CVE-2026-42501
📛 CVE Title
Malicious module proxy can bypass checksum database in cmd/go
Description
A malicious module proxy can exploit a flaw in the go command's validation of module checksums to bypass checksum database validation. This vulnerability affects any user using an untrusted module proxy (GOMODPROXY) or checksum database (GOSUMDB). A malicious module proxy can serve altered versions of the Go toolchain. When selecting a different version of the Go toolchain than the currently installed toolchain (due to the GOTOOLCHAIN environment variable, or a go.work or go.mod with a toolchain line), the go command will download and execute a toolchain provided by the module proxy. A malicious module proxy can bypass checksum database validation for this downloaded toolchain. Since this vulnerability affects the security of toolchain downloads, setting GOTOOLCHAIN to a fixed version is not sufficient. You must upgrade your base Go toolchain. The go tool always validates the hash of a toolchain before executing it, so fixed versions will refuse to execute any cached, altered versions of the toolchain. The go tool trusts go.sum files to contain accurate hashes of the current module's dependencies. A malicious proxy exploiting this vulnerability to serve an altered module will have caused an incorrect hash to be recorded in the go.sum. Users who have configured a non-trusted GOPROXY can determine if they have been affected by running "rm go.sum ; go mod tidy ; go mod verify", which will revalidate all dependencies of the current module. The specific flaw in more detail: The go command consults the checksum database to validate downloaded modules, when a module is not listed in the go.sum file. It verifies that the module hash reported by the checksum database matches the hash of the downloaded module. If, however, the checksum database returns a successful response that contains no entry for the module, the go command incorrectly permitted validation to succeed. A module proxy may mirror or proxy the checksum database, in which case the go command will not connect to the checksum database directly. Checksums reported by the checksum database are cryptographically signed, so a malicious proxy cannot alter the reported checksum for a module. However, a proxy which returns an empty checksum response, or a checksum response for an unrelated module, could cause the go command to proceed as if a downloaded module has been validated.
Overview
- State
- PUBLISHED
- Assigner (CNA)
- Go
- CVSS severity
- high
- CVSS score
- 7.5 / 10
- CVSS vector
AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H- Effective score
- 7.5 / 10 HIGH source: CNA overview
- MSRC score
- 7.5 / 10 HIGH MS rating: Important
- CWE(s)
-
CWE-347: Improper Verification of Cryptographic Signature - Reserved
- 2026-04-28
- Published
- 2026-05-07 21:41 UTC
- Last updated
- 2026-05-08 17:48 UTC
- Source
- https://raw.githubusercontent.com/CVEProject/cvelistV5/main/cves/2026/42xxx/CVE-2026-42501.json
- Linked Threat
- CVE-2026-42501 — CVE-2026-42501
NVD triage scoring NVD CVE 2.0
Layer NVD adds on top of the CNA's CVE record — published / last-modified timestamps, exploitability / impact subscores, and the FIRST.org EPSS probability that this CVE will be exploited in the wild in the next 30 days.
- NVD published
- 2026-05-07 20:16:44 UTC
- NVD last modified
- 2026-05-13 16:59:42 UTC
- NVD CVSS v3.1
- 7.5 / 10 HIGH source: 134c704f-9b21-4f2e-91b3-4a467353bcc0
- NVD CVSS vector
CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H- Exploitability subscore
- 1.6 / 10
- Impact subscore
- 5.9 / 10
- EPSS score
- 0.0001 (probability of exploitation in next 30 days)
- EPSS percentile
- 0.77% vs all CVEs — higher = more likely to be exploited, as of 2026-05-24
NVD-assigned CWE(s):
CWE-347
(differs from the CNA list above)
NVD / KEV / EPSS data refreshed 2026-05-25 09:24 UTC. Re-run the 🛰 Backfill from NVD button above to refresh.
European Union Vulnerability Database ENISA EUVD
ENISA's official EU repository for curated vulnerability intelligence. Carries a separate identifier (EUVD-YYYY-NNNN) and frequently exposes an earlier-published description + CVSS than NVD does.
