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ThunderbirdApplication · Mozilla

CVE-2026-57962

MEDIUM · 5.3 CVSS v3.1 Published 2026-07-01
Fix available
A fix is available. Upgrade to 140.12.1 / 152.0.1 or later.
See remediation →
60/100
Remediation priority · Elevated
Remotely reachable No privileges 7 weeks old

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
A malicious LDAP server, which a Thunderbird user is configured to query for address-book autocomplete, can stash arbitrarily large amounts of attacker-supplied data into the Thunderbird LDAP client until it crashes due to memory exhaustion. This vulnerability was fixed in Thunderbird 152.0.1 and Thunderbird 140.12.1.

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

Thunderbird contains a denial-of-service vulnerability in its LDAP client component used for address-book autocomplete. When Thunderbird queries a malicious LDAP server for address book lookups, the server can respond with arbitrarily large amounts of data, causing memory exhaustion and client crash.

MitigationUpdate Thunderbird to version 152.0.1 or 140.12.1 or later. Users should verify their configured LDAP servers are trusted and consider disabling LDAP address-book autocomplete if not required.

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
ThunderbirdApplication
Affected:< 140.12.1< 152.0.1

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
High
Privileges
None
User interaction
Required
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:N/AC:H/PR:N/UI:R/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. Check installed Thunderbird version
    Open Thunderbird, go to Help > About Thunderbird (or on macOS Thunderbird > About Thunderbird) to see the exact version number. Alternatively, check your system's installed programs list or package manager.
    Affected if The version is below 140.12.1 or below 152.0.1 (note: 152.x is a separate release track from 140.x)
  2. Check for LDAP address book configuration
    In Thunderbird, go to Edit > Account Settings > Composition & Addressing, or check the Address Books panel (View > Folded Accounts). Look for any LDAP address books listed.
    Affected if Any LDAP address book is configured and enabled in the account settings
  3. Verify LDAP server connection settings
    In Account Settings, select the LDAP address book and click Edit Directory. Note the server hostname configured. This is the server Thunderbird would query for autocomplete.
    Affected if An LDAP server hostname is configured and the address book is enabled for autocomplete

You are affected if your Thunderbird version is below 140.12.1 or below 152.0.1 AND you have an LDAP address book enabled with a configured server (especially an untrusted or external LDAP server).

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.

dbcve · scoped
Upgrade available Upgrade to 140.12.1 / 152.0.1 or later
Fixed in 140.12.1152.0.1
Interim mitigation

Update Thunderbird to version 152.0.1 or 140.12.1 or later. Users should verify their configured LDAP servers are trusted and consider disabling LDAP address-book autocomplete if not required.

Recommended fix High confidence

Thunderbird 140.12.1 (ESR branch) or Thunderbird 152.0.1 (release branch)

  1. Check current Thunderbird version by going to Help > About Thunderbird
  2. Upgrade Thunderbird to version 140.12.1 or higher (if using the 140.x ESR branch)
  3. Alternatively, upgrade to version 152.0.1 or higher (if using the 152.x release branch)
  4. Download from the official Mozilla Thunderbird website: www.mozilla.org/thunderbird/
  5. Restart Thunderbird after upgrade to ensure the fix is applied

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Thunderbird Scoped from the published advisory
  • Consultation2.0 h
  • Implementation8.0 h
  • Testing4.0 h
  • Review / QA2.0 h
16.0 hours of engineering $2,800
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An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $4,480.

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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-2026-57962 in production — separate from our analysis above.

No notes yet

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What this is

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.

What belongs here
  • 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