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

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

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 · score source

EPSS

• CVE-2026-77403: 0.52% estimated exploitation activity in the next 30 days; percentile 44.47 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

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,…

Published by the source

17 Sep 2026, 17:03 UTC

Last modified by the source

1 Oct 2026, 20:45 UTC

Source last checked

26 Oct 2026, 15:29 UTC

1. Revision 4 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-xwwf-m8fg-p9q2

2. Revision 3 · amended · 25 Oct 2026

   Reviewed OSV alias/range/CVSS4 correction; package source scopes and original publication preserved. No customer finding resolved.

3. Revision 2 · amended · 24 Oct 2026

   Amended from osv record GO-2026-6503

4. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-xwwf-m8fg-p9q2

Preview the exact text before you copy it. Commands are read-only suggestions; review them before running anything.

# Patch Next advisory brief: CVE-2026-77403

Advisory: RabbitMQ amqp091-go: Denial of Service via Sub-Spec Frame Size Negotiation
IDs: CVE-2026-77403, GHSA-xwwf-m8fg-p9q2
Record: https://patchnext.com/advisories/cve-2026-77403 (revision 4, source checked 26 Oct 2026, 15:29 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 8.9)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: github.com/rabbitmq/amqp091-go 1.13.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go github.com/rabbitmq/amqp091-go: affected < 1.13.0; fixed in 1.13.0

## Suggested inspection (read-only)
- Go github.com/rabbitmq/amqp091-go: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on github.com/rabbitmq/amqp091-go.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-xwwf-m8fg-p9q2 (OSV record GHSA-xwwf-m8fg-p9q2 lists affected ranges: Go github.com/rabbitmq/amqp091-go >=0 <1.13.0 (fixed))
- Verified: https://osv.dev/vulnerability/GO-2026-6503 (OSV record GO-2026-6503 lists affected ranges: Go github.com/rabbitmq/amqp091-go >=0 <1.13.0 (fixed))
- Verified: https://github.com/advisories/GHSA-xwwf-m8fg-p9q2 (GitHub-reviewed advisory GHSA-xwwf-m8fg-p9q2 lists affected ranges: Go github.com/rabbitmq/amqp091-go >=0 <1.13.0)

Commands are suggestions: review each one before running it.