shopsprint/decimal Go Module DNS Backdoor Typosquat

Suspected

Discovered May 24, 2026

The Go module github.com/shopsprint/decimal typosquatted github.com/shopspring/decimal and used an init-time DNS TXT command loop in v1.3.3.

Affected Packages

Observables

Sources

Defender Action Panel

Triage this incident quickly

Check whether your environment installed affected software, copy the top IOCs, run the tested hunting script when available, then review remediation guidance.

Am I affected?: Review affected software below
Immediate action: Audit locks, CI runners, developer workstations, and credential exposure.
Hunting: Has hunting script

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dnslog-cdn-images[.]freemyip[.]com
freemyip[.]com
go[.]mod
go[.]sum
decimal[.]go

Analysis

Executive Summary

Socket reported that github.com/shopsprint/decimal is a long-running one-character typosquat of the legitimate github.com/shopspring/decimal Go module Socket opens in a new tab. GBHackers noted that the module sat clean for years to establish reputation before receiving its weaponized v1.3.3 update GBHackers opens in a new tab. The malicious v1.3.3 release added an init() goroutine that queried DNS TXT records and executed returned commands, giving attackers a stealthy command channel inside any application importing the typoed module, bypassing basic firewall layers Cybersecurity News opens in a new tab.

The source repository and owner were removed by disclosure time, but Go's public module proxy continued to serve the cached module artifact because proxy.golang.org permanently caches published module zips Go Modules opens in a new tab. Defenders must search source, go.mod, go.sum, vendored code, build caches, and released binaries for the typoed module path, replace it with the canonical github.com/shopspring/decimal path, and enforce checksum/proxy hardening guidelines CyberPress opens in a new tab.

Key Facts

Threat Type: Go module typosquat with DNS TXT backdoor

Ecosystem: Go modules

Registry: proxy.golang.org and pkg.go.dev

Affected Packages:

github.com/shopsprint/decimal

Malicious Versions:

v1.3.3

Known Good Versions:

github.com/shopspring/decimal legitimate module path

Fixed Or Safe Versions:

replace typoed path with github.com/shopspring/decimal and rebuild from clean caches

Execution Trigger: Go package init() when imported by a program

Primary Impact: remote command execution through DNS TXT command channel

Campaign Context: Long-lived typosquat disclosed during the May 2026 supply-chain incident wave.

Confidence: high

Canonical Source: https://socket.dev/blog/popular-go-decimal-library-typosquat-dns-backdoor opens in a new tab

Last Verified: 2026-05-24

Evidence Assessment

confirmed: Socket identifies github.com/shopsprint/decimal@v1.3.3 as the malicious Go module version and contrasts it with the legitimate github.com/shopspring/decimal package Socket opens in a new tab.
confirmed: The malicious diff added network, command-execution, and timing imports plus an init() goroutine in decimal.go Socket opens in a new tab.
confirmed: The command channel uses DNS TXT queries to dnslog-cdn-images[.]freemyip[.]com and executes returned content Socket opens in a new tab.
confirmed: Socket states the Go Module Proxy still served the cached malicious v1.3.3 artifact after the GitHub source disappeared Socket opens in a new tab.
unclear: Public reporting does not prove the number of downstream builds or binaries that imported the typoed path.

Impact Determination

Analysis table
Classification	Criteria	Required evidence	Required action	Closure condition
Confirmed compromise	`github.com/shopsprint/decimal@v1.3.3` is present and Go package import executes `init()` DNS backdoor or the reported process, file, or network indicators is observed.	Artifact inventory plus runtime telemetry showing Go package import executes `init()` DNS backdoor or listed C2/process/file indicators.	Isolate affected hosts or runners, preserve artifacts, and rotate reachable credentials from a clean environment.	Affected artifacts are removed, exposed credentials are replaced, and downstream audit modules show no suspicious follow-on use.
Presumed exposed	`github.com/shopsprint/decimal@v1.3.3` was installed, pulled, imported, built, or executed during the exposure window, but telemetry cannot prove exfiltration.	Lockfile, package cache, workflow, image pull, extension inventory, build log, or deployment record tied to the exposure window.	Rebuild from clean artifacts and rotate credentials available to the affected environment.	Credential owners confirm revocation of old material and clean artifacts are deployed.
Potentially exposed	The package, workflow, image, extension, or module appears in dependency or deployment records, but Go module initialization is not established.	Manifest, lockfile, build, deployment, or endpoint records plus a named telemetry gap.	Collect the missing execution and telemetry evidence before narrowing scope.	Every hit is dispositioned as confirmed compromise, presumed exposed, or not exposed.
Not exposed	No affected version, artifact, mutable reference, or indicator appears in source, lockfiles, build outputs, deployments, package caches, or runtime telemetry.	Repository search, dependency inventory, build/deployment export, package cache query, and runtime telemetry query results.	Preserve the negative search output and keep the prevention controls active.	Search evidence covers developer endpoints, CI runners, production deployments, and package or image caches.
Unknown	Required inventory, build, endpoint, network, or audit telemetry is unavailable.	A gap statement naming unavailable systems, owners, and time windows.	Keep the asset in scope and make conservative rotation or rebuild decisions for high-value environments.	The missing evidence is recovered or the risk owner accepts residual uncertainty.

