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Wire ServerApplication · Wire

CVE-2021-41100

CRITICAL · 9.8 CVSS v3.1 Published 2021-10-04
Fix available
A fix is available. Upgrade to 2021-08-16 or later.
See remediation →
100/100
Remediation priority · Urgent
Remotely reachable No privileges Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
Wire-server is the backing server for the open source wire secure messaging application. In affected versions it is possible to trigger email address change of a user with only the short-lived session token in the `Authorization` header. As the short-lived token is only meant as means of authentication by the client for less critical requests to the backend, the ability to change the email address with a short-lived token constitutes a privilege escalation attack. Since the attacker can change the password after setting the email address to one that they control, changing the email address can result in an account takeover by the attacker. Short-lived tokens can be requested from the backend by Wire clients using the long lived tokens, after which the long lived tokens can be stored securely, for example on the devices key chain. The short lived tokens can then be used to authenticate the client towards the backend for frequently performed actions such as sending and receiving messages. While short-lived tokens should not be available to an attacker per-se, they are used more often and in the shape of an HTTP header, increasing the risk of exposure to an attacker relative to the long-lived tokens, which are stored and transmitted in cookies. If you are running an on-prem instance and provision all users with SCIM, you are not affected by this issue (changing email is blocked for SCIM users). SAML single-sign-on is unaffected by this issue, and behaves identically before and after this update. The reason is that the email address used as SAML NameID is stored in a different location in the databse from the one used to contact the user outside wire. Version 2021-08-16 and later provide a new end-point that requires both the long-lived client cookie and `Authorization` header. The old end-point has been removed. If you are running an on-prem instance with at least some of the users invited or provisioned via SAML SSO and you cannot update then you can block `/self/email` on nginz (or in any other proxies or firewalls you may have set up). You don't need to discriminate by verb: `/self/email` only accepts `PUT` and `DELETE`, and `DELETE` is almost never used.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

Wire-server allows email address changes using only short-lived session tokens in the Authorization header, which should only be used for low-criticality requests. This authorization bypass enables privilege escalation where an attacker can change the email to one they control and then reset the password, achieving account takeover.

MitigationUpdate to version 2021-08-16 or later which requires both the long-lived client cookie AND Authorization header for the email change endpoint, or block the /self/email endpoint at nginz/proxy level as a workaround.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Wire ServerApplication
Affected:< 2021-08-16

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify Wire Server version
    Check the installed version of wire-server by examining the deployed Helm charts, Docker image tags, or the version file in the deployment. Common locations: helm release values, Docker image tags, or /etc/wire-server/version file if present in the container.
    Affected if The version is earlier than 2021-08-16 (e.g., any version from 2021 or earlier releases)
  2. Verify nginz proxy configuration
    Inspect the nginz configuration files in the deployment, typically found in nginz/conf or similar paths in the wire-server deployment. Look for the /self/email endpoint configuration.
    Affected if The /self/email endpoint is not blocked or the configuration does not require both Authorization header AND client cookie for this endpoint
  3. Check API gateway routing
    Review the API gateway or reverse proxy configuration that handles requests to the Brig service (user authentication service). Identify how the /self/email endpoint is routed and what authentication methods are required.
    Affected if The endpoint accepts Authorization header alone without requiring the long-lived session cookie as additional authentication
  4. Test endpoint authorization behavior
    If you have a test environment, send a request to /self/email using only an Authorization header with a short-lived token (e.g., access token) and observe whether the email change is accepted without requiring a session cookie.
    Affected if The email change operation succeeds with Authorization header alone and does not require both the Authorization header AND a client cookie

You are affected if your Wire Server version is earlier than 2021-08-16 AND the /self/email endpoint is accessible without requiring both the short-lived Authorization token AND a long-lived session cookie for email change requests.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Upgrade available Upgrade to 2021-08-16 or later
Fixed in 2021-08-16
Interim mitigation

Update to version 2021-08-16 or later which requires both the long-lived client cookie AND Authorization header for the email change endpoint, or block the /self/email endpoint at nginz/proxy level as a workaround.

Recommended fix High confidence

Version 2021-08-16 or later

  1. Upgrade Wire Server to version 2021-08-16 or later to get the fixed version with the new endpoint requiring both long-lived client cookie and Authorization header
  2. If upgrade is not immediately possible, block the `/self/email` endpoint on nginz (or any other proxies/firewalls) as an alternative mitigation
Caveat The new version requires both the long-lived client cookie and Authorization header for the email change endpoint; the old endpoint has been removed

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Wire Server Scoped from the published advisory
  • Consultation3.0 h
  • Implementation4.0 h
  • Testing3.0 h
  • Review / QA2.0 h
12.0 hours of engineering $2,130
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2021-41100 in production — separate from our analysis above.

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data