CVE-2020-3118
A vulnerability in the Cisco Discovery Protocol implementation for Cisco IOS XR Software could allow an unauthenticated, adjacent attacker to execute arbitrary code or cause a reload on an affected device. The vulnerability is due to improper validation of string input from certain fields in Cisco Discovery Protocol messages. An attacker could exploit this vulnerability by sending a malicious Cisco Discovery Protocol packet to an affected device. A successful exploit could allow the attacker to cause a stack overflow, which could allow the attacker to execute arbitrary code with administrative privileges on an affected device. Cisco Discovery Protocol is a Layer 2 protocol. To exploit this vulnerability, an attacker must be in the same broadcast domain as the affected device (Layer 2 adjacent).
- CVSS
- 8.8Highscored by the publisher (CNA)
- Exploited in the wild
- Yes, in CISA KEV since 3 Nov 2021CISA deadline for US federal agencies: 3 May 2022
- EPSS
- 11.7%chance of exploitation in the next 30 daystop 4% of scored CVEsFIRST score of 11 Nov 2026
- Fix
- Patch availablesee the advisories in the references
- Published
- 5 Feb 2020analysed here 12 Nov 2026
Do first. Apply updates per vendor instructions. (CISA's required action for this KEV entry)
Summary
Triage
- Attack surface
- Server-side
- Exploitable
- At runtime
- Attack vector
- adjacent network
- Can a WAF block it?
- No. See why
The summary, impact and action text on this page are written by our AI analysis pipeline, or taken from the NVD description when a CVE was imported from NVD. They are not the vendor's wording: check them against the sources. A longer AI executive summary and technical analysis are generated for signed-in accounts on the Max plan.
Affected products
| Product | Affected versions | Vendor says fixed in |
|---|---|---|
| Cisco Cisco IOS XR Software | < 6.6.3Vendor says fixed in: not stated |
As published in the CVE Program record. A version outside these ranges is not a statement that it is unaffected — vendors sometimes understate a range, and distribution-backported builds carry upstream numbers that do not reflect what was patched into them.
Products named in our analysis
- cisco:ios_xr
Fix and mitigation
WAF and other mitigations
Can a WAF block it? No. This is an out-of-bounds write, a memory-corruption bug. Generic WAF rules do not recognise the input that triggers it; only a rule written for this specific CVE can, and only if the triggering request has a recognisable shape.
Also consider: patch
Based on the weakness type only; no CVE-specific evidence yet. We check Cloudflare, AWS, Google Cloud Armor and Azure; for Akamai, Imperva, Fastly, F5, ask your vendor.
Remediation steps (AI-written)
Step-by-step remediation is generated for accounts on the Max plan, for CVEs that match a technology in their stack. Add this technology to your stack to see the fix checklist.
Exploitation evidence
- CISA KEV catalog
- Listed since 3 Nov 2021.
- CISA due date
- 3 May 2022, the remediation deadline for US federal agencies
- CISA required action
- Apply updates per vendor instructions.
- Public exploit code
- None on record in Exploit-DB, Metasploit, Nuclei templates or PoC-in-GitHub.
- CISA SSVC
- exploitation active, automatable no, technical impact totalAssessed by CISA 8 Nov 2024 (SSVC 2.0.3). Exploitation is none, poc (public proof of concept) or active.
Timeline
- 5 Feb 2020Published
- 3 Nov 2021Added to CISA KEV (exploited in the wild)636 days (about 2 years) later
- 3 May 2022CISA remediation due date (US federal agencies)181 days (about 6 months) later
- 8 Nov 2024CISA SSVC assessment: exploitation active921 days (about 3 years) later
- 21 Oct 2025CVE record last updated347 days (about 12 months) later
- 12 Nov 2026Analysed by vulneraibility.com387 days (about 1 year) later
CVSS vector
CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
| Metric | Value | What it means |
|---|---|---|
| Attack vector | AdjacentSame subnet or link layer. | Same subnet or link layer. |
| Attack complexity | LowRepeatable attack, no special conditions. | Repeatable attack, no special conditions. |
| Privileges required | NoneThe attacker needs no prior access. | The attacker needs no prior access. |
| User interaction | NoneNo victim action needed. | No victim action needed. |
| Scope | UnchangedImpact stays within the vulnerable component. | Impact stays within the vulnerable component. |
| Confidentiality | HighTotal data disclosure possible. | Total data disclosure possible. |
| Integrity | HighComplete modification possible. | Complete modification possible. |
| Availability | HighFull outage possible. | Full outage possible. |
Common questions
Is CVE-2020-3118 being exploited?
Yes. CVE-2020-3118 appears in CISA's Known Exploited Vulnerabilities catalog, which means exploitation in the wild has been confirmed and reported. Treat it as active rather than theoretical, and patch it ahead of higher-scoring vulnerabilities that carry no exploitation evidence.
How severe is CVE-2020-3118?
CVE-2020-3118 is rated High with a CVSS score of 8.8. Severity describes how bad exploitation would be, not how likely it is: pair it with exploitation evidence before deciding what to patch first.
Is there a patch for CVE-2020-3118?
Yes. A fix has been recorded for CVE-2020-3118. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2020-3118 affect?
CVE-2020-3118 affects cisco:ios_xr. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
References
3 references in the CVE record, grouped by the tags the record gives them.
Advisories (1)
- tools.cisco.com /security/center/content/CiscoSecurityAdvisory/cisco-sa-20200205-iosxr-cdp-rce
Other links (2)
- packetstormsecurity.com /files/156203/Cisco-Discovery-Protocol-CDP-Remote-Device-Takeover.html
- cisa.gov /known-exploited-vulnerabilities-catalog?field_cve=CVE-2020-3118
Where the data on this page comes from
- CVE List (CVE.org): description, affected versions, references; CVE Terms of Use
- NVD: CVSS and CPE data
- CISA KEV catalog: exploitation, date added, due date
- CISA Vulnrichment (ADP): SSVC decision points
- FIRST EPSS: exploit probability and percentile
Summary, impact and triage tags: written by our AI analysis pipeline from the sources above. Check them against the sources.
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