CVE-2020-6795Public exploitNetwork attack vector

Client crash via repeated finalized MIME processing

Published Mar 2, 2020 · Updated Aug 4, 2024

NULL pointer dereference in Thunderbird before 68.5 allows remote attackers to crash the client via a message containing multiple S/MIME signatures. MimeMultipartSigned_emit_child processes the same MIME object twice, and MimeObject_write later dereferences its cleared state pointer. Opening the crafted message is required; the resulting availability impact is limited to an unexploitable client crash.

CVSS severity6.5
Medium
EPSS probability1.31%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

NULL pointer dereference in Thunderbird before 68.5 allows remote attackers to crash the client via a message containing multiple S/MIME signatures. MimeMultipartSigned_emit_child processes the same MIME object twice, and MimeObject_write later dereferences its cleared state pointer. Opening the crafted message is required; the resulting availability impact is limited to an unexploitable client crash.

The record

CVE
CVE-2020-6795
Published
Mar 2, 2020
Updated
Aug 4, 2024
Vendor
Mozilla
Product
Thunderbird
Classifications
CWE-476, T1204.002
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Mar 2, 2020CVE publishedPublication date reported by the CVE source.
  2. Aug 4, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=unspecified <68.5

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Mozilla · Thunderbirdversion=unspecified <68.5

Published CVSS scores

6.5NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H
4.3NIST NVDAV:N/AC:M/Au:N/C:N/I:N/A:P

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-476NULL Pointer Dereference
T1204.002User Execution: Malicious File

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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