- Exploited
- No known exploitation
- Fix
- No fix listed
- Who is exposed
- Not reported
- Last modified
- Whether it needs action now or is a reference record, by fixed rules, with why. Last checked is when cve.now last re-read it.What do these mean? →
- Reference
- Last checked
- A 0-100 score for how much a CVE matters across the industry: exploitation, exposure, how widely the software is used, severity and whether a fix exists.What do these mean? →
- 5/100 · provisional
- Whether working attack code is public (Exploit-DB, Metasploit, Nuclei or GitHub). Public code makes attacks easier.What do these mean? →
- None on Exploit-DB, Metasploit or GitHub
Summary
Thunderbird, the email client, can send an OAuth2 access token for Exchange accounts (using EWS or Microsoft Graph) over an unencrypted HTTP connection. An attacker who can observe network traffic could capture that token and use it to read the user's mailbox until the token expires.
Written by anthropic/claude-haiku-5.5 from the sources below. Verify against them.
Read the original description
For 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.
cve.now Index
- Exploitation?/40Unknown. No CISA SSVC exploitation rating yet
- Exposure?/25Unknown. No advisory context yet
- Reach?/20Unknown. No tracked technology or package matched
- Severity?/10Unknown. No CVSS score or vendor rating
- No patch5/5No patch listed yet
What would change the score
- Would score about 60 if added to CISA KEV
- Would score about 55 if CISA's SSVC rates exploitation active
- Would score about 27 if advisories confirm default setups are exposed
Check your systems with an agent
Paste this into a coding or ops agent. It checks your systems read-only and reports a table per asset.
Check whether my systems are affected by CVE-2026-126136 (OAuth2 access token could be sent over an unencrypted connection with Exchange accounts), using the cve.now data below. Rules: work read-only. Do not run exploit code, proof-of-concept scripts or scanners that send attack payloads, and do not change any configuration, package, image or deployment. Report findings only. What cve.now has for CVE-2026-126136 (entry last updated 2026-11-10): Affected: - Mozilla Thunderbird: version range not reported Fixed versions: none listed yet. Setup: unknown whether the bug needs a non-default feature or setting. Check the advisory. CISA KEV: CVE-2026-126136 is not listed as of cve.now's last read. This KEV status is for CVE-2026-126136 only. If you also check another CVE, look up its own KEV status; never assume it from this one. How to check: - Installed software: check what is actually running, not what a repo declares. Read the version from each host, container image and Kubernetes node (the binary's version output, the OS package database, image layers), and check whether the conditions above hold there. Distribution packages may carry a backported fix under an older version number; confirm against the distribution's own advisory. Verify against the linked advisories before concluding, and cite the date you read each one: - https://bugzilla.mozilla.org/show_bug.cgi?id=2085865 - https://www.mozilla.org/security/advisories/mfsa2026-128/ - https://www.mozilla.org/security/advisories/mfsa2026-129/ Do not conclude an asset is unaffected unless you checked it and the evidence covers both its version and the conditions above. If you could not check something, mark it unknown and say what is missing. Report a table with one row per asset and these columns: Asset | Version or build | Status (affected, fixed, not applicable, unknown) | Compensating controls | Exposure (internet-facing, internal, none) | Evidence | Next action. Entry: https://cve.now/CVE-2026-126136 For follow-up questions, use the cve.now MCP server at https://mcp.cve.now/mcp (no authentication), for example get_vulnerability with id CVE-2026-126136.
Timeline
- CVE published
- Record last updated
- First seen by cve.now
Affected versions
- Mozilla Thunderbird
Version range not reported
Evidence 5
Vendor advisory · 3
Establishes: Affected and fixed versions.
- Link
- Link
- Link
CVE record · 2
Establishes: The identifier and description.
- Record
- Record
Corrections
None so far.
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