CVE-2024-23649VulnerabilityPublished 24 Jan 2024Updated 30 May 2025

CVE-2024-23649: LemmyNet lemmy · Improper Authorization

Affects LemmyNet lemmySource CVE Database V5

Not known to be exploited · CVSS 7.5 High : upgrade to 0.19.1 soon.

Data as of 25 Oct 2026, 19:02 UTC

CVSS 3.1 base score

7.5High

How severe the flaw is on the 0–10 CVSS scale.

EPSS: 0.5% chance of exploitation in 30 days – higher than 42% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 0.19.1

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

Attack Vector: Network
Attack Complexity: Low
Privileges Required: None
User Interaction: None
Scope: Unchanged
Confidentiality: High
Integrity: None
Availability: None

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, up to and including the entire Internet. Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files to carry out an attack.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
Scope: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: High: There is total loss of confidentiality, resulting in all resources within the impacted component being divulged to the attacker. Alternatively, access to only some restricted information is obtained, but the disclosed information presents a direct, serious impact.
Integrity: None: There is no loss of integrity within the impacted component.
Availability: None: There is no impact to availability within the impacted component.

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 24 Jan 2024
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 2026-10-25.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Upgrade lemmynet/lemmy to 0.19.1.

Affected software

Product	Affected	Fixed in
GitHublemmynet/lemmy`pkg:github/lemmynet/lemmy`Other threats	Affected >=0.17.0 <0.19.1	Fixed in 0.19.1

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

The primary mitigation is to upgrade all affected Lemmy instances to version 0.19.1 or later, where the vulnerability is patched. Until an upgrade is feasible, administrators should block the /api/v3/private_message/report endpoint at the reverse proxy or firewall level to prevent exploitation. This will disable the ability to report private messages but will protect against unauthorized data disclosure. It is also recommended to audit user registrations and restrict open registrations if possible, to reduce the risk of attacker account creation. Monitoring logs for unusual activity related to private message reporting or enumeration attempts can help detect exploitation attempts. Organizations should review their instance configurations to enforce strict access controls and consider implementing additional application-layer authorization checks. Finally, informing users about the issue and encouraging cautious sharing of sensitive information until the patch is applied can reduce risk.

Description

Lemmy is a link aggregator and forum for the fediverse. Starting in version 0.17.0 and prior to version 0.19.1, users can report private messages, even when they're neither sender nor recipient of the message. The API response to creating a private message report contains the private message itself, which means any user can just iterate over message ids to (loudly) obtain all private messages of an instance. A user with instance admin privileges can also abuse this if the private message is removed from the response, as they're able to see the resulting reports. Creating a private message report by POSTing to `/api/v3/private_message/report` does not validate whether the reporter is the recipient of the message.lemmy-ui does not allow the sender to report the message; the API method should likely be restricted to accessible to recipients only. The API response when creating a report contains the `private_message_report_view` with all the details of the report, including the private message that has been reported: Any authenticated user can obtain arbitrary (untargeted) private message contents. Privileges required depend on the instance configuration; when registrations are enabled without application system, the privileges required are practically none. When registration applications are required, privileges required could be considered low, but this assessment heavily varies by instance. Version 0.19.1 contains a patch for this issue. A workaround is available. If an update to a fixed Lemmy version is not immediately possible, the API route can be blocked in the reverse proxy. This will prevent anyone from reporting private messages, but it will also prevent exploitation before the update has been applied.

Impact

For European organizations using Lemmy instances—particularly those hosting communities or federated forums—this vulnerability poses a serious risk to user privacy and data confidentiality. Private messages, which may contain sensitive personal or organizational information, can be exposed to unauthorized users, undermining trust in the platform and potentially violating data protection regulations such as the GDPR. The breach of confidentiality could lead to reputational damage, legal liabilities, and loss of user base. Since Lemmy is used in various communities including political, social, and professional groups, exposure of private communications could have broader societal impacts. The ease of exploitation without requiring elevated privileges or user interaction increases the likelihood of abuse. Organizations relying on Lemmy for internal or external communications must consider the risk of data leakage and potential compliance violations. Additionally, administrators could misuse the vulnerability to access private messages, raising insider threat concerns.

