Thunderbird Security Update — AlmaLinux 8 (ALSA-2026:13537)

ALSA-2026:13537 updates Thunderbird on AlmaLinux 8, fixing a 25-CVE Mozilla security batch (CVE-2026-6772 through CVE-2026-6776) — incorrect boundary conditions in NSS, use-after-free in the JavaScript Engine, DOM spoofing and more. Update with dnf update thunderbird and restart the client.

High 7.5 CVSS 2026-10-29

AlmaLinux 8

Was das unter einer SharedLicense-Lizenz bedeutet

Thunderbird renders untrusted email content with browser-grade engines — use-after-free and sandbox-boundary flaws in that engine are the standard malicious-email-to-code-execution chain, making mail clients a prime phishing-adjacent attack surface.

Mozilla Thunderbird is a standalone mail and newsgroup client.  

Security Fix(es):  

  * firefox: thunderbird: Incorrect boundary conditions in the Libraries component in NSS (CVE-2026-6772)
  * firefox: thunderbird: Use-after-free in the JavaScript Engine component (CVE-2026-6754)
  * firefox: thunderbird: Spoofing issue in the DOM: Core & HTML component (CVE-2026-6762)
  * firefox: thunderbird: Incorrect boundary conditions in the WebRTC component (CVE-2026-6752)
  * firefox: thunderbird: Other issue in the Storage: IndexedDB component (CVE-2026-6770)
  * firefox: thunderbird: Invalid pointer in the JavaScript: WebAssembly component (CVE-2026-6757)
  * firefox: thunderbird: Other issue in the Libraries component in NSS (CVE-2026-6767)
  * firefox: thunderbird: Memory safety bugs fixed in Firefox ESR 140.10, Thunderbird ESR 140.10, Firefox 150 and Thunderbird 150 (CVE-2026-6786)
  * firefox: thunderbird: Incorrect boundary conditions in the WebRTC component (CVE-2026-6753)
  * firefox: thunderbird: Use-after-free in the Widget: Cocoa component (CVE-2026-6759)
  * firefox: thunderbird: Use-after-free in the WebRTC component (CVE-2026-6747)
  * firefox: thunderbird: Information disclosure due to uninitialized memory in the Graphics: Canvas2D component (CVE-2026-6749)
  * firefox: thunderbird: Incorrect boundary conditions in the Libraries component in NSS (CVE-2026-6766)
  * firefox: thunderbird: Privilege escalation in the Networking component (CVE-2026-6761)
  * firefox: thunderbird: Mitigation bypass in the File Handling component (CVE-2026-6763)
  * firefox: thunderbird: Privilege escalation in the Graphics: WebRender component (CVE-2026-6750)
  * firefox: thunderbird: Uninitialized memory in the Audio/Video: Web Codecs component (CVE-2026-6748)
  * firefox: thunderbird: Memory safety bugs fixed in Firefox ESR 115.35, Firefox ESR 140.10, Thunderbird ESR 140.10, Firefox 150 and Thunderbird 150 (CVE-2026-6785)
  * firefox: thunderbird: Mitigation bypass in the DOM: Security component (CVE-2026-6771)
  * firefox: thunderbird: Incorrect boundary conditions in the DOM: Device Interfaces component (CVE-2026-6764)
  * firefox: thunderbird: Information disclosure in the Form Autofill component (CVE-2026-6765)
  * firefox: thunderbird: Privilege escalation in the Debugger component (CVE-2026-6769)
  * firefox: thunderbird: Uninitialized memory in the Audio/Video: Web Codecs component (CVE-2026-6751)
  * firefox: thunderbird: Incorrect boundary conditions in the WebRTC: Networking component (CVE-2026-6776)
  * firefox: thunderbird: Use-after-free in the DOM: Core & HTML component (CVE-2026-6746)


For more details about the security issue(s), including the impact, a CVSS score, acknowledgments, and other related information, refer to the CVE page(s) listed in the References section.

Häufig gestellte Fragen

What is ALSA-2026:13537?

It is AlmaLinux's Thunderbird erratum for AlmaLinux 8, fixing 25 CVEs (CVE-2026-6746 through CVE-2026-6786) including NSS boundary-condition flaws, JavaScript Engine use-after-free, and DOM spoofing issues shared with Firefox.

Who is affected?

AlmaLinux 8 desktops and workstations running Thunderbird for mail — the flaws are triggered by rendering malicious email content, so any mail client user is in scope.

How do I apply the fix?

Run dnf update thunderbird and restart Thunderbird. Verify with the client's About dialog reporting the updated version.

Is this batch related to Firefox fixes?

Yes — the CVE descriptions carry the 'firefox: thunderbird:' prefix because Mozilla ships shared engine fixes to both products; the AlmaLinux erratum packages them for Thunderbird separately.

Referenzen

Sicherheitshinweise

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