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Resource Allocation Without LimitsWeakness · CWE-770

CVE-2024-23185

HIGH · 7.5 CVSS v3.1 Published 2024-09-10
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
84/100
Remediation priority · High
Remotely reachable No privileges Zero-click

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 · unedited
Very large headers can cause resource exhaustion when parsing message. The message-parser normally reads reasonably sized chunks of the message. However, when it feeds them to message-header-parser, it starts building up "full_value" buffer out of the smaller chunks. The full_value buffer has no size limit, so large headers can cause large memory usage. It doesn't matter whether it's a single long header line, or a single header split into multiple lines. This bug exists in all Dovecot versions. Incoming mails typically have some size limits set by MTA, so even largest possible header size may still fit into Dovecot's vsz_limit. So attackers probably can't DoS a victim user this way. A user could APPEND larger mails though, allowing them to DoS themselves (although maybe cause some memory issues for the backend in general). One can implement restrictions on headers on MTA component preceding Dovecot. No publicly available exploits are known.

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 confidence

Dovecot's message-parser has an unbounded memory allocation vulnerability in header parsing. When building the 'full_value' buffer from chunks fed to message-header-parser, no size limit is enforced, allowing large headers to exhaust memory resources. This affects both single long header lines and multi-line headers.

MitigationImplement header size limits in the MTA preceding Dovecot to restrict incoming header sizes. Consider also adding vsz_limit constraints for userAPPEND operations.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

CVSS 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 checks

Work through these to decide whether this CVE applies to you.

  1. Identify Dovecot installation and version
    Run `dovecot --version` or check your package manager (e.g., `rpm -q dovecot`, `dpkg -l dovecot`) to obtain the installed version number
    Affected if The installed version is within any affected version range for CVE-2024-23185 (compare your version to known affected releases)
  2. Determine if LDA or LMTP services are active
    Check dovecot configuration files (typically in /etc/dovecot/) for enabled protocols, specifically looking for lda or lmtp in the protocols setting, and check if these services are running via `systemctl status dovecot` or similar
    Affected if LDA (local delivery agent) or LMTP services are enabled, as these utilize the message-header-parser component
  3. Verify incoming mail processing is handled by Dovecot
    Inspect your postfix or other MTA configuration to confirm that mail delivery routes through Dovecot (check for dovecot transport in master.cf or the dovecot LDA/LMTP socket)
    Affected if Dovecot handles mail delivery for your domain, meaning it processes incoming邮件 headers
  4. Check for existing header size limitations
    Review dovecot configuration files for any existing header size limits (look for settings like `imap_max_line_length` or custom header limits in conf.d/ files) and verify whether upstream MTA applies header size constraints
    Affected if No header size limits are configured in either Dovecot or the upstream MTA, leaving the unbounded memory allocation vulnerable to exploitation

Your environment is affected if Dovecot with an unpatched version handles incoming mail delivery via LDA or LMTP, and no external header size limits are enforced by your upstream MTA to mitigate the unbounded memory allocation in header parsing.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

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 data
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Implement header size limits in the MTA preceding Dovecot to restrict incoming header sizes. Consider also adding vsz_limit constraints for userAPPEND operations.

Have this fixed Scoped from the published advisory
  • Consultation4.0 h
  • Implementation12.0 h
  • Testing8.0 h
  • Review / QA4.0 h
28.0 hours of engineering $4,880
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2024-23185 in production — separate from our analysis above.

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What this is

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