FedoraOperating system · Fedoraproject
CVE-2020-15917
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 · uneditedcommon/session.c in Claws Mail before 3.17.6 has a protocol violation because suffix data after STARTTLS is mishandled.
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 confidenceIn Claws Mail versions before 3.17.6, the session.c component mishandles suffix data following the STARTTLS command during SMTP/IMAP connection establishment. This protocol violation could allow an attacker to inject or intercept data during the TLS upgrade process, potentially enabling man-in-the-middle attacks or session hijacking.
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
FedoraOperating system
= 31= 32< 3.17.6= 15.0= 15.1= 15.2CVSS 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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Determine installed Claws Mail versionRun 'claws-mail --version' from command line or open Claws Mail and go to Help > About to view the version numberAffected if The reported version is less than 3.17.6 (for example, 3.17.5, 3.17.4, or earlier)
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Identify accounts using STARTTLSIn Claws Mail, navigate to Configuration > Account Settings and examine each configured account. Check the SMTP and IMAP server settings for STARTTLS or TLS encryption optionsAffected if Any mail account is configured to use STARTTLS for SMTP or IMAP connections
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Verify STARTTLS availability in buildCheck if your Claws Mail binary was built with STARTTLS support by running 'claws-mail --version 2>&1 | grep -i tls' or inspecting the application's encryption capabilities in the About dialogAffected if STARTTLS support is compiled into the application
You are affected if your Claws Mail version is below 3.17.6 AND you have accounts configured to use STARTTLS for SMTP or IMAP connections, as the protocol mishandling only occurs during TLS upgrade processes.
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 · scoped3.17.6
Upgrade Claws Mail to version 3.17.6 or later to address the STARTTLS protocol handling vulnerability.
Claws Mail 3.17.6
- For Fedora systems: Run 'sudo dnf update claws-mail' or 'sudo dnf upgrade claws-mail' to upgrade to the latest version containing the fix.
- For openSUSE Leap and SUSE Backports: Run 'sudo zypper update claws-mail' or 'sudo zypper patch' to apply security updates.
- Verify the installed version by running 'claws-mail --version' and ensure it shows version 3.17.6 or later.
- Alternatively, download the source code from git.claws-mail.org and compile version 3.17.6 or later.
Generated from the published advisory — verify against the referenced sources before acting.
Fix this in Fedora
Scoped from the published advisory
- Consultation2.0 h
- Implementation4.0 h
- Testing4.0 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 $3,328.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2020-15917 — 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-2020-15917 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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