CVE-2021-21723
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 · uneditedSome ZTE products have a DoS vulnerability. Due to the improper handling of memory release in some specific scenarios, a remote attacker can trigger the vulnerability by performing a series of operations, resulting in memory leak, which may eventually lead to device denial of service. This affects: ZXR10 9904, ZXR10 9908, ZXR10 9916, ZXR10 9904-S, ZXR10 9908-S; all versions up to V1.01.10.B12.
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 · moderate confidenceA memory leak vulnerability in ZTE ZXR10 9904/9908/9916/9904-S/9908-S routers allows remote attackers to cause denial of service by exploiting improper memory release handling in specific scenarios. Repeated exploitation leads to memory exhaustion and device 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<= v1.01.10.b12<= v1.01.10.b12<= v1.01.10.b12<= v1.01.10.b12<= v1.01.10.b12CVSS 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 exact ZXR10 router modelLog into the device CLI or web interface and retrieve the hardware model designation. Confirm it is one of: ZXR10 9904, 9908, 9916, 9904-S, or 9908-S.Affected if The device model matches any of the affected variants listed.
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Check the installed firmware versionAccess the device management interface and navigate to the system information or firmware version section. Record the exact firmware version string.Affected if The firmware version is v1.01.10.b12 or any version lower than that (for example, v1.01.09, v1.01.08, etc.).
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Verify memory usage and stabilityUse device diagnostics or SNMP monitoring to observe memory utilization over time. Look for steadily increasing memory consumption without release, and check for unexpected device reboots or crashes in system logs.Affected if Memory usage grows abnormally without returning to baseline, or device crash logs correlate with memory exhaustion events.
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Assess network exposureReview firewall rules, access control lists, and interface configurations to determine if the vulnerable management interfaces are reachable from untrusted networks.Affected if The device management interfaces are accessible from external networks without adequate filtering.
You are affected if your ZXR10 router is model 9904, 9908, 9916, 9904-S, or 9908-S and runs firmware version v1.01.10.b12 or lower, especially if the device shows signs of memory exhaustion or is directly exposed to remote attackers.
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 dataContact ZTE for the patched firmware version beyond V1.01.10.B12 and apply the update following vendor guidelines. If no patch is available, implement network segmentation and traffic filtering to limit exposure to remote attackers.
- Consultation4.0 h
- Implementation4.0 h
- Testing8.0 h
- Review / QA2.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-21723 — 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-2021-21723 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
- No weaponised exploit code, or anything meant to cause harm
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