Summary

CVE-2024-23649 is a high-severity improper authorization vulnerability (CWE-285) affecting LemmyNet's lemmy software versions from 0.17.0 up to but not including 0.19.1. Lemmy is a federated link aggregator and forum platform used in the fediverse. The vulnerability arises because the API endpoint responsible for reporting private messages (/api/v3/private_message/report) does not properly validate whether the user creating the report is authorized to do so—that is, whether they are the sender or recipient of the private message. Consequently, any authenticated user can submit a report for any private message ID, even if they are unrelated to the conversation. The API response to creating such a report includes the full contents of the private message, effectively allowing unauthorized users to enumerate and access all private messages on the instance by iterating over message IDs. This leads to a significant confidentiality breach (CWE-200). The vulnerability is exacerbated by the fact that some Lemmy instances allow open registrations without application approval, meaning an attacker can easily create an account and exploit this flaw without elevated privileges. Even in instances requiring registration approval, the privilege barrier remains low. Instance administrators can also abuse the flaw to view reports and associated private messages. The vulnerability was patched in version 0.19.1. As an interim mitigation, administrators can block the vulnerable API route at the reverse proxy level, which disables private message reporting but prevents exploitation until the patch is applied. The CVSS v3.1 base score is 7.5 (high), reflecting network exploitability without authentication or user interaction, and a high impact on confidentiality with no impact on integrity or availability.

CWE-285Improper Authorization (opens in a new tab)
Class weaknessLikelihood of exploit: HighOWASP Top 10 A01:2025: Broken Access Control (opens in a new tab)
The product does not perform or incorrectly performs an authorization check when an actor attempts to access a resource or perform an action.
MITRE discourages mapping vulnerabilities to this broad entry; the root cause is usually a more specific weakness.
Architecture and Design
Divide the product into anonymous, normal, privileged, and administrative areas. Reduce the attack surface by carefully mapping roles with data and functionality. Use role-based access control (RBAC) to enforce the roles at the appropriate boundaries.
Architecture and Design
Ensure that you perform access control checks related to your business logic. These checks may be different than the access control checks that you apply to more generic resources such as files, connections, processes, memory, and database records.
Architecture and Design · Libraries or Frameworks
Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.
OWASP Cheat Sheets
Authorization (opens in a new tab)
OWASP ASVS 4.0.3
V8.3.8 (opens in a new tab)
V13.4.2 (opens in a new tab)
V7.2.2 (opens in a new tab)
Attack patterns
Accessing Functionality Not Properly Constrained by ACLs (opens in a new tab)
Cross Zone Scripting (opens in a new tab)
Directory Indexing (opens in a new tab)
Subverting Environment Variable Values (opens in a new tab)
Using Malicious Files (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).
CWE-200Exposure of Sensitive Information to an Unauthorized Actor (opens in a new tab)
Class weaknessLikelihood of exploit: HighCWE Top 25 (2025): #20OWASP Top 10 A01:2025: Broken Access Control (opens in a new tab)
The product exposes sensitive information to an actor that is not explicitly authorized to have access to that information.
MITRE discourages mapping vulnerabilities to this broad entry; the root cause is usually a more specific weakness.
Architecture and Design · Separation of Privilege
Compartmentalize the system to have "safe" areas where trust boundaries can be unambiguously drawn. Do not allow sensitive data to go outside of the trust boundary and always be careful when interfacing with a compartment outside of the safe area.
OWASP Cheat Sheets
Error Handling (opens in a new tab)
Logging (opens in a new tab)
Authorization (opens in a new tab)
OWASP ASVS 4.0.3
V8.3.4 (opens in a new tab)
V14.3.3 (opens in a new tab)
V7.3.3 (opens in a new tab)
Attack patterns
Subverting Environment Variable Values (opens in a new tab)
ICMP Echo Request Ping (opens in a new tab)
TCP SYN Scan (opens in a new tab)
Enumerate Mail Exchange (MX) Records (opens in a new tab)
DNS Zone Transfers (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

Community reviews

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 8 Jul 2025, 19:56 UTC

WeaknessesCWE-285, CWE-200

Technical details

References

Community reviews

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