Evidence used
- No CISA KEV confirmation is currently recorded.
- A structured source references public exploit or proof-of-concept material.
- EPSS is 0.56% for the current model date.
BlackTreeCVE IntelligenceFull vulnerability report · 2023
CVE-2023-32677High confidence
Users who can send invitations can erroneously add users to streams during invitation in Zulip
zulip · zulip
Official source article: GitHub GHSA-MRVP-96Q6-JPVC ↗. Check the applicable product and release in the original source.
3.1LowCVSS 3.1
Within 7 days
Patch availableLow technical severity with public exploit material referenced by a structured source; prioritise exposed affected systems while verifying vendor guidance.
R
Open reassessment dashboard →Operational reassessment
Published severity in operational context
Published severityLow→Operational priority:Medium, raised one band.upgradedsince 12 Feb 2025
Compensating controls
- Validate the affected product branch and deploy the verified fixed release.
- Restrict the affected network interface to trusted sources where business-safe.
- Increase monitoring for the attack path and post-exploitation behaviour described in the report.
Verification
- Confirm that the asset runs zulip zulip and falls inside the recorded affected range.
- Verify the installed build against the product-specific fixed version after deployment.
- Validate exposure, authentication requirements and compensating controls in the actual environment.
- Reopen this reassessment when CVSS, KEV, EPSS, exploit evidence or remediation changes.
Low technical severity with public exploit material referenced by a structured source; prioritise exposed affected systems while verifying vendor guidance.
Patch available01
What, why and how
Zulip is an open-source team collaboration tool with unique topic-based threading. Zulip administrators can configure Zulip to limit who can add users to streams, and separately to limit who can invite users to the organization. In Zulip Server 6.1 and below, the UI which allows a user to invite a new user also allows them to set the streams that the new user is invited to -- even if the inviting user would not have permissions to add an existing user to streams. While such a configuration is likely rare in practice, the behavior does violate security-related controls. This does not let a user invite new users to streams they cannot see, or would not be able to add users to if they had that general permission. This issue has been addressed in version 6.2. Users are advised to upgrade. Users unable to upgrade may limit sending of invitations down to users who also have the permission to add users to streams.
What
Zulip is an open-source team collaboration tool with unique topic-based threading. Zulip administrators can configure Zulip to limit who can add users to streams, and separately to limit who can invite users to the organization. In Zulip Server 6.1 and below, the UI which allows a user to invite a new user also allows them to set the streams that the new user is invited to -- even if the inviting user would not have permissions to add an existing user to streams. While such a configuration is likely rare in practice, the behavior does violate security-related controls. This does not let a user invite new users to streams they cannot see, or would not be able to add users to if they had that general permission. This issue has been addressed in version 6.2. Users are advised to upgrade. Users unable to upgrade may limit sending of invitations down to users who also have the permission to add users to streams.
Why
The application reaches a protected operation without first confirming that the requester is authorised.
How
An attacker operating through a network path may attempt exploitation with low privileges. If successful, the issue may cause the confidentiality, integrity or availability impact described by the vendor.
What
Zulip is an open-source team collaboration tool with unique topic-based threading. Zulip administrators can configure Zulip to limit who can add users to streams, and separately to limit who can invite users to the organization. In Zulip Server 6.1 and below, the UI which allows a user to invite a new user also allows them to set the streams that the new user is invited to -- even if the inviting user would not have permissions to add an existing user to streams. While such a configuration is likely rare in practice, the behavior does violate security-related controls. This does not let a user invite new users to streams they cannot see, or would not be able to add users to if they had that general permission. This issue has been addressed in version 6.2. Users are advised to upgrade. Users unable to upgrade may limit sending of invitations down to users who also have the permission to add users to streams.
Why
The application reaches a protected operation without first confirming that the requester is authorised.
How
An attacker operating through a network path may attempt exploitation with low privileges. If successful, the issue may cause the confidentiality, integrity or availability impact described by the vendor.
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 Reference recorded
?
Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.CISA Vulnrichment records proof-of-concept exploitation in its SSVC data. BlackTree has not independently executed or validated exploit material.
- Likely attack path
- a network path → Missing Authorization → cause the confidentiality, integrity or availability impact described by the vendor
- Attack surface
- Network
- Privileges required
- Low: a basic authenticated account is required
- 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-862 ↗
CWE-862: Missing Authorization. The product does not perform 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:L/UI:N/S:U/C:L/I:N/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.PRLowPrivileges required: The attacker needs basic user-level privileges.UINoneUser interaction: No action by another user is required.SUnchangedScope: The security impact remains within the vulnerable component's authority.CLowConfidentiality impact: A successful attack can cause a limited loss.INoneIntegrity impact: No direct loss is represented by this metric.ANoneAvailability impact: No direct loss is represented by this metric.- Post-exploitation / living off the land
- No specific living-off-the-land technique is confirmed in the structured sources. Monitor normal administration tools for activity inconsistent with the affected service's baseline.
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. - Patch available
- Affected
- zulip: > 1.9.0, < 6.2
- Fixed
- 6.2.
- Action
- Review the linked authoritative reference and apply the recorded fixed release appropriate to the affected product branch.
- Workaround
- No verified workaround is recorded. If business-safe, reduce exposure to the affected interface and allow only trusted sources until authoritative guidance is available.
04
Evidence and provenance
Published 19 May 2023 · Last source change 12 Feb 2025, 16:37 UTC · CWE-862 · Missing 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-2023-36918
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
Fixed release or patch 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.