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CVE-2026-113868

Uninitialized memory disclosure and out-of-bounds read in POP3 and SMTP NTLM authentication

5.3 MediumFix available

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.

Attack profile

How easy it is to exploit

Attack vector
Network
Complexity
High
Privileges needed
Low
User interaction
None

What an attacker can affect

Confidentiality
None
Integrity
None
Availability
High

Exploit likelihood

0.43%Unchanged since Oct 21, 2026
90%50%10%1%

What each source reports

CVE List Score used 5.3

Uninitialized memory disclosure and out-of-bounds read in POP3 and SMTP NTLM authentication

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.

Record
CVE-2026-113868
CVSS 3.1
5.3 MediumCVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H
Weakness
CWE-125
Updated
2026-11-02
EUVDEUVD-2026-105295 5.3

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.

Record
EUVD-2026-105295
CVSS 3.1
5.3 MediumCVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H
Updated
2026-11-02
GitHub AdvisoriesGHSA-v77j-vmg8-85hq 5.3

When authenticating to a POP3 or SMTP server using NTLM, Thunderbird did not check whether the...

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.

Record
GHSA-v77j-vmg8-85hq
CVSS 3.1
5.3 MediumCVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H
Weakness
CWE-125
Updated
2026-11-02
NVD 5.3

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.

Record
CVE-2026-113868
CVSS 3.1
5.3 MediumCVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H
Weakness
CWE-125
Updated
2026-11-02
OSVDEBIAN-CVE-2026-113868 5.3

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.

Record
DEBIAN-CVE-2026-113868
CVSS 3.1
5.3 MediumCVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H
Updated
2026-11-02
OSVUBUNTU-CVE-2026-113868 5.3

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.

Record
UBUNTU-CVE-2026-113868
CVSS 3.1
5.3 MediumCVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H
Updated
2026-11-02
OSVopenSUSE-SU-2026:12224-1 No score

MozillaThunderbird-153.5.1-1.1 on GA media

These are all security issues fixed in the MozillaThunderbird-153.5.1-1.1 package on the GA media of openSUSE Tumbleweed.

