ExpresswayApplication · Cisco
CVE-2020-3596
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 Session Initiation Protocol (SIP) of Cisco Expressway Series and Cisco TelePresence Video Communication Server (VCS) could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on an affected device. The vulnerability is due to incorrect handling of incoming SIP traffic. An attacker could exploit this vulnerability by sending a series of SIP packets to an affected device. A successful exploit could allow the attacker to exhaust memory on an affected device, causing it to crash and leading to a DoS condition.
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 confidenceThis vulnerability in Cisco Expressway Series and TelePresence VCS devices allows an unauthenticated remote attacker to crash the device by sending specially crafted SIP packets. The root cause is incorrect handling of incoming SIP traffic that leads to memory exhaustion and system crash.
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
ExpresswayApplication
<= x12.6.3
Telepresence Video Communication ServerApplication
<= x12.6.3CVSS 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.
-
Identify product typeDetermine if the device is Cisco Expressway Series or Cisco TelePresence Video Communication Server (VCS). This is typically visible in the product web interface or CLI banner.Affected if Device is either Cisco Expressway or Cisco TelePresence VCS
-
Check installed software versionAccess the device web interface (Help > About) or use CLI command 'xStatus' to retrieve the current software version. Compare against the affected range: versions <= x12.6.3 are vulnerable.Affected if Installed version is x12.6.3 or any earlier version (x12.5, x12.0, etc.)
-
Verify SIP service is enabledCheck if SIP is configured and enabled on the device. In the web interface, go to Applications > SIP or use CLI 'xConfiguration SIP' to see SIP configuration status.Affected if SIP service is enabled and the device is configured to accept SIP traffic (typically on port 5060/5061)
-
Assess network exposure of SIP portsDetermine if the device's SIP listening ports are accessible from untrusted networks. Review firewall rules and device IP access lists. Check if the device is directly exposed to the internet or receives SIP traffic from untrusted sources.Affected if SIP ports are reachable from untrusted/external networks without adequate filtering
A user is affected if they are running Cisco Expressway or TelePresence VCS at version x12.6.3 or below, with SIP enabled and accessible to untrusted networks that could send malicious SIP packets.
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 patch when available; until then, consider SIP traffic filtering at network perimeter to block malicious SIP packets from untrusted sources.
Fix this in Expressway
Scoped from the published advisory
- Consultation3.0 h
- Implementation4.0 h
- Testing3.0 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 $3,408.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2020-3596 — 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-2020-3596 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
Be the first to add a field note for this CVE — a mitigation you’ve verified, a version caveat, or a link to a working fix. Sign in above to contribute.
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.
- 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