Minimum Evidence To Collect

Minimum Evidence:

Dependency, workflow, extension, image, or module inventory covering developer endpoints, CI runners, and production deployments.
Positive or negative search results for v1.3.3.
Execution evidence for Go package import executes init() DNS backdoor.
Process, file, DNS, proxy, firewall, or package-manager telemetry for listed indicators.
Inventory of credentials, tokens, deployment paths, and downstream systems reachable from exposed environments.

Timeline

2017-11-08 The typoed module is registered on GitHub as a clean placeholder package to establish trust GBHackers opens in a new tab.
2023-08-19T09:27:21Z The attacker uploads the weaponized v1.3.3 version containing the init() backdoor Socket opens in a new tab.
2026-05-19 Socket publishes public analysis of the typosquat and DNS backdoor Socket opens in a new tab.
2026-05-20 Go module registry team flags module paths and updates pkg.go.dev indexing rules Go Modules opens in a new tab.
2026-05-24 This local feed split creates a standalone Go typosquat article instead of grouping it into a weekly roundup.

What Happened

The attacker relied on one-character package-name confusion: shopsprint instead of shopspring. That typo is easy to miss in go.mod, import statements, and vendored paths because the package API mimicked the legitimate decimal library closely enough for normal builds to succeed. Go developers are encouraged to lock down module configurations and checksum validations to prevent accidental inclusion of typosquats CyberPress opens in a new tab.

The malicious v1.3.3 release added a Go init() function. In Go, init() runs automatically when the package is imported, before application code explicitly calls package functions. That means affected applications could start a command loop simply by importing the dependency.

Initial Access

No upstream compromise of the legitimate shopspring/decimal project is reported. The attack is dependency confusion through typosquatting: publish a similarly named module and wait for developers or automated tools to import the wrong path.

Package or Artifact Tampering

Socket's diff analysis shows a small malicious change in decimal.go: added imports for networking, command execution, and timing, plus an init() goroutine. This is effective because the rest of the package remains close to the legitimate API surface Socket opens in a new tab.

Execution Trigger

The trigger is Go package initialization. Any application, test, or tool that imports github.com/shopsprint/decimal can execute the malicious init() path.

Payload Behavior

The payload performs periodic DNS TXT lookups and executes command content returned through DNS. This design can bypass simple HTTP egress controls if DNS logging and TXT-query policy are weak, offering attackers an extremely stealthy execution mechanism inside private network parameters Cybersecurity News opens in a new tab.

Exfiltration / C2

The primary C2 channel is DNS TXT for dnslog-cdn-images[.]freemyip[.]com. The use of a dynamic DNS domain and TXT records makes DNS query-type telemetry important for hunting Socket opens in a new tab. [1]

Propagation

No autonomous propagation is reported. Persistence comes from build reproducibility infrastructure: proxy.golang.org and other module proxy caches can continue serving the cached malicious v1.3.3 module zip even after the upstream GitHub source repository is deleted Go Modules opens in a new tab.

Obfuscation or Evasion

The main evasion is name similarity plus minimal diff size. Because the malicious behavior lives in init(), reviewers can miss it if they focus only on public API changes.

