CVE-2026-77408: RabbitMQ amqp091-go: Silent Data Truncation and State Corruption via Shortstr Integer Overflow

Should you act?

Critical and remotely reachable

No known exploitation yet, but it is network-reachable without credentials. This signal is computed from CISA KEV, EPSS and CVSS data; it is not an editorial verdict.

• No confirmed exploitation. It is not in CISA’s KEV catalog and CISA’s SSVC assessment records no known exploitation. That can change quickly after a public write-up; re-check if you are affected.
• EPSS 0.5%, percentile 44: FIRST’s model estimates a 0.5% chance of exploitation activity in the next 30 days, higher than 44% of all scored CVEs (low). EPSS is a probability, not a verdict.
• Remotely reachable with no login and no user interaction. If the vulnerable service is exposed to the internet, prioritize it.
• Only applies if your dependency tree includes github.com/rabbitmq/amqp091-go (Go) < 1.13.0, fixed in 1.13.0. Check your lockfile, including transitive dependencies.

What it is

RabbitMQ amqp091-go is a Go AMQP 0.9.1 client. Prior to 1.13.0, the writeShortstr function in write.go casts the byte length of AMQP shortstr property values to uint8 without first rejecting values longer than 255 bytes. An application that accepts an oversized CorrelationId, ReplyTo, MessageId, Expiration, UserId, AppId, ContentType, ContentEncoding, or Type value can therefore serialize a wrapped length and only a truncated prefix, while reporting no error. The resulting silent metadata corruption can break request and reply correlation, routing, tracing, and downstream message processing. This issue is fixed in version 1.13.0.

From the GitHub advisory

Summary A data integrity and protocol corruption vulnerability exists in the AMQP client's property serialization logic. When encoding AMQP short string (shortstr) fields—such as identifiers, routing strings, and content metadata—the length of the string is explicitly cast to a fixed-size 8-bit unsigned integer (uint8).

If an application provides a property string exceeding 255 bytes, the length counter silently wraps around (e.g., a length of 300 wraps to 44). As a result, the parser writes only a truncated portion of the string into the outgoing connection buffer without returning an error. This leads to silent data corruption, broken RPC routing, and unpredictable broker-side state behavior.

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Vulnerability Details

Mechanism The vulnerability resides in the wire-level serialization logic for application publishing properties:

Weakness type: CWE-190.

Product: github.com/rabbitmq/amqp091-go (Go) · Assigned by: GitHub_M · Published: 2026-09-16

Affected and fixed versions

Severity scores

• Attack vector: network (remotely reachable)
• Attack complexity: low
• Attack requirements: present (depends on deployment conditions)
• Privileges required: none (no login)
• User interaction: none

CVSS measures how bad a flaw is if exploited, not how likely exploitation is. Read it next to the exploitation data below.

Exploitation and urgency

• CISA KEV: not listed (no confirmed in-the-wild exploitation known to CISA).
• CISA SSVC assessment: exploitation none, automatable yes, technical impact partial.
• FIRST EPSS (model of 2026-10-21): 0.52% probability of exploitation activity in the next 30 days; percentile 44.

Timeline

• 2026-09-16 — CVE record last updated
• 2026-09-16 — CVE record published by GitHub_M
• 2026-09-17 — GitHub-reviewed advisory GHSA-j497-x9hr-x34x published (critical)

Sources and references

Original sources first. Version and fix details should always be confirmed against the vendor or project advisory.

Vulnerability records

1. GitHub Advisory GHSA-j497-x9hr-x34x github.com
2. CVE.org record CVE-2026-77408 cve.org
3. NVD entry CVE-2026-77408 nvd.nist.gov

Other references from the CVE record and advisory

1. github.com github.com
2. github.com github.com
3. github.com github.com
4. github.com github.com

Critical Go advisories · Today’s Security Digest