- EUVD ID
-
EUVD-2026-28433 - Assigner
- Go
- Published
- May 7, 2026, 7:41:19 PM
- Updated
- May 8, 2026, 3:48:47 PM
- EUVD base score (CVSS 3.1)
-
7.5 / 10
CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H - EUVD-reported EPSS
- 0.0100
- Vendors
- Go toolchain
- Products
-
cmd/go (1.26.0-0 <1.26.3)cmd/go (0 <1.25.10)
ENISA description: A malicious module proxy can exploit a flaw in the go command's validation of module checksums to bypass checksum database validation. This vulnerability affects any user using an untrusted module proxy (GOMODPROXY) or checksum database (GOSUMDB). A malicious module proxy can serve altered versions of the Go toolchain. When selecting a different version of the Go toolchain than the currently installed toolchain (due to the GOTOOLCHAIN environment variable, or a go.work or go.mod with a toolchain line), the go command will download and execute a toolchain provided by the module proxy. A malicious module proxy can bypass checksum database validation for this downloaded toolchain. Since this vulnerability affects the security of toolchain downloads, setting GOTOOLCHAIN to a fixed version is not sufficient. You must upgrade your base Go toolchain. The go tool always validates the hash of a toolchain before executing it, so fixed versions will refuse to execute any cached, altered versions of the toolchain. The go tool trusts go.sum files to contain accurate hashes of the current module's dependencies. A malicious proxy exploiting this vulnerability to serve an altered module will have caused an incorrect hash to be recorded in the go.sum. Users who have configured a non-trusted GOPROXY can determine if they have been affected by running "rm go.sum ; go mod tidy ; go mod verify", which will revalidate all dependencies of the current module. The specific flaw in more detail: The go command consults the checksum database to validate downloaded modules, when a module is not listed in the go.sum file. It verifies that the module hash reported by the checksum database matches the hash of the downloaded module. If, however, the checksum database returns a successful response that contains no entry for the module, the go command incorrectly permitted validation to succeed. A module proxy may mirror or proxy the checksum database, in which case the go command will not connect to the checksum database directly. Checksums reported by the checksum database are cryptographically signed, so a malicious proxy cannot alter the reported checksum for a module. However, a proxy which returns an empty checksum response, or a checksum response for an unrelated module, could cause the go command to proceed as if a downloaded module has been validated.
Microsoft Security Response Center MSRC
Microsoft's vendor-authoritative record from the Security Update Guide — its own CVSS score, impact, severity rating, exploit assessment, and KB-article fixes. Refreshed 2026-08-12 01:09 UTC (source: CVRF).
- MS severity
- Important
- MS CVSS base score
- 7.5 / 10 (temporal 7.5)
CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H - Release
- 2026-May
Affected products (1)
| Vendor | Product | Versions | Platforms |
|---|---|---|---|
| Go toolchain | cmd/go |
0 (affected),
1.26.0-0 (affected)
|
— |
Affected products — CPE 2.3 (1) NVD
NVD's normalized CPE 2.3 matchers, used by vendor tools (vulnerability scanners, asset managers) for automated detection. Compare with the CNA's free-text "Affected products" section above.
cpe:2.3:a:golang:go:*:*:*:*:*:*:*:*
Vendor references (4)
References embedded in the original CVE record by the assigning CNA.
MITRE references (4) cveawg.mitre.org
Pulled from MITRE's CVE Services API by the 🛰 Backfill from MITRE button.
Web references (9)
DuckDuckGo results ranked by threat-intel / vendor advisory domains. Generated by the 🔎 Find references (web) button above — same flow as the Remediations search.
- MSRC update guide: CVE-2026-42501 msrc
- http://go.work rapid7:go.work
- https://attackerkb.com/topics/CVE-2026-42501 rapid7:attackerkb.com
- https://euvd.enisa.europa.eu/vulnerability/EUVD-2026-28433 rapid7:euvd.enisa.europa.eu
- http://cwe.mitre.org/data/definitions/347.html rapid7:cwe.mitre.org
- https://security.alpinelinux.org/vuln/CVE-2026-42501 rapid7:security.alpinelinux.org
- https://www.first.org/epss/ tenable:www.first.org
- https://nvd.nist.gov/vuln/detail/CVE-2026-42501 tenable:nvd.nist.gov
- https://www.cve.org/CVERecord?id=CVE-2026-42501 tenable:www.cve.org
NVD-tagged references (4)
Reference list NVD curates from the CNA record, vendor advisories, and third-party reports. The tag chips below are NVD's analyst-assigned categories.
- https://go.dev/cl/775321 security@golang.org Patch
- https://go.dev/issue/79070 security@golang.org Issue Tracking
- https://groups.google.com/g/golang-announce/c/qcCIEXso47M security@golang.org Release Notes
- https://pkg.go.dev/vuln/GO-2026-4984 security@golang.org Vendor Advisory
Remediations (20)
Remediations are stored against the linked Threat row; the list below is deduplicated across both pages.
-
web:cybersecuritynews.com
Microsoft released its final Patch Tuesday updates of 2025 on December 9, addressing 56 security vulnerabilities across Windows, Office, Exchange Server, and other components.
