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Actively exploited in the wild. This CVE is on the CISA Known Exploited Vulnerabilities list — treat remediation as urgent. Federal remediation due by 9 Jun 2023.
iOSOperating system · Cisco

CVE-2016-6415

HIGH · 7.5 CVSS v3.1 Published 2016-09-19
Fix available
A fix is available. Upgrade to 5.3.0 or later.
See remediation →
100/100
Remediation priority · Urgent
In the wild High EPSS Remotely reachable No privileges Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
The server IKEv1 implementation in Cisco IOS 12.2 through 12.4 and 15.0 through 15.6, IOS XE through 3.18S, IOS XR 4.3.x and 5.0.x through 5.2.x, and PIX before 7.0 allows remote attackers to obtain sensitive information from device memory via a Security Association (SA) negotiation request, aka Bug IDs CSCvb29204 and CSCvb36055 or BENIGNCERTAIN.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

This is an information disclosure vulnerability in Cisco's IKEv1 server implementation across IOS, IOS XE, IOS XR, and legacy PIX platforms. An unauthenticated remote attacker can send a crafted Security Association (SA) negotiation request to leak sensitive information from device memory, potentially exposing keys or credentials.

MitigationApply the appropriate Cisco security updates for your specific platform and version. If patches are unavailable, consider disabling IKEv1 if not required, or implement network-level access controls to limit IKE traffic to trusted sources.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
iOSOperating system
Affected:>= 12.2, <= 12.4>= 15.0, <= 15.6
Ios XeOperating system
Affected:<= 3.18s
Ios XrOperating system
Affected:>= 4.3.0, <= 4.3.4>= 5.0.0, < 5.3.0

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
None
Availability
None

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify the platform and version
    Use 'show version' command to determine if the device runs Cisco iOS, IOS XE, or IOS XR, and note the exact software version number.
    Affected if The version falls within the affected ranges: iOS 12.2-12.4 or 15.0-15.6, IOS XE <=3.18s, or IOS XR 4.3.0-4.3.4 or 5.0.0-5.2.x
  2. Verify IKEv1 is enabled
    Check the configuration with 'show crypto isakmp sa' and look for active IKEv1 Security Associations, or review the configuration with 'show running-config | include crypto isakmp' to see if IKEv1 policies are defined.
    Affected if IKEv1 policies exist or active IKEv1 SAs are present, indicating the IKEv1 server feature is enabled and negotiating
  3. Confirm IKEv1 responder configuration
    Review crypto configuration with 'show crypto isakmp policy' to identify if the device is configured to accept IKEv1 connections from remote peers.
    Affected if Any IKEv1 policy is configured that allows remote-initiated negotiations (especially those with 'authentication pre-share' or 'authentication rsa-sig')
  4. Check IKEv1 keyring or trustpoint bindings
    Use 'show crypto keyring' and 'show crypto isakmp profile' to see if IKEv1 keyrings or profiles are defined, indicating the device can act as an IKEv1 responder.
    Affected if IKEv1 keyrings or profiles are defined, showing the device can participate in IKEv1 negotiations as a server

The device is affected if it runs a vulnerable iOS, IOS XE, or IOS XR version AND has IKEv1 enabled with active or configured IKEv1 responder policies that accept remote SA negotiation requests.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 5.3.0 or later
Fixed in 5.3.0
Interim mitigation

Apply the appropriate Cisco security updates for your specific platform and version. If patches are unavailable, consider disabling IKEv1 if not required, or implement network-level access controls to limit IKE traffic to trusted sources.

Recommended fix High confidence

Upgrade to IOS 15.7(3)+, IOS XE 3.18.4+, or IOS XR 5.3.0+ (or latest platform-supported version)

  1. 1. Identify the current Cisco IOS/IOS XE/IOS XR version on the device using 'show version' command
  2. 2. Determine the product line (IOS, IOS XE, or IOS XR) from the version output
  3. 3. Consult the Cisco Security Advisory cisco-sa-20160916-ikev1 for the specific fixed releases for each product line
  4. 4. For IOS: Upgrade to version 15.7(3) or later, or the latest recommended release for your hardware platform
  5. 5. For IOS XE: Upgrade to version 3.18.4 or later, or version 16.x/17.x as appropriate for your hardware
  6. 6. For IOS XR: Upgrade to version 5.3.0 or later, or version 6.x/7.x as appropriate for your hardware
  7. 7. Verify the upgrade using 'show version' and confirm the new version includes the security fix
  8. 8. Test IKEv1 VPN connectivity after upgrade to ensure proper functionality
Caveat Older iOS 12.x versions may be end-of-life and not have official fixes; ensure target hardware supports the upgrade path; some legacy VPN configurations may need review

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in iOS Exploited in the wild — priority engagement
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing6.0 h
  • Review / QA2.0 h
20.0 hours of engineering $3,500
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2016-6415 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data