Debian LinuxOperating system · Debian
CVE-2017-8821
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 · uneditedIn Tor before 0.2.5.16, 0.2.6 through 0.2.8 before 0.2.8.17, 0.2.9 before 0.2.9.14, 0.3.0 before 0.3.0.13, and 0.3.1 before 0.3.1.9, an attacker can cause a denial of service (application hang) via crafted PEM input that signifies a public key requiring a password, which triggers an attempt by the OpenSSL library to ask the user for the password, aka TROVE-2017-011.
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 denial of service vulnerability in Tor allows remote attackers to cause application hang by providing crafted PEM input that represents a password-protected public key. When Tor processes this input, OpenSSL attempts to prompt for a password, which causes the application to hang in non-interactive contexts.
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
= 8.0= 9.0< 0.2.5.16>= 0.2.6, < 0.2.8.17>= 0.2.9, < 0.2.9.14>= 0.3.0, < 0.3.0.13>= 0.3.1, < 0.3.1.9CVSS 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:3.0/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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Check installed Tor versionRun `tor --version` or check your package manager (dpkg -l tor, rpm -q tor)Affected if The version is less than 0.2.5.16, or falls between 0.2.6 and 0.2.8.x before 0.2.8.17, between 0.2.9 and 0.2.9.x before 0.2.9.14, between 0.3.0 and 0.3.0.x before 0.3.0.13, or between 0.3.1 and 0.3.1.x before 0.3.1.9
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Verify Tor is runningCheck process status with `ps aux | grep tor` or `systemctl status tor`Affected if Tor is not currently running - the vulnerability only applies to active instances
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Confirm relay or bridge configurationInspect your Tor configuration file (typically /etc/tor/torrc) for ORPort, Bridge, or ExitRelay directivesAffected if Tor is configured as a relay, bridge, or exit node, as this increases the likelihood of processing untrusted PEM input from the network
You are affected if your Tor version falls within the vulnerable ranges AND Tor is actively running, particularly as a relay or bridge that processes external descriptors.
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 data0.2.5.160.2.8.170.2.9.14
Upgrade to Tor version 0.2.5.16, 0.2.8.17, 0.2.9.14, 0.3.0.13, 0.3.1.9 or later, which includes proper handling of password-protected PEM keys without blocking.
Fix this in Debian Linux
Scoped from the published advisory
- Consultation2.0 h
- Implementation4.0 h
- Testing3.0 h
- Review / QA1.0 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-2017-8821 — 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-2017-8821 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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