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CVE-2026-92240

CRITICAL 9.1 ALL-YEARS

Published 2026-09-15 · Last modified 2026-09-22 · mozilla · NVD: Analyzed

A malicious or compromised IMAP server can trigger an out-of-bounds read in the IMAP response parser by sending an untagged '* ID' response, crashing Thunderbird. The affected parsing path is reachable before authentication. This vulnerability was fixed in Thunderbird 156, Thunderbird 140.16, and Thunderbird 153.3.

ELEVATED IMPACT

Severe if exploited (CVSS 9.1), but no confirmed exploitation. Patch on a normal cadence.

Exploitation likelihood

0.6%chance of exploitation in 30 days · 49th percentile

○ In CISA KEV○ Public exploit / PoC◆ SSVC: exploitation none, automatable yes

Impact if exploited

9.1CVSS 3.1 · CRITICAL · ADP

  • ConfidentialityHigh
  • IntegrityNone
  • AvailabilityHigh

What an attacker needs

  • ✓Access: Reachable over the network — no local access needed
  • ✓Privileges: No account or privileges required
  • ✓User interaction: No user interaction needed
  • ✓Complexity: No special conditions — reliably repeatable

✓ lowers the bar for an attacker · ⚠ raises it

Proof of concept & exploit code

No public exploit or proof-of-concept code is catalogued for this CVE (no ExploitDB, Nuclei, or CISA-KEV entry). It may still exist — search GitHub or check the references below.

Affected

Vendors Mozilla

Products Thunderbird

Weakness (CWE)

  • CWE-125: Out-of-bounds Read

CVSS vector

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

Known Affected Software Configurations

VendorProductVersion range
MozillaThunderbird< 140.16.0
MozillaThunderbird≥ 141.0 and < 153.3.0
MozillaThunderbird≥ 154.0 and < 156.0

All CVSS metrics

  • CRITICAL 9.1 v3.1 · ADP Primary
    CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H
  • CRITICAL 9.1 v3.1 · NVD Secondary
    CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:H

References

Advisories

Technical & other

Sources: NVD · CVE.org · EPSS