Debian LinuxOperating system · Debian
CVE-2019-25035
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 · uneditedUnbound before 1.9.5 allows an out-of-bounds write in sldns_bget_token_par. NOTE: The vendor disputes that this is a vulnerability. Although the code may be vulnerable, a running Unbound installation cannot be remotely or locally exploited
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 confidenceUnbound DNS server before version 1.9.5 contains an out-of-bounds write vulnerability in the sldns_bget_token_par function, which handles token parsing. This memory corruption issue carries a CVSS 9.8 critical rating, though the vendor disputes both the vulnerability classification and exploitability.
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
Debian LinuxOperating system
= 9.0< 1.9.5CVSS 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
- High
- Availability
- High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/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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Check if Unbound DNS server is installedRun `unbound -V` or `unbound-control status` to see version information. On Debian, also check with `dpkg -l | grep unbound`Affected if Unbound is installed and version is below 1.9.5
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Verify the exact installed version numberCompare the version output against the affected range. Any version prior to 1.9.5 (such as 1.9.4, 1.9.3, 1.9.2, 1.8.x, 1.7.x, 1.6.x, 1.5.x, 1.4.x) is within the vulnerable rangeAffected if Installed version is less than 1.9.5 (for example, 1.9.4, 1.8.3, etc.)
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Confirm Unbound is actively running as a DNS serviceCheck if Unbound is listening on port 53 with `netstat -tulpn | grep unbound` or `ss -tulpn | grep :53`Affected if Unbound is running as a DNS server and the version is below 1.9.5
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Check for zone file or config file processingThe vulnerability is in sldns_bget_token_par which handles token parsing. Inspect if Unbound is parsing zone files or complex configurations with `unbound-control list_zones`Affected if Unbound is processing zone data or parsing configuration files and version is below 1.9.5
Your environment is affected if Unbound DNS server is installed and running with any version lower than 1.9.5, regardless of the Debian version.
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.
dbcve · scoped1.9.5
Upgrade Unbound to version 1.9.5 or later; the vendor claims no remote or local exploitation is possible in practice, but the high CVSS score warrants the upgrade as a precautionary measure.
Unbound 1.9.5 or later (Debian 9.0: apply latest unbound package from Debian security updates)
- Check current Unbound version: unbound -version or dpkg -l | grep unbound
- For Debian 9.0: Run 'apt update && apt install unbound' to apply available security updates
- If installing from source, download Unbound 1.9.5 or later from https://www.unbound.net/downloads/
- Verify the upgrade: unbound -version should show version 1.9.5 or higher
- Restart the Unbound service: systemctl restart unbound (or service unbound restart)
Generated from the published advisory — verify against the referenced sources before acting.
Fix this in Debian Linux
Scoped from the published advisory
- Consultation2.0 h
- Implementation3.0 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 $2,800.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2019-25035 — 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-2019-25035 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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