CVE-2026-54741Public exploitNetwork attack vector

Post-block message tampering via missing block check

Published Aug 19, 2026 · Updated Aug 20, 2026

Missing authorization in Lemmy before 0.19.19 and 1.0.0-alpha.18 lets remote authenticated users edit pre-block private messages. In crates/api/api_crud/src/private_message/update.rs, edit_private_message verifies only orig_private_message.creator_id and then updates message content without the recipient block check used by create_private_message. Exploitation requires an account that sent the original message before the recipient blocked it, and the effect is limited to changing messages the recipient can still view rather than sending new ones.

CVSS severity5.3
Medium
EPSS probability0.45%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Missing authorization in Lemmy before 0.19.19 and 1.0.0-alpha.18 lets remote authenticated users edit pre-block private messages. In crates/api/api_crud/src/private_message/update.rs, edit_private_message verifies only orig_private_message.creator_id and then updates message content without the recipient block check used by create_private_message. Exploitation requires an account that sent the original message before the recipient blocked it, and the effect is limited to changing messages the recipient can still view rather than sending new ones.

The record

CVE
CVE-2026-54741
Published
Aug 19, 2026
Updated
Aug 20, 2026
Vendor
LemmyNet
Product
Lemmy
Classifications
CWE-862, T1565.001
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Aug 19, 2026CVE publishedPublication date reported by the CVE source.
  2. Aug 20, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 0.19.19
  2. Affected versionversion=>= 1.0.0-alpha.0, < 1.0.0-alpha.18

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

LemmyNet · Lemmyversion=< 0.19.19; version=>= 1.0.0-alpha.0, < 1.0.0-alpha.18

Published CVSS scores

5.3GitHub, Inc.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

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-862Missing Authorization
T1565.001Stored Data Manipulation

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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