RabbitMQ amqp091-go: Denial of Service via Sub-Spec Frame Size Negotiation

CISA KEV is observed exploitation evidence. FIRST EPSS is a dated prediction of exploitation in the next 30 days. Missing scores are unknown. This collector requests predictions only for explicit CVE aliases in the public NuGet archive; Microsoft release views retain their existing prediction scope.

No collected risk observation for these identifiers. This does not establish absence of exploitation or a zero probability.

RabbitMQ amqp091-go is a Go AMQP 0.9.1 client. Prior to 1.13.0, Connection.openTune in connection.go accepts a server-advertised FrameMax below the AMQP frameMinSize value of 4096 bytes because the connection negotiation loop does not enforce the protocol minimum. A malicious or compromised AMQP broker can therefore advertise an extremely small FrameMax, causing later client publications to be fragmented into excessive numbers of frames and write operations. This can consume CPU and stall the client or its host. This issue is fixed in version 1.13.0.

Source published

16 Sep 2026 14:36:19 UTC

Source modified

16 Sep 2026 15:43:19 UTC

Observed here

23 Oct 2026 15:48:27 UTC

Source terms

CVE Program Terms of Use

Original source record · Cite this exact observation · Complete original publisher JSON

This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: cve-program · CVE Program Terms of Use. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS 4.0 · 8.9 CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:H

RabbitMQ amqp091-go is a Go AMQP 0.9.1 client. Prior to 1.13.0, Connection.openTune in connection.go accepts a server-advertised FrameMax below the AMQP frameMinSize value of 4096 bytes because the connection negotiation loop does not enforce the protocol minimum. A malicious or compromised AMQP broker can therefore advertise an extremely small FrameMax, causing later client publications to be fragmented into excessive numbers of frames and write operations. This can consume CPU and stall the client or its host. This issue is fixed in version 1.13.0.

Source published

Sep 16, 2026, 2:36:19 PM (timezone not stated)

Source modified

Sep 16, 2026, 3:43:19 PM (timezone not stated)

Observed here

11 Nov 2026 16:08:39 UTC

Source terms

ENISA EUVD · source terms and attribution apply

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This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: euvd · ENISA EUVD · source terms and attribution apply. Source text is retained; field grouping and change labels are provided by ChangeIntel.

EUVD CVSS 4.0 · 8.9 CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:H

RabbitMQ amqp091-go is a Go AMQP 0.9.1 client. Prior to 1.13.0, Connection.openTune in connection.go accepts a server-advertised FrameMax below the AMQP frameMinSize value of 4096 bytes because the connection negotiation loop does not enforce the protocol minimum. A malicious or compromised AMQP broker can therefore advertise an extremely small FrameMax, causing later client publications to be fragmented into excessive numbers of frames and write operations. This can consume CPU and stall the client or its host. This issue is fixed in version 1.13.0.

Source published

16 Sep 2026 15:17:46 UTC

Source modified

23 Sep 2026 18:19:19 UTC

Observed here

25 Oct 2026 16:19:04 UTC

Source terms

NIST NVD usage terms; underlying source attribution retained

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This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: nvd · NIST NVD usage terms; underlying source attribution retained. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS 4.0 · [email protected] · Secondary · 8.9 CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:H/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

## Summary A Denial of Service (DoS) vulnerability exists in the AMQP client's connection negotiation logic. The AMQP specification explicitly mandates a strict minimum frame size of 4096 bytes to prevent pathological packet fragmentation. While the library defines a `frameMinSize = 4096` constant, the connection negotiation loop fails to enforce this boundary, blindly accepting whatever maximum frame size (`FrameMax`) the server advertises during the handshake. If a client connects to a malicious or compromised AMQP broker that advertises an extremely low `FrameMax` (such as 1 byte), the negotiation succeeds. Consequently, every subsequent message transmission is forced to splinter into thousands or millions of single-byte frames, causing massive CPU overhead, thread contention, and a near-instantaneous application freeze. --- ## Vulnerability Details ### Mechanism During the connection establishment phase, the client and server negotiate connection parameters—including maximum channel count, heartbeat intervals, and maximum frame sizes. The vulnerability is located where the client accepts the server's tuning parameters: ```go // Connection negotiation logic maps server values directly without validation if serverSettings.FrameMax > 0 { // VULNERABILITY: Lacks a floor validation check against frameMinSize (4096) c.config.FrameMax = serverSettings.FrameMax } ``` Because there is no conditional check asserting that `serverSettings.FrameMax >= frameMinSize`, a value below the protocol specification floor is successfully registered. When the application later passes data payloads to the frame writer, the chunking algorithm splits the payload using the negotiated `FrameMax` value as its chunk window divisor. ### Impact When `FrameMax` is set to an absurdly low threshold (e.g., 1 to 10 bytes): * A standard 10 KiB message payload requires tens of thousands of individual write operations and frame headers. * The system's CPU becomes entirely bound by frame serialization, memory allocation for frame structures, and context switching within the network output loops. * This results in an application-layer Denial of Service (DoS) affecting not just the specific AMQP connection, but potentially the entire host system due to CPU resource starvation. --- ## Attack Vector An attacker who compromises an upstream AMQP broker, performs a Man-in-the-Middle (MitM) interception, or tricks an application into connecting to an unauthorized external rogue broker can trigger this vulnerability: 1. **Rogue Handshake:** The client application connects to an AMQP endpoint controlled by the attacker. 2. **Malicious Parameter Tuning:** During the `connection.tune` phase, the rogue server returns a `FrameMax` value of `1`. 3. **Resource Exhaustion Trigger:** The client completes the handshake successfully. As soon as the client attempts to publish a message or process traffic, the internal loop fragments the data into single-byte frames, spiking the host's CPU usage to 100% and disabling the application thread.

Source published

17 Sep 2026 17:03:50 UTC

Source modified

1 Oct 2026 20:55:38 UTC

Observed here

24 Oct 2026 13:19:41 UTC

Source terms

GitHub Advisory Database · CC-BY-4.0

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This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: osv · GitHub Advisory Database · CC-BY-4.0. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS_V4 · CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:H

Publisher rating · HIGH

RabbitMQ amqp091-go: Denial of Service via Sub-Spec Frame Size Negotiation in github.com/rabbitmq/amqp091-go

Source published

1 Oct 2026 20:23:56 UTC

Source modified

1 Oct 2026 20:45:11 UTC

Observed here

24 Oct 2026 13:19:41 UTC

Source terms

OSV · upstream source license applies

Original source record · Cite this exact observation · Complete original publisher JSON

This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: osv · OSV · upstream source license applies. Source text is retained; field grouping and change labels are provided by ChangeIntel.