CVE-2017-6663: Cisco IOS Software and Cisco IOS XE Software Denial-of-Service Vulnerability

50

High

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 2.1% (30-day exploitation probability)+12
Technical severity (medium)+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

2.12%

ahead of 81% of scored CVEs · Oct 14, 2026

Affects

Cisco

Ios and 1 more

CVSS base

6.5

Medium · 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

No

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 24, 2022 — passed 1666 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.

Identify exposed assets running the affected vendor/product/version combinations (Cisco Ios, Cisco Ios Xe).
Treat as emergency remediation: the CVE is in CISA KEV (confirmed exploitation).
No fix documented in the sources: reduce exposure and monitor the vendor advisory.
Search available logs for exploit probes, errors and authentication anomalies.

Affected scope

Vendor, product and versions as the sources word them.

Vendor	Product	Versions	Status	Source
Cisco	Ios	version 15.6(2)sversion 15.6(2)sp1version 15.6(2)spversion 15.6(2)snversion 15.6(2)s4version 15.6(2)s3version 15.6(2)s2version 15.6(2)s1 and 109 more version 15.6(2)s0aversion 15.6(2)sp1bversion 15.6(1)t2version 15.6(1)t1version 15.6(1)t0aversion 15.6(1)tversion 15.6(1)s4version 15.6(1)s3version 15.6(1)s2version 15.6(2)t3version 15.7(3)mversion 15.6(3)m3version 15.6(3)m2aversion 15.6(3)m2version 15.6(3)m1bversion 15.6(3)m1version 15.6(3)m0aversion 15.6(3)mversion 15.6(1)s1aversion 15.6(2)t2version 15.6(2)t1version 15.6(2)tversion 15.6(2)sp3version 15.6(2)sp2aversion 15.6(2)sp2version 15.6(2)sp1cversion 15.5(1)s2version 15.5(3)sversion 15.5(2)s4version 15.5(2)s3version 15.5(2)s2version 15.5(2)s1version 15.5(2)sversion 15.5(1)s4version 15.5(1)s3version 15.5(3)s0aversion 15.5(1)s1version 15.5(1)sversion 15.4(3)s8version 15.4(3)s7aversion 15.4(3)s7version 15.4(3)s6bversion 15.4(3)s6aversion 15.4(3)s6version 15.5(3)s1version 15.5(3)s1aversion 15.5(3)s2version 15.5(3)s2aversion 15.5(3)s2bversion 15.5(3)s3version 15.5(3)s3aversion 15.5(3)s4version 15.5(3)s4aversion 15.5(3)s4bversion 15.5(3)s4dversion 15.5(3)s5version 15.5(3)snversion 15.6(1)sversion 15.6(1)s1version 15.2(3)eversion 15.2(3)e1version 15.2(3)e2version 15.2(3)e3version 15.2(3)e4version 15.2(3)e5version 15.2(3a)eversion 15.2(3a)e1version 15.2(3m)e2version 15.2(3m)e3version 15.2(3m)e6version 15.2(3m)e8version 15.2(4)eversion 15.2(4)e1version 15.2(4)e2version 15.2(4)e3version 15.2(5)eversion 15.2(5)e1version 15.2(5a)eversion 15.2(5b)eversion 15.3(3)sversion 15.3(3)s1version 15.3(3)s1aversion 15.3(3)s2version 15.3(3)s3version 15.3(3)s4version 15.3(3)s5version 15.3(3)s6version 15.3(3)s7version 15.3(3)s8version 15.3(3)s8aversion 15.3(3)s9version 15.3(3)s10version 15.4(1)sversion 15.4(1)s1version 15.4(1)s2version 15.4(1)s3version 15.4(1)s4version 15.4(2)sversion 15.4(2)s1version 15.4(2)s2version 15.4(2)s3version 15.4(2)s4version 15.4(3)sversion 15.4(3)s1version 15.4(3)s2version 15.4(3)s3version 15.4(3)s4version 15.4(3)s5version 15.4(3)s5a	Vulnerable	NIST National Vulnerability Database
Cisco	Ios Xe	version 3.7.0eversion 3.7.1eversion 3.7.3eversion 3.8.0eversion 3.8.0exversion 3.8.1eversion 3.8.2eversion 3.8.3e and 61 more version 3.9.0eversion 3.9.1eversion 3.10.4sversion 3.10.8asversion 3.10.8sversion 3.11.3sversion 3.11.4sversion 3.12.0asversion 3.12.0sversion 3.12.1sversion 3.12.2sversion 3.12.3sversion 3.12.4sversion 3.13.0sversion 3.13.1sversion 3.13.2asversion 3.13.2sversion 3.13.4sversion 3.13.5asversion 3.13.5sversion 3.13.6asversion 3.13.6sversion 3.13.7asversion 3.13.8sversion 3.14.0sversion 3.14.1sversion 3.14.2sversion 3.14.3sversion 3.14.4sversion 3.15.0sversion 3.15.1sversion 3.15.2sversion 3.15.3sversion 3.15.4sversion 3.16.0sversion 3.16.1asversion 3.16.2asversion 3.16.2sversion 3.16.3asversion 3.16.3sversion 3.16.4asversion 3.16.4dsversion 3.16.4sversion 3.16.6sversion 3.17.0sversion 3.17.1asversion 3.17.1sversion 3.17.3sversion 3.17.4sversion 3.18.0asversion 3.18.0sversion 3.18.0spversion 3.18.1bspversion 3.18.1sversion 3.18.1spversion 3.18.2aspversion 3.18.2sversion 3.18.2spversion 3.18.3sversion 3.18.3spversion 16.6.1	Vulnerable	NIST National Vulnerability Database