2026-05-23 21:08 UTC -
web:en-forum.guildwars2.com
04/14/2026—April 14 Release Notes Note to users of third-party programs: The game may not launch or work properly after we release a new build if you use a third-party program, due to possible incompatibilities. ArenaNet cannot offer support if a third-party modification breaks, interferes with, ...
2026-05-23 21:08 UTC -
web:portal.msrc.microsoft.com
The Security Update Guide provides information on the latest Microsoft security updates, helping users understand and address potential vulnerabilities effectively.
2026-05-23 21:08 UTC -
web:www.computerworld.com
Each month, the team at Readiness analyzes the latest Patch Tuesday updates from Microsoft and provides detailed, actionable testing guidance. The company's Patch Tuesday release for February ...
2026-05-23 21:08 UTC -
web:www.crowdstrike.com
Microsoft's February 2026 Patch Tuesday addresses 59 CVEs , featuring six exploited vulnerabilities, three of which were publicly known, and five Critical vulnerabilities.
2026-05-23 21:08 UTC -
web:www.esri.com
Key highlights The ArcGIS Server Security 2025 update 2 is available This patch resolves 10 Medium severity vulnerabilities This security patch is cumulative, and includes fixes provided in the ArcGIS Server Security 2025 update 1.
2026-05-23 21:08 UTC -
web:www.nickiswift.com
Carrie Underwood's carefully crafted image has hit a rough patch . Political controversy, fan backlash, and TV drama reshaped how the country star is viewed.
2026-05-23 21:08 UTC -
web:www.oracle.com
This Critical Patch Update contains 481 new security patches across the product families listed below. Please note that an MOS note summarizing the content of this Critical Patch Update and other Oracle Software Security Assurance activities is located at April 2026 Critical Patch Update: Executive Summary and Analysis.
2026-05-23 21:08 UTC -
web:www.youtube.com
In today's Daily Fix:Bungie has announced the end of the nine-year-long run of Destiny 2. The final content update will come in June, although support for De...
2026-05-23 21:08 UTC -
web:zecurit.com
Get the complete breakdown of Microsoft's May 2026 Patch Tuesday. We analyze the latest security updates and all critical CVEs .
2026-05-23 21:08 UTC -
web:community.ui.com
Published: May 21, 2026 Updated: May 22, 2026 Version: 1.1 Revision: 1.1 Summary 1 of 5 A malicious actor with access to the network and high privileges could exploit an Improper Input Validation vulnerability found in UniFi OS devices to execute a Command Injection. Affected Products: UniFi OS Server (Version 5.0.6 and earlier) Mitigation : Update your UniFi OS Server to Version 5.0.8 or later ...
2026-05-26 02:46 UTC -
web:docs.openclaw.ai
Migration checklist Use this checklist when you already know your old BlueBubbles config and want the shortest safe path: Verify imsg directly on the Mac that runs Messages.app (imsg chats, imsg history, imsg send, and imsg rpc --help). Copy behavior keys from channels.bluebubbles to channels.imessage: dmPolicy, allowFrom, groupPolicy, groupAllowFrom, groups, includeAttachments ...
2026-05-26 02:46 UTC -
web:en-forum.guildwars2.com
03/31/2026—March 31 Release Notes Note to users of third-party programs: The game may not launch or work properly after we release a new build if you use a third-party program, due to possible incompatibilities. ArenaNet cannot offer support if a third-party modification breaks, interferes with, ...
2026-05-26 02:46 UTC -
web:hi.service-now.com
The Now Support portal is your launchpad to access self-help, get technical support, and manage your ServiceNow instances. Log in to manage upgrades, follow changes, view knowledge content, and more. Formerly HI portal.
2026-05-26 02:46 UTC -
web:msrc.microsoft.com
Security Update Guide - Microsoft Security Response Center
2026-05-26 02:46 UTC -
web:onlyfans.com
OnlyFans is the social platform revolutionizing creator and fan connections. The site is inclusive of artists and content creators from all genres and allows them to monetize their content while developing authentic relationships with their fanbase.
2026-05-26 02:46 UTC -
web:translate.google.com
Google's service, offered free of charge, instantly translates words, phrases, and web pages between English and over 100 other languages.
2026-05-26 02:46 UTC -
web:www.nexusmods.com
U+ for Star Wars Jedi: Survivor is a graphics enhancement and performance improvement mod that provides advanced control over lighting, reflections, and visual effects.