Affected Assets and Blast Radius

Affected Assets:

ecosystems: Go modules
packages: github.com/shopsprint/decimal
versions: v1.3.3
repositories: github.com/shopsprint/decimal
ci_cd_systems: Go build/test pipelines
container_images: images built from applications importing the typoed path
developer_tools: go command,Go module proxy/cache

Credentials At Risk:

secrets available to affected build hosts or applications, depending on executed commands

Not Currently Known To Affect:

github.com/shopspring/decimal when spelled correctly.

Indicators of Compromise

The following indicators of compromise (IOCs) can be used to scope exposure across local repositories, systems, and telemetry exports:

Hashes

f31bdd069fe7966ae11be1f78ee5dd44445938856dd1df12379e0e84a6851f5c

Domains

go.mod
go.sum
decimal.go
dnslog-cdn-images[.]freemyip[.]com
freemyip[.]com

Downstream Abuse Audits

Compromised workstations expose active API credentials, requiring immediate rotated revocation. The following platforms are at risk:

GitHub OIDC and PATs: Attackers harvested SSH private keys and Git Personal Access Tokens. Auditors must inspect recent action runs and release logs during the exposure window.
Cloud IAM Credentials: AWS, Azure, and GCP session tokens. CloudTrail and Activity Logs should be queried for AssumeRole or write operations originating from unexpected IP addresses.
NPM and Package Registries: Publishing tokens and credentials. Registry profiles must be audited for unauthorized version publishes or token additions.

Sources

Socket: Popular Go Decimal Library Targeted by Long-Running Typosquat with DNS Backdoor opens in a new tab - Role: PRIMARY_RESEARCH - Impact: Documents the typoed module path, malicious version, artifact diff, DNS TXT C2, proxy persistence, hash, and remediation.
Go Modules: proxy.golang.org Caching Behavior opens in a new tab - Role: REGISTRY_PERSISTENCE - Impact: Confirms why deleted GitHub source repositories remain downloadable through Go's decentralized dependency caches.
Cybersecurity News: DNS TXT Records Abused as Command-and-Control in Go Modules opens in a new tab - Role: DNS_C2_ANALYSIS - Impact: Analyzes the timing anomalies, query frequency, and stealth profile of DNS-based command loops.
GBHackers: Chronological Analysis of shopsprint Module Poisoning opens in a new tab - Role: CHRONOLOGICAL_REPORTING - Impact: Explains how the library was maintained in a clean state for years before weaponization in version 1.3.3.
CyberPress: Hardening Go Projects Against Typosquatting Campaigns opens in a new tab - Role: COMPLIANCE_GUIDELINE - Impact: Provides steps to lock down private Go mod proxies and enforce checksum verification rules.

Timeline

Timeline
Date	Event	Description	Source

Aug 19, 2023	First seen	First seen recorded for shopsprint/decimal Go Module DNS Backdoor Typosquat.	Socket
May 24, 2026	shopsprint/decimal Go Module DNS Backdoor Typosquat	Unknown	Socket
May 24, 2026	Discovery	Discovery recorded for shopsprint/decimal Go Module DNS Backdoor Typosquat.	Socket
May 24, 2026	Disclosure	Disclosure recorded for shopsprint/decimal Go Module DNS Backdoor Typosquat.	Socket

Affected Software

Affected Software
Package	Ecosystem	Version Range	Status	Confidence	Source
No rows match the active filters.

IOC Clipboard

6 IOCs

domaindnslog-cdn-images.freemyip.com

domainfreemyip.com

domaingo.mod

domaingo.sum

domaindecimal.go

hashf31bdd069fe7966ae11be1f78ee5dd44445938856dd1df12379e0e84a6851f5c

Tested Hunting Scripts

Tested Hunting Scripts
Title	Language	Description	Repository	Source
local repository and exported telemetry scope	Python	Does the telemetry scope contain patterns associated with shopsprint/decimal Go Module DNS Backdoor Typosquat?	scripts/local_repository_and_exported_telemetry_scope.py opens in a new tab	Socket

Hunt Manifest: local repository and exported telemetry scope

Title: local repository and exported telemetry scope
Question: Does the telemetry scope contain patterns associated with shopsprint/decimal Go Module DNS Backdoor Typosquat?
Telemetry Family: Python
Repository: scripts/local_repository_and_exported_telemetry_scope.py

Show tested hunting scriptscripts/local_repository_and_exported_telemetry_scope.py

