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CVE-2026-54741— Lemmy: Blocked users can edit private messages sent before the block

Quick assessment

Affected
LemmyNet lemmy
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

LemmyNet lemmy是LemmyNet组织的一个去中心化的链接聚合与讨论社区平台。 LemmyNet lemmy 0.19.19之前版本和1.0.0-alpha.18之前版本存在授权问题漏洞，该漏洞源于编辑私信路径未正确检查接收者阻止列表，导致被阻止的发件人可以继续修改旧消息，造成阻止后的骚扰。

CVSS 5.3 · Medium EPSS 0.35% · P29

Possible ATT&CK Techniques 1 AI

T1530 · Data from Cloud Storage

Affected Version Matrix 2

VendorProduct Version RangeStatus
LemmyNet lemmy < 0.19.19 affected
>= 1.0.0-alpha.0, < 1.0.0-alpha.18 affected
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I. Basic Information for CVE-2026-54741

Vulnerability Information
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Vulnerability Title
Lemmy: Blocked users can edit private messages sent before the block
Source: CVE Program / CVE List V5
Vulnerability Description
Lemmy is a link aggregator and forum for the fediverse. Prior to 0.19.19 and 1.0.0-alpha.18, Lemmy blocks new private messages from a sender after the recipient blocks that sender, but the edit path skips the same block check. create_private_message checks the recipient's block list with PersonActions::read_block before inserting a message, while edit_private_message in crates/api/api_crud/src/private_message/update.rs only checks that the caller is orig_private_message.creator_id. The update then writes new content and returns the modified PrivateMessageView without consulting the recipient's block list, allowing a blocked sender to keep changing an old message that the recipient can still see and providing a post-block harassment path. This issue is fixed in versions 0.19.19 and 1.0.0-alpha.18.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N
Source: CVE Program / CVE List V5
Vulnerability Type
授权机制缺失
Source: CVE Program / CVE List V5
Vulnerability Title
LemmyNet lemmy 授权问题漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
LemmyNet lemmy是LemmyNet组织的一个去中心化的链接聚合与讨论社区平台。 LemmyNet lemmy 0.19.19之前版本和1.0.0-alpha.18之前版本存在授权问题漏洞，该漏洞源于编辑私信路径未正确检查接收者阻止列表，导致被阻止的发件人可以继续修改旧消息，造成阻止后的骚扰。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
LemmyNet lemmy < 0.19.19 -

II. Public POCs for CVE-2026-54741

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III. Intelligence Information for CVE-2026-54741

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Patches & Fixes for CVE-2026-54741 (4)

Vendor Advisories for CVE-2026-54741 (1)

Vendor Pages for CVE-2026-54741 (2)

Same Patch Batch · LemmyNet · 2026-08-19 · 6 CVEs total

CVE-2026-54739 6.9 MEDIUM Lemmy: Login Endpoint User Enumeration via HTTP Response Code Differential
CVE-2026-54740 6.5 MEDIUM Lemmy: Lower-ranked federated moderator can remove higher-ranked moderators
CVE-2026-54738 6.5 MEDIUM Lemmy: Rate limit bypass via X-Forwarded-For header spoofing in actix-web ConnectionInfo
CVE-2026-54743 6.4 MEDIUM Lemmy: Stored XSS via markdown image alt-text in lemmy-ui html5-embed
CVE-2026-54742 5.1 MEDIUM Lemmy: `CollectionAdd::Featured` does not check the post is in the community

IV. Related Vulnerabilities

Same product: lemmy
Same vendor: LemmyNet
Same weakness: CWE-862

V. Comments for CVE-2026-54741

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