Record
openSUSE-SU-2026:12224-1
Updated
2026-11-02

Affected products

Affected packages

Affected packages
PackageAffectedFixed
thunderbird
Debian:12
before 1:153.5.1esr-1~deb12u1, plus listed versions
1:102.11.0-11:102.12.0-11:102.12.0-1~deb10u11:102.12.0-1~deb11u11:102.12.0-1~deb12u1
Show 45 moreShow less
1:102.13.0-11:102.13.0-1~deb10u11:102.13.0-1~deb11u11:102.13.0-1~deb12u11:102.13.1-11:102.13.1-1~deb10u11:102.13.1-1~deb11u11:102.13.1-1~deb12u11:102.14.0-1~deb10u11:102.14.0-1~deb11u11:102.14.0-1~deb12u11:102.15.0-1~deb10u11:102.15.0-1~deb11u11:102.15.0-1~deb12u11:102.15.1-1~deb10u11:102.15.1-1~deb11u11:102.15.1-1~deb12u11:103.0~b5-11:104.0~b2-11:110.0~b4-11:112.0~b1-11:113.0~b3-11:114.0~b2-11:115.0-11:115.0.1-11:115.0.1-21:115.0~b4-11:115.0~b6-11:115.1.0-11:115.1.1-11:115.10.1-11:115.10.1-1~deb10u11:115.10.1-1~deb11u11:115.10.1-1~deb12u11:115.11.0-11:115.11.0-1~deb10u11:115.11.0-1~deb11u11:115.11.0-1~deb12u11:115.12.0-11:115.12.0-1~deb10u11:115.12.0-1~deb11u11:115.12.0-1~deb12u11:115.13.0-11:115.13.0-1~deb11u11:115.13.0-1~deb12u1
1:153.5.1esr-1~deb12u1
thunderbird
Debian:13
before 1:153.5.1esr-1~deb13u1, plus listed versions
1:128.13.0esr-11:128.14.0esr-11:128.14.0esr-1~deb11u11:128.14.0esr-1~deb12u11:128.14.0esr-1~deb13u1
Show 45 moreShow less
1:129.0~b6-11:130.0~b3-11:132.0~b6-11:135.0-11:136.0-11:137.0-11:138.0-11:140.0.1esr-11:140.1.0esr-11:140.1.1esr-11:140.10.0esr-11:140.10.0esr-1~deb11u11:140.10.0esr-1~deb12u11:140.10.0esr-1~deb13u11:140.10.1esr-11:140.10.1esr-1~deb11u11:140.10.1esr-1~deb12u11:140.10.1esr-1~deb13u11:140.10.2esr-11:140.10.2esr-1~deb11u11:140.10.2esr-1~deb12u11:140.10.2esr-1~deb13u11:140.11.0esr-11:140.11.0esr-1~deb11u11:140.11.0esr-1~deb12u11:140.11.0esr-1~deb13u11:140.12.0esr-11:140.12.0esr-1~deb11u11:140.12.0esr-1~deb12u11:140.12.0esr-1~deb13u11:140.13.0esr-11:140.13.0esr-21:140.13.0esr-2~deb11u11:140.13.0esr-2~deb12u11:140.13.0esr-2~deb13u11:140.14.0esr-11:140.14.0esr-1~deb11u11:140.14.0esr-1~deb12u11:140.14.0esr-1~deb13u11:140.15.0esr-1~deb12u11:140.15.0esr-1~deb13u11:140.16.0esr-1~deb12u11:140.16.0esr-1~deb13u11:140.17.0esr-1~deb12u11:140.17.0esr-1~deb13u1
1:153.5.1esr-1~deb13u1
thunderbird
Debian:14
All versions, plus listed versions
1:128.13.0esr-11:128.14.0esr-11:128.14.0esr-1~deb11u11:128.14.0esr-1~deb12u11:128.14.0esr-1~deb13u1
Show 45 moreShow less
1:129.0~b6-11:130.0~b3-11:132.0~b6-11:135.0-11:136.0-11:137.0-11:138.0-11:140.0.1esr-11:140.1.0esr-11:140.1.1esr-11:140.10.0esr-11:140.10.0esr-1~deb11u11:140.10.0esr-1~deb12u11:140.10.0esr-1~deb13u11:140.10.1esr-11:140.10.1esr-1~deb11u11:140.10.1esr-1~deb12u11:140.10.1esr-1~deb13u11:140.10.2esr-11:140.10.2esr-1~deb11u11:140.10.2esr-1~deb12u11:140.10.2esr-1~deb13u11:140.11.0esr-11:140.11.0esr-1~deb11u11:140.11.0esr-1~deb12u11:140.11.0esr-1~deb13u11:140.12.0esr-11:140.12.0esr-1~deb11u11:140.12.0esr-1~deb12u11:140.12.0esr-1~deb13u11:140.13.0esr-11:140.13.0esr-21:140.13.0esr-2~deb11u11:140.13.0esr-2~deb12u11:140.13.0esr-2~deb13u11:140.14.0esr-11:140.14.0esr-1~deb11u11:140.14.0esr-1~deb12u11:140.14.0esr-1~deb13u11:140.15.0esr-1~deb12u11:140.15.0esr-1~deb13u11:140.16.0esr-1~deb12u11:140.16.0esr-1~deb13u11:140.17.0esr-1~deb12u11:140.17.0esr-1~deb13u1
None known
thunderbird
Ubuntu:22.04:LTS
All versions, plus listed versions
1:91.1.2+build1-0ubuntu11:91.3.0+build2-0ubuntu11:91.3.1+build1-0ubuntu11:91.3.2+build1-0ubuntu11:91.4.0+build1.1-0ubuntu1
Show 34 moreShow less
1:91.4.0+build2-0ubuntu11:91.5.0+build1-0ubuntu11:91.5.1+build1-0ubuntu11:91.6.1+build1-0ubuntu11:91.7.0+build1-0ubuntu11:91.7.0+build2-0ubuntu11:91.8.0+build2-0ubuntu11:91.9.1+build1-0ubuntu0.22.04.11:91.11.0+build2-0ubuntu0.22.04.11:102.2.2+build1-0ubuntu0.22.04.11:102.4.2+build2-0ubuntu0.22.04.11:102.7.1+build2-0ubuntu0.22.04.11:102.8.0+build2-0ubuntu0.22.04.11:102.9.0+build1-0ubuntu0.22.04.11:102.10.0+build2-0ubuntu0.22.04.11:102.11.0+build1-0ubuntu0.22.04.11:102.13.0+build1-0ubuntu0.22.04.11:102.15.0+build1-0ubuntu0.22.04.11:102.15.1+build1-0ubuntu0.22.04.11:115.3.1+build1-0ubuntu0.22.04.21:115.4.1+build1-0ubuntu0.22.04.11:115.5.0+build1-0ubuntu0.22.04.11:115.6.0+build2-0ubuntu0.22.04.11:115.8.1+build1-0ubuntu0.22.04.11:115.9.0+build1-0ubuntu0.22.04.11:115.10.1+build1-0ubuntu0.22.04.11:115.11.0+build2-0ubuntu0.22.04.11:115.12.0+build3-0ubuntu0.22.04.11:115.13.0+build5-0ubuntu0.22.04.11:115.15.0+build1-0ubuntu0.22.04.11:115.16.0+build2-0ubuntu0.22.04.11:115.18.0+build1-0ubuntu0.22.04.11:128.12.0+build1-0ubuntu0.22.04.11:140.7.1+build1-0ubuntu0.22.04.1
None known
thunderbird
Ubuntu:24.04:LTS
All versions, plus listed versions
1:115.3.1+build1-0ubuntu11:115.4.1+build1-0ubuntu11:115.4.3+build1-0ubuntu11:115.5.0+build1-0ubuntu11:115.5.1+build1-0ubuntu1
Show 9 moreShow less
1:115.5.2+build2-0ubuntu11:115.6.0+build1-0ubuntu11:115.6.0+build2-0ubuntu11:115.6.1+build1-0ubuntu11:115.8.0+build1-0ubuntu11:115.8.1+build1+snap21:115.8.1+build1+snap32:1snap1-0ubuntu12:1snap1-0ubuntu3
None known
thunderbird
Ubuntu:26.10
All versions, plus listed versions
2:1snap1-0ubuntu5
None known
thunderbird
Ubuntu:26.04:LTS
All versions, plus listed versions
2:1snap1-0ubuntu32:1snap1-0ubuntu42:1snap1-0ubuntu5
None known
MozillaThunderbird
openSUSE:Tumbleweed
From an advisory covering 66 CVEs
before 153.5.1-1.1
153.5.1-1.1

History

History
RecordedChangedSources
affected, facts
first indexedCVE List, EUVD, GitHub Advisories, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2026-113868 is a medium vulnerability (CVSS 5.3) in Mozilla Thunderbird, published October 20, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.43%, the 37th percentile. Fixed in thunderbird 1:153.5.1esr-1~deb12u1.

References

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Left out here: 305 versions. The JSON record has them.

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