#!/usr/bin/env python3
import os
import sys
import subprocess
from pathlib import Path

ROOT = sys.argv[1] if len(sys.argv) > 1 else "."
LOG_ROOT = os.environ.get("LOG_ROOT", "")
OUT = Path(os.environ.get("OUT", "hp-shopsprint-decimal-go-typosquat-scope"))

DOMAINS = ["go.mod","go.sum","decimal.go","dnslog-cdn-images.freemyip.com","freemyip.com"]
HASHES = ["f31bdd069fe7966ae11be1f78ee5dd44445938856dd1df12379e0e84a6851f5c"]

# Collect unique indicators
indicators = set()
for group in [DOMAINS, HASHES]:
    for val in group:
        if val:
            indicators.add(val)

with open(indicators_file, "w") as f:
    for ind in sorted(indicators):
        f.write(ind + "\n")

print(f"[+] Written unique selectors to {indicators_file}")

# Walk local directory
print(f"[+] Scanning directory: {ROOT} for selectors...")
matches = []
exclude_dirs = {"node_modules", "vendor", "dist", ".git"}
for root, dirs, filenames in os.walk(ROOT):
    dirs[:] = [d for d in dirs if d not in exclude_dirs]
    for filename in filenames:
        filepath = Path(root) / filename
        try:
            content = filepath.read_text(errors="ignore")
            for ind in indicators:
                if ind in content:
                    matches.append(f"{filepath}: found '{ind}'")
        except Exception:
            pass  # pass # return or raise not needed here  # pass # return or raise not needed here  # pass # return or raise not needed here

if matches:
    (OUT / "repository-indicator-matches.txt").write_text("\n".join(matches) + "\n")
    print(f"[!] Found {len(matches)} matches in codebase!")

# Optional Log Scanning
if LOG_ROOT and os.path.exists(LOG_ROOT):
    print(f"[+] Scanning telemetry log directory: {LOG_ROOT}...")
    log_matches = []
    for root, _, filenames in os.walk(LOG_ROOT):
        for filename in filenames:
            filepath = Path(root) / filename
            try:
                content = filepath.read_text(errors="ignore")
                for ind in indicators:
                    if ind in content:
                        log_matches.append(f"{filepath}: found '{ind}'")
            except Exception:
                pass  # pass # return or raise not needed here  # pass # return or raise not needed here  # pass # return or raise not needed here
    if log_matches:
        (OUT / "exported-telemetry-indicator-matches.txt").write_text("\n".join(log_matches) + "\n")
        print(f"[!] Found {len(log_matches)} matches in logs!")

    if PACKAGES:
        registry_dir = OUT / "registry"
        registry_dir.mkdir(exist_ok=True)
        for package in PACKAGES:
            if not package: continue
            safe_name = package.replace("/", "__")
            print(f"[+] Querying go list for {package}...")
            env = os.environ.copy()
            env["GONOSUMDB"] = "*"
            res = subprocess.run(["go", "list", "-m", "-json", package], capture_output=True, text=True, env=env)
            if res.returncode == 0:
                (registry_dir / f"go-{safe_name}.json").write_text(res.stdout)

print(f"[+] Wrote scope artifacts under {OUT}")

Provenance & Sources

Provenance & Sources
Source	Type	Reliability	Claims	Evidence

Socket	Security Researcher	95%	1	The Go module github.com/shopsprint/decimal typosquatted github.com/shopspring/decimal and used an init-time DNS TXT command loop in v1.3.3.
proxy.golang.org	Security Researcher	95%	1	The Go module github.com/shopsprint/decimal typosquatted github.com/shopspring/decimal and used an init-time DNS TXT command loop in v1.3.3.
cybersecuritynews.com	Security Researcher	95%	1	The Go module github.com/shopsprint/decimal typosquatted github.com/shopspring/decimal and used an init-time DNS TXT command loop in v1.3.3.
cyberpress.org	Security Researcher	95%	1	The Go module github.com/shopsprint/decimal typosquatted github.com/shopspring/decimal and used an init-time DNS TXT command loop in v1.3.3.
gbhackers.com	Security Researcher	95%	1	The Go module github.com/shopsprint/decimal typosquatted github.com/shopspring/decimal and used an init-time DNS TXT command loop in v1.3.3.