CVE-2023-21646
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 · uneditedTransient DOS in Modem while processing invalid System Information Block 1.
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 denial of service vulnerability exists in cellular modem firmware where processing an invalid LTE System Information Block 1 (SIB1) message causes the modem to become temporarily unresponsive. The modem fails to properly handle malformed SIB1 data during the initial cell acquisition procedure, leading to a transient crash or hang condition.
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 dataall versionsall versionsall versionsall versionsall versionsall versionsall versionsall versionsCVSS 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 cellular modem hardware in useCheck system documentation, hardware inventory, or run commands such as 'lspci', 'lsusb', 'at commands' (e.g., 'AT+CGMM' or 'AT+QCFG="imei"') to identify the modem model. Alternatively, inspect the device SKU or board schematics.Affected if The modem is one of: Qualcomm Ar8035, Qca6390, Qca6391, Qca6574a, Qca6595au, Qca6696, Qca8081, or Qca8337
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Confirm the modem firmware versionQuery the modem firmware version using AT commands such as 'AT+CGMR', 'AT+QFWVER?', or vendor-specific commands. Compare the returned version against the affected product list.Affected if The modem firmware matches any of the listed affected Qualcomm products (all versions are impacted)
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Monitor for modem unresponsiveness eventsCheck system logs (dmesg, journalctl, or vendor-specific logs) for messages indicating modem crashes, resets, or hang conditions. Look for patterns around cell acquisition or network registration failures.Affected if The modem exhibits transient crashes, hangs, or unresponsiveness during or after cell search/acquisition procedures
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Inspect for SIB1 processing failuresReview modem diagnostic logs or radio layer logs for SIB1-related errors, decoding failures, or malformed message indicators. Use vendor debugging tools if available.Affected if Logs show repeated SIB1 parsing failures or error messages related to LTE System Information Block 1 processing
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Verify cellular connectivity stabilityMonitor cellular connection status via network manager logs, ping tests to cellular gateway, or periodic 'AT+CREG?' / 'AT+CEREG?' queries to detect registration failures or prolonged out-of-service periods.Affected if The device experiences unexplained loss of cellular connectivity, especially during initial network attachment or after cell reselection
A user is affected if their system contains any of the listed Qualcomm modem chips (Ar8035, Qca6390, Qca6391, Qca6574a, Qca6595au, Qca6696, Qca8081, Qca8337) and they observe modem unresponsiveness or connectivity issues consistent with the SIB1 processing vulnerability.
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 vendor-provided firmware/patch updates for the affected modem hardware. Until patched, monitor for modem availability issues that may indicate exploitation attempts via malicious base station signaling.
- Consultation4.0 h
- Implementation16.0 h
- Testing12.0 h
- Review / QA4.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2023-21646 — 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-2023-21646 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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