Vulnerability · CVE-2026-113866
When setting up an account, Thunderbird's Exchange AutoDiscover lookup also queried the domain's AutoDiscover service over plain HTTP.
Published Oct 20, 2026 · catalog updated Oct 22, 2026 · When setting up an
Check if you run it
No confirmed exploitation is on record for CVE-2026-113866. EPSS is 0.36%. Act only if a listed version of When setting up an is installed.
Gaps on this record
- The stored product name is a package slug. The name on this page is taken from the title (When setting up an).
- No version range is stored. A customer cannot check an installed version against this record.
- No vendor fix or required action is stored. Compare the linked advisory before you change production.
- Severity
- Medium5.9
- Known exploitation
- Not in CISA/VulnCheck KEV
- EPSS
- 0.36%
- Remediation
- Advisory link
- Affected products
- See sources for product scope
When setting up an account, Thunderbird's Exchange AutoDiscover lookup also queried the domain's AutoDiscover service over plain HTTP. Due to a bug, that unencrypted request included the credentials the user had entered, allowing a network attacker to obtain the user's password. This vulnerability was fixed in Thunderbird 158.0.1 and Thunderbird 153.5.1.
No affected version ranges are stored yet. Use the vendor advisory before you decide this record does not apply.
How to fix CVE-2026-113866
Recommended remediation
A patch or advisory reference is linked. Open the original publisher for availability by product version.
Official advisories
What to do
Three questions, each answered from this record only. Confirm the vendor advisory before you patch.
Should you patch?
No confirmed exploitation is on record for CVE-2026-113866. EPSS is 0.36%. Act only if a listed version of When setting up an is installed.
Which versions are affected?
Affected version ranges are not on this record. Compare the installed version with the linked vendor advisory before you change production.
What should an analyst verify?
CWE-523. EPSS 0.36%. There is no CISA KEV listing. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.
Code
The project this record applies to. Exploit listings stay in References.
No public source repository is identified for this product.
Timeline
Detection, updates, and resolution for this record.
Oct 20, 2026 · NIST NVD
Detected
When setting up an account, Thunderbird's Exchange AutoDiscover lookup also queried the domain's AutoDiscover service over plain HTTP. Due to a bug, that unencrypted request included the credentials the user had entered, allowing a network attacker to obtain the user's password. This vulnerability was fixed in Thunderbird 158.0.1 and Thunderbird 153.5.1.
Oct 22, 2026 · NIST NVD
Updated
When setting up an account, Thunderbird's Exchange AutoDiscover lookup also queried the domain's AutoDiscover service over plain HTTP. Due to a bug, that unencrypted request included the credentials the user had entered, allowing a network attacker to obtain the user's password. This vulnerability was fixed in Thunderbird 158.0.1 and Thunderbird 153.5.1.
Sources
- BSI CERT-BundGovernment advisoryCVE-2026-113866
Mozilla Produkte (Thunderbird, Firefox ESR und Firefox): Mehrere Schwachstellen
wid.cert-bund.de - CVE.orgVulnerability recordCVE-2026-113866
Official CVE identifier
cve.org - FIRST EPSSExploitation probabilityCVE-2026-113866
30-day exploitation probability 0.36%
first.org - Mozilla Security AdvisoriesVendor advisoryCVE-2026-113866
Security Vulnerabilities fixed in Thunderbird 153.5.1 — Mozilla
mozilla.org - NIST NVDVulnerability recordCVE-2026-113866
When setting up an account, Thunderbird's Exchange AutoDiscover lookup also queried the domain's AutoDiscover service over plain HTTP. Due to a bug, that unencrypted request included the credentials the user had entered, allowing a network attacker to obtain the user's password.
nvd.nist.gov
References
Freshness
Last verified in this catalog Oct 23, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.