Attack characteristics

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

Attack vector

Adjacent

Attack complexity

Low

Privileges required

None

User interaction

None

Scope

Unchanged

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.

Score	Version	Severity	Expl.	Impact	Scored by
6.5	CVSS 3.1	Medium	2.8	3.6	nvd@nist.gov via NIST National Vulnerability Database
6.5	CVSS 3.1	Medium	2.8	3.6	134c704f-9b21-4f2e-91b3-4a467353bcc0 via NIST National Vulnerability Database
6.5	CVSS 3.1	Medium	—	—	CISA-ADP via CVE Program (cve.org) e CISA ADP
6.5	CVSS 3.0	Medium	—	—	GitHub, Inc. via GitHub Security Advisories
6.1	CVSS 2.0	Medium	6.5	6.9	nvd@nist.gov via NIST National Vulnerability Database

CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H (score shown at the top: nvd@nist.gov)

CISA KEV details CISA

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

Listed

Mar 3, 2022

Federal deadline

Mar 24, 2022

passed 1666 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 2.12%

Detection

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

Hunt retroactively in logs from before Mar 3, 2022 (KEV listing): exploitation may have started earlier.

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 · 6.5
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
2017
CVE published
Aug 7, 2017 · 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

6 on the record

tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20170726-anido
Vendor Advisory, x_refsource_CONFIRM, NIST National Vulnerability Database
www.cisa.gov/known-exploited-vulnerabilities-catalog
US Government Resource, NIST National Vulnerability Database
www.securityfocus.com/bid/99973
Broken Link, Third Party Advisory, VDB Entry, vdb-entry, x_refsource_BID, NIST National Vulnerability Database
github.com/advisories/GHSA-3h3r-w377-6ffg
GitHub Security Advisories
www.securitytracker.com/id/1038999
Broken Link, Third Party Advisory, VDB Entry, vdb-entry, x_refsource_SECTRACK, NIST National Vulnerability Database
nvd.nist.gov/vuln/detail/CVE-2017-6663
GitHub Security Advisories

Elsewhere on this site

Cisco
every CVE for this vendor

2022-03
what else CISA listed that month

Related CVEs (same products)

High CVE-2026-20301 Cisco IOS Software and IOS XE Software Extensible Messaging Client Protocol Denial of Service Vulnerability Aug 5, 2026
Critical CVE-2026-20272 Cisco IOS XE Software Security Hardening Release Aug 5, 2026
High CVE-2026-20273 Cisco IOS XE Software Security Hardening Release Aug 5, 2026
High CVE-2026-20269 Cisco IOS XE Software Security Hardening Release Aug 5, 2026
High CVE-2026-20270 Cisco IOS XE Software Security Hardening Release Aug 5, 2026
High CVE-2026-20271 Cisco IOS XE Software Security Hardening Release Aug 5, 2026

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 CWE classification.
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-2017-6663 is "Cisco IOS Software and Cisco IOS XE Software Denial-of-Service Vulnerability", rated Medium. It affects Ios (Cisco); versions are in the scope table. It is in CISA KEV: there is evidence of real-world exploitation. CVSS 6.5 describes technical severity. EPSS 2.12% 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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