CVE-2023-36461

Mastodon vulnerable to Denial of Service through slow HTTP responses

HIGH

7.5

CVSS Score

Published: July 6, 2023 at 06:57 PM UTC

Updated: June 17, 2026 at 06:06 AM UTC

2 products affected across 2 vendorsMastodonMastodon

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Severity

HIGH7.5

Exploit prediction

EPSS 1%

SSVC

No known exploit

Description

Mastodon is a free, open-source social network server based on ActivityPub. When performing outgoing HTTP queries, Mastodon sets a timeout on individual read operations. Prior to versions 3.5.9, 4.0.5, and 4.1.3, a malicious server can indefinitely extend the duration of the response through slowloris-type attacks. This vulnerability can be used to keep all Mastodon workers busy for an extended duration of time, leading to the server becoming unresponsive. Versions 3.5.9, 4.0.5, and 4.1.3 contain a patch for this issue.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

Mastodon · Joinmastodon

95%

v < 3.5.94.0.0 ≤ v < 4.0.54.1.0 ≤ v < 4.1.3

Affected range stops below 3.5.9, so it looks safe — our inference, not a vendor statement

Affected range stops below 4.0.5, so it looks safe — our inference, not a vendor statement

Affected range stops below 4.1.3, so it looks safe — our inference, not a vendor statement

Mastodon · Mastodon

60%

v < 3.5.9v < 4.0.5v < 4.1.3

Affected range stops below 3.5.9, so it looks safe — our inference, not a vendor statement

Affected range stops below 4.0.5, so it looks safe — our inference, not a vendor statement

Affected range stops below 4.1.3, so it looks safe — our inference, not a vendor statement

Remediation

No guide yet

No remediation guidance has been written for this CVE yet. What the record does show:

Patch and advisory references

https://github.com/mastodon/mastodon/commit/c5929798bf7e56cc2c79b15bed0c4692ded3dcb6

References (6)

Mailing List

Source: [email protected]

http://www.openwall.com/lists/oss-security/2023/07/06/7

x_refsource_MISCPatchThird Party Advisory

Source: [email protected]

https://github.com/mastodon/mastodon/commit/c5929798bf7e56cc2c79b15bed0c4692ded3dcb6

x_refsource_MISCThird Party Advisory

Source: [email protected]

https://github.com/mastodon/mastodon/releases/tag/v3.5.9

x_refsource_MISCThird Party Advisory

Source: [email protected]

https://github.com/mastodon/mastodon/releases/tag/v4.0.5

x_refsource_MISCThird Party Advisory

Source: [email protected]

https://github.com/mastodon/mastodon/releases/tag/v4.1.3

x_refsource_CONFIRMThird Party Advisory

Source: [email protected]

https://github.com/mastodon/mastodon/security/advisories/GHSA-9pxv-6qvf-pjwc

SSVC — Action Prioritization

SSVCNo known exploitAutomatablePartial impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

7.5HIGHGitHub_M

Attack Vector: NETWORK
Complexity: LOW
Privileges: NONE
User Interaction: NONE
Scope: UNCHANGED
Confidentiality: NONE
Integrity: NONE
Availability: HIGH

Vector?

Quick Info

StatusMODIFIED

CWE

CWE-770

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