Evidence used
- No CISA KEV confirmation is currently recorded.
- The selected CVSS metric records a network-reachable, unauthenticated path with no user interaction.
- EPSS is 0.90% for the current model date.
BlackTreeCVE IntelligenceFull vulnerability report · 2021
CVE-2021-41100High confidence
Account takeover when having only access to a user's short lived token in wire-server
wireapp · wire-server
Official source article: GitHub GHSA-9RM2-W6PQ-333M ↗. Check the applicable product and release in the original source.
7.4HighCVSS 3.1
Within 7 days
Mitigation availableHigh technical severity; prioritise exposed affected systems while verifying vendor guidance.
R
Open reassessment dashboard →Operational reassessment
Published severity in operational context
Published severityHigh→Operational priority:High, unchanged from published severity.unchanged
Compensating controls
- Apply the linked authoritative mitigation while planning the permanent fix.
- Restrict the affected network interface to trusted sources where business-safe.
- Monitor vendor guidance and exploitation sources for a material change.
Verification
- Confirm that the asset runs wireapp wire-server and falls inside the recorded affected range.
- Recheck the vendor advisory before scheduling a change because no verified fixed version is currently retained.
- Validate exposure, authentication requirements and compensating controls in the actual environment.
- Reopen this reassessment when CVSS, KEV, EPSS, exploit evidence or remediation changes.
High technical severity; prioritise exposed affected systems while verifying vendor guidance.
Mitigation available01
What, why and how
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.
What
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.
Why
The product does not perform or incorrectly performs an authorization check when an actor attempts to access a resource or perform an action.
How
An attacker operating through a network path may attempt exploitation without authentication or user interaction. If successful, the issue may gain additional privileges.
What
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.
Why
The product does not perform or incorrectly performs an authorization check when an actor attempts to access a resource or perform an action.
How
An attacker operating through a network path may attempt exploitation without authentication or user interaction. If successful, the issue may gain additional privileges.
02
Exploit reality and attack path
CVSS severity, EPSS forecast probability, public exploit material and CISA-confirmed exploitation are separate signals.
Observed exploitation No confirmed evidence
?
Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.No CISA KEV match was present at the last successful refresh. This means no confirmation from that source, not proof of no exploitation.
Public PoC / exploit material None recorded
?
Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.No exploit-tagged reference or CISA SSVC proof-of-concept state is currently recorded. Research may still exist outside the structured feeds.
- Likely attack path
- a network path → Improper Authorization → gain additional privileges
- Attack surface
- Network
- Privileges required
- None: unauthenticated exploitation is possible
- User interaction
- None
- Attack complexity
- High: exploitation depends on specific conditions
- Security boundary
- Unchanged: impact remains within the vulnerable component's security authority
- Weakness
?
CWE means Common Weakness Enumeration: a standard category for the underlying weakness. - CWE-285 ↗
CWE-285: Improper Authorization. The product does not perform or incorrectly performs an authorization check when an actor attempts to access a resource or perform an action.
- CVSS vector
?
CVSS means Common Vulnerability Scoring System. The vector records the metric values used to calculate technical severity. CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:NCommon Vulnerability Scoring System 3.1: the compact vector below is decoded into plain language.
AVNetworkAttack vector: The vulnerable component can be reached over a network.ACHighAttack complexity: Successful exploitation depends on specific conditions outside the attacker's direct control.PRNonePrivileges required: The attacker does not need an account or existing privileges.UINoneUser interaction: No action by another user is required.SUnchangedScope: The security impact remains within the vulnerable component's authority.CHighConfidentiality impact: A successful attack can cause a major loss.IHighIntegrity impact: A successful attack can cause a major loss.ANoneAvailability impact: No direct loss is represented by this metric.- Post-exploitation / living off the land
- Stolen credentials, tokens and legitimate administration functions may provide continued access without deploying a large custom toolset.
03
Patch and workaround
Operational remediation based on structured source evidence.
- Status
?
Patch availability is based on structured fixed-version fields and authoritative update references. If no fix is verified, check the vendor advisory before making a change. - Mitigation available
- Affected
- wire-server: < 2021-08-16
- Action
- Apply the mitigation in the linked authoritative guidance while planning the vendor's permanent fix.
- Workaround
- A mitigation or workaround reference is available from the source linked below; validate it against the affected product and version.
04
Evidence and provenance
Published 4 Oct 2021 · Last source change 4 Aug 2024, 02:59 UTC · CWE-285 · Improper Authorization
CVE recordCVE.org · 5.1
CVSS sourceCNA
EPSS source FIRST · tracked since 2026-08-14
?
The date BlackTree first stored a score for this CVE from the daily FIRST EPSS feed.European sourceENISA EUVD · EUVD-2021-28239
Product sourceCNA
Remediation sourceCVE/CNA references
CWE sourceCNA
NVD statusNVD modified after enrichment
Core structured fields are present and their contributing authorities are shown above.
Material change intelligence
View recent updates ↗What changed after publication
No material field changes have been recorded since change tracking began. Routine source refreshes and cosmetic edits are intentionally excluded.
CVE published
Mitigation reference recorded
Technical terms and abbreviations used in this report
- CVE
- Common Vulnerabilities and Exposures: the public identifier for one disclosed vulnerability.
- CVSS
- Common Vulnerability Scoring System: a technical severity framework; it is not patching priority by itself.
- EPSS
- Exploit Prediction Scoring System: FIRST's estimate of the probability that exploitation activity will be observed in the next 30 days; it is a forecast, not confirmation.
- CWE
- Common Weakness Enumeration: the standard category describing the underlying software or hardware weakness.
- CNA
- CVE Numbering Authority: an organisation authorised to assign and publish CVE records.
- CISA ADP
- Cybersecurity and Infrastructure Security Agency Authorized Data Publisher: structured enrichment added to a CVE record.
- NVD
- National Vulnerability Database: NIST's enrichment service for CVE records.
- CERT / CSIRT
- A computer security incident response team that publishes warnings or coordinates incident response.
- PoC
- Proof of concept: public material that demonstrates or helps reproduce exploitation.
- CSAF
- Common Security Advisory Framework: a machine-readable format for security advisories.
- LoTL
- Living off the land: abuse of legitimate tools or system functions during an attack.