Ios XeOperating system · Cisco
CVE-2024-20436
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 · uneditedA vulnerability in the HTTP Server feature of Cisco IOS XE Software when the Telephony Service feature is enabled could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on an affected device. This vulnerability is due to a null pointer dereference when accessing specific URLs. An attacker could exploit this vulnerability by sending crafted HTTP traffic to an affected device. A successful exploit could allow the attacker to cause the affected device to reload, causing a DoS condition on the affected device.
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 confidenceA null pointer dereference vulnerability exists in the HTTP Server feature of Cisco IOS XE Software when the Telephony Service is enabled. An unauthenticated remote attacker can exploit this by sending crafted HTTP traffic to specific URLs, causing the affected device to reload and result in a denial of service.
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
Ios XeOperating system
= 3.9.0as= 3.9.1s= 3.9.2s= 3.10.0s= 3.10.1s= 3.10.2s= 3.10.2ts= 3.10.3s= 3.10.4s= 3.10.5s= 3.10.6s= 3.10.7sCVSS 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
- None
- Integrity
- None
- Availability
- High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
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 checksWork through these to decide whether this CVE applies to you.
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Identify the Cisco IOS XE versionRun 'show version' or 'show version | include IOS XE' command to obtain the software versionAffected if Version falls outside the 3.9.0as through 3.10.7s range (not affected if version is different)
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Confirm Telephony Service is enabledRun 'show telephony-service' or check configuration for 'telephony-service' under global configuration modeAffected if Telephony Service is configured and active - this is the required condition for the vulnerability to be exploitable
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Verify HTTP Server is enabledRun 'show ip http server status' or check configuration for 'ip http server' commandAffected if HTTP server is enabled and Telephony Service is also enabled (both conditions required)
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Check for recent unexpected reloadsReview system logs and 'show logging' output for unexpected reload events around the time of potential HTTP attacksAffected if Device has reloaded unexpectedly with HTTP-related crash info in logs
A device is affected if it runs Cisco IOS XE versions 3.9.0as through 3.10.7s AND has Telephony Service enabled with HTTP Server accessible.
Generated from the published advisory. Verify against your own configuration.
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.
From vendor dataApply the Cisco IOS XE software update when available. As a workaround, disable the Telephony Service feature if not required, and restrict HTTP server access to trusted sources using ACLs.
Fix this in Ios Xe
Scoped from the published advisory
- Consultation4.0 h
- Implementation4.0 h
- Testing2.0 h
- Review / QA2.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $3,488.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2024-20436 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2024-20436 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- Verified mitigations, workarounds, and config changes
- Version or environment caveats, and links to real fixes
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