CVE-2021-46853
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 · uneditedAlpine before 2.25 allows remote attackers to cause a denial of service (application crash) when LIST or LSUB is sent before STARTTLS.
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 confidenceAlpine email client before version 2.25 contains a denial-of-service vulnerability where a remote malicious IMAP server can crash the client by sending LIST or LSUB IMAP commands before the STARTTLS encryption handshake is completed. This is a protocol handling flaw in how Alpine processes unencrypted IMAP responses.
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< 2.25CVSS 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
- High
- Privileges
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- None
- Integrity
- None
- Availability
- High
CVSS:3.1/AV:N/AC:H/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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Determine Alpine versionRun 'alpine -v' or 'alpine --version' to see the installed version numberAffected if Version is below 2.25 (for example, 2.24, 2.23, etc.)
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Identify configured IMAP accountsReview Alpine configuration files (typically ~/.pinerc or ~/.alpineicep) for IMAP server entries under the 'inbox-path' or 'folder-collections' settingsAffected if Any IMAP server is configured and version is below 2.25
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Check IMAP connection settingsExamine Alpine's IMAP configuration for whether TLS/SSL is enforced. Look for 'ssl-force' or 'tls' parameters in the IMAP server definitionAffected if TLS is not enforced or server allows unencrypted connections and version is below 2.25
A user is affected if Alpine version is below 2.25 and they have IMAP accounts configured, particularly if TLS enforcement is not enabled on those connections.
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 · scoped2.25
Upgrade Alpine to version 2.25 or later. Until upgraded, users should avoid connecting to untrusted or suspicious IMAP servers and ensure TLS verification is enabled.
Alpine 2.25 or later
- 1. Check the currently installed Alpine version by running: alpine -v or alpine --version
- 2. For Alpine Linux/Edge: update the package index with: apk update
- 3. Upgrade Alpine to version 2.25 or later using: apk upgrade alpine
- 4. Verify the new version is installed: alpine -v
- 5. Test that Alpine launches correctly after upgrade
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation2.0 h
- Implementation1.0 h
- Testing2.0 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 $1,696.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-46853 — 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-2021-46853 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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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