OAuth2 access token could be sent over an unencrypted connection with Exchange accounts

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-126136
StatePUBLISHED
Assignermozilla
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-11-10 19:21:14 UTC
Updated2026-11-10 21:19:27 UTC
DescriptionFor Exchange accounts using EWS or Microsoft Graph with OAuth2 authentication, Thunderbird sent the OAuth2 access token to the server even when the configured server URL used unencrypted HTTP. An attacker able to observe network traffic could obtain the token and use it to access the user's mailbox until the token expired. An attacker positioned on the network during account setup could cause such a URL to be configured. This vulnerability was fixed in Thunderbird 160 and Thunderbird 153.7.

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Mozilla Thunderbird unaffected 153.7 153.* rpm Not specified
CNA Mozilla Thunderbird unaffected 160 * rpm Not specified

References

ReferenceSourceLinkTags
bugzilla.mozilla.org/show_bug.cgi [email protected] bugzilla.mozilla.org
www.mozilla.org/security/advisories/mfsa2026-128 [email protected] www.mozilla.org
www.mozilla.org/security/advisories/mfsa2026-129 [email protected] www.mozilla.org
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis

Vendor Comments And Credit

Discovery Credit

CNA: Álvaro Chico Martínez (en)

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