Mastodon up to 4.3.22/4.4.16/4.5.9 Normalization integrity check

Summaryinfo

A vulnerability, which was classified as critical, has been found in Mastodon up to 4.3.22/4.4.16/4.5.9. This vulnerability affects unknown code of the component Normalization Handler. Performing a manipulation results in integrity check. This vulnerability was named CVE-2026-48028. The attack may be initiated remotely. There is no available exploit. It is advisable to upgrade the affected component.

Detailsinfo

A vulnerability classified as critical has been found in Mastodon up to 4.3.22/4.4.16/4.5.9. This affects an unknown functionality of the component Normalization Handler. The manipulation with an unknown input leads to a integrity check vulnerability. CWE is classifying the issue as CWE-354. The product does not validate or incorrectly validates the integrity check values or "checksums" of a message. This may prevent it from detecting if the data has been modified or corrupted in transmission. This is going to have an impact on integrity, and availability. The summary by CVE is:

Mastodon is a free, open-source social network server based on ActivityPub. Prior to 4.5.10, 4.4.17, and 4.3.23, Mastodon's normalization of incoming activities signed with Linked-Data Signatures does not sufficiently protect the activities from a certain class of spoofing, allowing threat actors to remove JSON entries from valid signed activities from a third-party actor. This vulnerability is fixed in 4.5.10, 4.4.17, and 4.3.23.

It is possible to read the advisory at github.com. This vulnerability is uniquely identified as CVE-2026-48028 since 05/20/2026. The exploitability is told to be easy. It is possible to initiate the attack remotely. No form of authentication is needed for exploitation. The technical details are unknown and an exploit is not publicly available.

Upgrading to version 4.3.23, 4.4.17 or 4.5.10 eliminates this vulnerability.

Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.

Productinfo

Name

• Mastodon

Version

• 4.3.0
• 4.3.1
• 4.3.2
• 4.3.3
• 4.3.4
• 4.3.5
• 4.3.6
• 4.3.7
• 4.3.8
• 4.3.9
• 4.3.10
• 4.3.11
• 4.3.12
• 4.3.13
• 4.3.14
• 4.3.15
• 4.3.16
• 4.3.17
• 4.3.18
• 4.3.19
• 4.3.20
• 4.3.21
• 4.3.22
• 4.4.0
• 4.4.1
• 4.4.2
• 4.4.3
• 4.4.4
• 4.4.5
• 4.4.6
• 4.4.7
• 4.4.8
• 4.4.9
• 4.4.10
• 4.4.11
• 4.4.12
• 4.4.13
• 4.4.14
• 4.4.15
• 4.4.16
• 4.5.0
• 4.5.1
• 4.5.2
• 4.5.3
• 4.5.4
• 4.5.5
• 4.5.6
• 4.5.7
• 4.5.8
• 4.5.9

Website

• Product: https://github.com/mastodon/mastodon/

CPE 2.3info

• 🔒
• 🔒
• 🔒

CPE 2.2info

• 🔒
• 🔒
• 🔒

CVSSv4info

CVSSv3info

CVSSv2info

Exploitinginfo

Threat Intelligenceinfo

Countermeasuresinfo

Timelineinfo

Sourcesinfo

Entryinfo

Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.

Discussion