FIRST
7.74%
ahead of 95% of scored CVEs · Oct 14, 2026
Affects
Cisco
Ios and 1 more
CVSS base
8.6
High · 4 source(s)

CISA SSVC assessment CISA

Three decision points CISA publishes for the CVEs it assesses (SSVC 2.0.3). A stakeholder decision, not a severity score.

Exploitation
Active
none · proof-of-concept · active
Automatable
Yes
can an attacker script the kill-chain steps
Technical impact
Partial
partial · total control of the vulnerable component

Remediation

Fixes and mitigations documented by the sources — linked to the original advisory.

No fix documented by the sources we poll. That does not mean none exists: check the vendor advisory.

CISA required action CISA

Apply updates per vendor instructions.

US federal deadline: Mar 17, 2022 — passed 1673 day(s) ago

First 24 hours

Ordered from the record’s own fields — exposure first, because you cannot patch what you have not found. A rule-generated starting point.

  1. Identify exposed assets running the affected vendor/product/version combinations (Cisco Ios, Cisco Ios Xe).
  2. Treat as emergency remediation: the CVE is in CISA KEV (confirmed exploitation).
  3. The attack is network-based and needs no privileges: restrict exposure (ACLs, VPN, WAF) until patched.
  4. No fix documented in the sources: reduce exposure and monitor the vendor advisory.
  5. EPSS ahead of 95% of scored CVEs: prioritize it in the patch queue.
  6. Search available logs for exploit probes, errors and authentication anomalies.

Affected scope

Vendor, product and versions as the sources word them.

VendorProductVersionsStatusSource
Cisco Ios version 3.6(2)e Vulnerable NIST National Vulnerability Database
Cisco Ios Xe version 3.6(2)e Vulnerable NIST National Vulnerability Database

Attack characteristics

The CVSS vector, decoded. It describes the attack, not your exposure to it.

Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
Changed
Confidentiality
None
Integrity
None
Availability
High

Every base score collected

Sources score independently and may disagree; each row says who scored it and under which version.

ScoreVersionSeverityExpl.ImpactScored by
8.6 CVSS 3.1 High 3.9 4.0 nvd@nist.gov via NIST National Vulnerability Database
8.6 CVSS 3.1 High 3.9 4.0 134c704f-9b21-4f2e-91b3-4a467353bcc0 via NIST National Vulnerability Database
8.6 CVSS 3.1 High — — GitHub, Inc. via GitHub Security Advisories
8.6 CVSS 3.1 High — — CISA-ADP via CVE Program (cve.org) e CISA ADP
7.8 CVSS 2.0 High 10.0 6.9 nvd@nist.gov via NIST National Vulnerability Database
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H (score shown at the top: nvd@nist.gov)

Weakness MITRE

Weakness class according to MITRE’s CWE catalog.

CWE-755

Other CVEs with this weakness →

CISA KEV details CISA

CISA lists a CVE once it has evidence of exploitation against real targets.

Listed
Mar 3, 2022
Federal deadline
Mar 17, 2022
passed 1673 day(s) ago
Ransomware use
Unknown

CISA records ransomware use only for campaigns it has confirmed, so “Unknown” means unrecorded, not ruled out. The deadline binds US federal agencies; for everyone else it is a reference date.

EPSS over time FIRST

Oct 13, 2026 → Oct 14, 2026 · 2 reading(s) · max 7.74%

Detection

Read off the CVSS vector and the weakness class. Starting points, not tested rules.

  • Prioritize edge telemetry for the network-reachable component (proxy, WAF, IDS/IPS).
  • Hunt retroactively in logs from before Mar 3, 2022 (KEV listing): exploitation may have started earlier.
web/proxy/WAF logsnetwork IDS/IPS

Timeline

What happened to this CVE, newest first.

  • 2026
  • SSVC assessment updated
    Oct 13, 2026 · CVE Program (cve.org) e CISA ADP
  • Record published
    Oct 13, 2026
  • Affected products added · cisco/ios, cisco/ios xe
    Oct 13, 2026 · NIST National Vulnerability Database
  • CVSS changed · 8.6
    Oct 13, 2026 · NIST National Vulnerability Database
  • Source status changed · → Analyzed
    Oct 13, 2026 · NIST National Vulnerability Database
  • Added to CISA KEV (detected)
    Oct 13, 2026 · CISA Known Exploited Vulnerabilities
  • Record created in this database
    Oct 13, 2026 · CISA Known Exploited Vulnerabilities
  • 2022
  • Added to CISA KEV catalog
    Mar 2, 2022 · CISA
  • 2018
  • CVE published
    Mar 28, 2018 · cisco

Source activity

Repeated readings are counted rather than listed.

  • 2× References added · Oct 13, 2026 – Oct 13, 2026
  • 1× Official description updated · Oct 13, 2026 – Oct 13, 2026

References

7 on the record

Elsewhere on this site

Cisco
every CVE for this vendor
2022-03
what else CISA listed that month
CWE-755
other pages naming this weakness

Related CVEs (same products)

  • CVE-2026-20125 A vulnerability in the HTTP Server feature of Cisco IOS Software and Cisco IOS XE… Mar 25, 2026
  • CVE-2026-20104 A vulnerability in the bootloader of Cisco IOS XE Software for Cisco Catalyst 9200… Mar 25, 2026
  • CVE-2026-20084 Uncontrolled Resource Consumption in Cisco Ios Xe Mar 25, 2026
  • CVE-2026-20012 Missing Release of Memory after Effective Lifetime in Cisco Secure Firewall Threat Defense Mar 25, 2026
  • CVE-2026-20004 A vulnerability in the TLS library of Cisco IOS XE Software could allow an… Mar 25, 2026
  • CVE-2025-20352 Cisco IOS and IOS XE Software SNMP Denial of Service and Remote Code Execution Vulnerability KEV Sep 24, 2025

Not in any source we poll

Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.

  • No fixed version, patch or mitigation documented.
  • No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
  • No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
  • No exploit packet captures, log samples, or incident case IDs supplied.

Answered from this record

Text assembled only from the fields above — no additional claims.

What should defenders know first?

CVE-2018-0155 is "Cisco Catalyst Bidirectional Forwarding Detection Denial-of-Service Vulnerability", rated High. It affects Ios (Cisco); versions are in the scope table. It is in CISA KEV: there is evidence of real-world exploitation. CVSS 8.6 describes technical severity. EPSS 7.74% estimates the probability of exploitation in 30 days; neither replaces your asset context. First verify whether exposed or business-critical assets run the affected versions, apply vendor fixes or mitigations, and preserve logs for review.

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