CVE-2026-46597: Golang Crypto Buffer Overflow Vulnerability

CVE-2026-46597 Overview

CVE-2026-46597 affects the golang.org/x/crypto module's Secure Shell (SSH) implementation. An incorrectly placed cast from bytes to integer in the AES-GCM packet decoder allows well-crafted inputs to trigger a server-side panic. The flaw maps to [CWE-704: Incorrect Type Conversion or Cast] and impacts services that rely on the affected package for SSH transport encryption. A remote, unauthenticated attacker can send crafted packets to crash the server process, resulting in denial of service.

Critical Impact
Remote, unauthenticated attackers can panic SSH server processes built on golang.org/x/crypto, disrupting availability of any application that uses the package for AES-GCM encrypted transport.

Affected Products

golang.org/x/crypto (Go module)
Applications and services that import the affected crypto package for SSH transport
Server-side SSH implementations using the AES-GCM packet decoder

Discovery Timeline

2026-05-22 - CVE-2026-46597 published to NVD
2026-05-28 - Last updated in NVD database

Technical Details for CVE-2026-46597

Vulnerability Analysis

The vulnerability resides in the AES-GCM packet decoder within the SSH transport layer of the golang.org/x/crypto module. AES-GCM (Advanced Encryption Standard in Galois/Counter Mode) is used to provide authenticated encryption for SSH packets. The decoder reads a length field from incoming ciphertext and uses it to size subsequent buffer operations. Because the cast from byte values to an integer is placed incorrectly in the decoding flow, malformed length values are not validated within their intended numeric domain before being used. A remote attacker who can deliver a crafted packet to the affected decoder triggers a runtime panic in the Go process. The crash terminates the goroutine handling the connection and, depending on the host application, may bring down the entire SSH service. Confidentiality and integrity are not impacted, but availability is fully compromised.

Root Cause

The defect is an incorrect type conversion classified as [CWE-704]. The cast between byte slices and integer types occurs at the wrong stage of packet length validation. Bounds checking that should reject malformed values either does not execute or operates on the wrong representation. Untrusted network input therefore reaches arithmetic and slicing operations that panic.

Attack Vector

The attack is performed over the network with no authentication or user interaction required. An attacker connects to an exposed SSH endpoint that uses the affected golang.org/x/crypto AES-GCM decoder and sends a specially crafted packet. The malformed input forces the decoder into a panic path, terminating the server-side handler. Repeated requests can sustain the denial-of-service condition.

No verified public proof-of-concept code is referenced in the advisory. See the Go.dev Vulnerability Report (GO-2026-5013) and the Go.dev Issue Tracker for upstream technical details.

Detection Methods for CVE-2026-46597

Indicators of Compromise

Unexpected Go runtime panic messages in SSH server logs referencing AES-GCM decoding or golang.org/x/crypto/ssh stack frames
Repeated abrupt termination of SSH worker goroutines or service restarts following inbound connections
Spikes in failed SSH handshakes from a single source followed by service unavailability

Detection Strategies

Inventory Go applications and identify those importing vulnerable versions of golang.org/x/crypto using govulncheck against advisory GO-2026-5013
Monitor process supervisors (systemd, Kubernetes, container runtimes) for crash loops on SSH-facing services written in Go
Correlate SSH connection attempts with subsequent process exits to identify exploitation attempts

Monitoring Recommendations

Forward SSH server stdout/stderr and panic stack traces to a centralized logging pipeline for analysis
Alert on Go panic signatures originating from crypto/ssh packet handling code paths
Track availability metrics and restart counts for SSH and SFTP services exposed to untrusted networks

How to Mitigate CVE-2026-46597

Immediate Actions Required

Identify all binaries embedding golang.org/x/crypto and update to the fixed version referenced in GO-2026-5013
Rebuild and redeploy affected Go applications after upgrading the module dependency
Restrict network exposure of SSH endpoints to trusted source ranges until patching completes

Patch Information

The Go team released a fix referenced in the Go.dev Change Log (CL 781620) and announced via the golang-announce mailing list. Upgrade golang.org/x/crypto to the patched release listed in advisory GO-2026-5013 and rebuild dependent binaries. Vendored copies of the module must also be updated, since Go statically links dependencies into the final executable.

Workarounds

Place affected SSH services behind a network access control list or bastion until patches are applied
Disable AES-GCM cipher suites in the SSH server configuration where feasible, forcing clients to negotiate unaffected ciphers
Apply rate limiting and connection throttling at the network edge to slow repeated exploitation attempts

bash

# Update golang.org/x/crypto to the patched version and verify with govulncheck
go get golang.org/x/crypto@latest
go mod tidy
go install golang.org/x/vuln/cmd/govulncheck@latest
govulncheck ./...