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CVE-2026-113868

MEDIUM 5.3

Published 2026-10-20 · Last modified 2026-10-20

When authenticating to a POP3 or SMTP server using NTLM, Thunderbird did not check whether the server's challenge was valid base64. A malicious server could send a challenge that caused Thunderbird to include uninitialized heap memory in its NTLM response, disclosing that memory to the server. A challenge consisting only of base64 padding also caused an out-of-bounds read, crashing Thunderbird. This affected accounts configured to use NTLM or GSSAPI authentication. The uninitialized memory disclosure only affected NTLM. This vulnerability was fixed in Thunderbird 158.0.1 and Thunderbird 153.5.1.

NO EXPLOITATION SIGNALS

No known exploitation, public exploit, or elevated probability at this time. Track for changes.

Exploitation likelihood

0.4%chance of exploitation in 30 days · 37th percentile

○ In CISA KEV ○ Catalogued PoC

Impact if exploited

5.3CVSS 3.1 · MEDIUM

  • ConfidentialityNone
  • IntegrityNone
  • AvailabilityHigh

What an attacker needs

  • ✓Access: Reachable over the network — no local access needed
  • ⚠Privileges: Requires a low-privilege account
  • ✓User interaction: No user interaction needed
  • ⚠Complexity: Needs a race window or specific setup

✓ lowers the bar for an attacker · ⚠ raises it

Proof of concept

No public PoC is currently catalogued.

Search for new PoCs

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Tracked sources are checked daily for recent CVEs, including PoCs published after the original disclosure. A later release appears after a tracked source lists it and a refresh succeeds.

Data snapshot:

Affected

Vendors Mozilla

Products Thunderbird

Weakness (CWE)

  • CWE-125: Out-of-bounds Read

CVSS vector

CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H

References and research data (JSON)

Vendor product assessments

  • thunderbird as a component of Red Hat Enterprise Linux 10 · known affected

    Vendor assessment for this product only.

    pkg:rpm/redhat/thunderbird

    • none available: Fix deferred
    Red Hat · CVE-2026-113868 · Updated 2026-10-20T20:08:59+00:00
  • thunderbird.src as a component of Red Hat Enterprise Linux 10 · known affected

    Vendor assessment for this product only.

    pkg:rpm/redhat/thunderbird?arch=src

    • none available: Fix deferred
    Red Hat · CVE-2026-113868 · Updated 2026-10-20T20:08:59+00:00
  • thunderbird as a component of Red Hat Enterprise Linux 8 · known affected

    Vendor assessment for this product only.

    pkg:rpm/redhat/thunderbird

    • none available: Fix deferred
    Red Hat · CVE-2026-113868 · Updated 2026-10-20T20:08:59+00:00
  • thunderbird.src as a component of Red Hat Enterprise Linux 8 · known affected

    Vendor assessment for this product only.

    pkg:rpm/redhat/thunderbird?arch=src

    • none available: Fix deferred
    Red Hat · CVE-2026-113868 · Updated 2026-10-20T20:08:59+00:00
  • thunderbird as a component of Red Hat Enterprise Linux 9 · known affected

    Vendor assessment for this product only.

    pkg:rpm/redhat/thunderbird

    • none available: Fix deferred
    Red Hat · CVE-2026-113868 · Updated 2026-10-20T20:08:59+00:00
  • thunderbird.src as a component of Red Hat Enterprise Linux 9 · known affected

    Vendor assessment for this product only.

    pkg:rpm/redhat/thunderbird?arch=src

    • none available: Fix deferred
    Red Hat · CVE-2026-113868 · Updated 2026-10-20T20:08:59+00:00

All CVSS metrics

  • MEDIUM 5.3 v3.1 · ADP Primary
    CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H
  • MEDIUM 5.3 v3.1 · NVD Secondary
    CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H

References

Advisories

Technical & other

Sources: NVD · CVE.org · EPSS