2026-05-26 02:46 UTC -
web:www.virustotal.com
VirusTotal is a platform for scanning files and URLs for viruses, malware, and other threats using multiple antivirus engines.
2026-05-26 02:46 UTC -
web:www.youtube.com
Catch A Monster Roblox Patch 0.32 is live, and this update adds a lot: Draco Spike Evo, the new Mutation Extractor, Jokaire from the Mobius Circus slot machi...
2026-05-26 02:46 UTC
AI Forensic Analysis
Only Available for Registered Users. Sign in to view.
Raw JSON
The full cvelistV5 record. Download as CVE-2026-42501.json.
{
"containers": {
"adp": [
{
"metrics": [
{
"cvssV3_1": {
"attackComplexity": "HIGH",
"attackVector": "NETWORK",
"availabilityImpact": "HIGH",
"baseScore": 7.5,
"baseSeverity": "HIGH",
"confidentialityImpact": "HIGH",
"integrityImpact": "HIGH",
"privilegesRequired": "NONE",
"scope": "UNCHANGED",
"userInteraction": "REQUIRED",
"vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:H",
"version": "3.1"
}
},
{
"other": {
"content": {
"id": "CVE-2026-42501",
"options": [
{
"Exploitation": "none"
},
{
"Automatable": "no"
},
{
"Technical Impact": "total"
}
],
"role": "CISA Coordinator",
"timestamp": "2026-05-08T15:48:05.053316Z",
"version": "2.0.3"
},
"type": "ssvc"
}
}
],
"problemTypes": [
{
"descriptions": [
{
"cweId": "CWE-347",
"description": "CWE-347 Improper Verification of Cryptographic Signature",
"lang": "en",
"type": "CWE"
}
]
}
],
"providerMetadata": {
"dateUpdated": "2026-05-08T15:48:47.404Z",
"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
"shortName": "CISA-ADP"
},
"title": "CISA ADP Vulnrichment"
}
],
"cna": {
"affected": [
{
"collectionURL": "https://pkg.go.dev",
"defaultStatus": "unaffected",
"packageName": "cmd/go",
"product": "cmd/go",
"vendor": "Go toolchain",
"versions": [
{
"lessThan": "1.25.10",
"status": "affected",
"version": "0",
"versionType": "semver"
},
{
"lessThan": "1.26.3",
"status": "affected",
"version": "1.26.0-0",
"versionType": "semver"
}
]
}
],
"credits": [
{
"lang": "en",
"value": "Mundur (https://github.com/M0nd0R)"
}
],
"descriptions": [
{
"lang": "en",
"value": "A malicious module proxy can exploit a flaw in the go command's validation of module checksums to bypass checksum database validation. This vulnerability affects any user using an untrusted module proxy (GOMODPROXY) or checksum database (GOSUMDB). A malicious module proxy can serve altered versions of the Go toolchain. When selecting a different version of the Go toolchain than the currently installed toolchain (due to the GOTOOLCHAIN environment variable, or a go.work or go.mod with a toolchain line), the go command will download and execute a toolchain provided by the module proxy. A malicious module proxy can bypass checksum database validation for this downloaded toolchain. Since this vulnerability affects the security of toolchain downloads, setting GOTOOLCHAIN to a fixed version is not sufficient. You must upgrade your base Go toolchain. The go tool always validates the hash of a toolchain before executing it, so fixed versions will refuse to execute any cached, altered versions of the toolchain. The go tool trusts go.sum files to contain accurate hashes of the current module's dependencies. A malicious proxy exploiting this vulnerability to serve an altered module will have caused an incorrect hash to be recorded in the go.sum. Users who have configured a non-trusted GOPROXY can determine if they have been affected by running \"rm go.sum ; go mod tidy ; go mod verify\", which will revalidate all dependencies of the current module. The specific flaw in more detail: The go command consults the checksum database to validate downloaded modules, when a module is not listed in the go.sum file. It verifies that the module hash reported by the checksum database matches the hash of the downloaded module. If, however, the checksum database returns a successful response that contains no entry for the module, the go command incorrectly permitted validation to succeed. A module proxy may mirror or proxy the checksum database, in which case the go command will not connect to the checksum database directly. Checksums reported by the checksum database are cryptographically signed, so a malicious proxy cannot alter the reported checksum for a module. However, a proxy which returns an empty checksum response, or a checksum response for an unrelated module, could cause the go command to proceed as if a downloaded module has been validated."
}
],
"problemTypes": [
{
"descriptions": [
{
"description": "CWE-347: Improper Verification of Cryptographic Signature",
"lang": "en"
}
]
}
],
"providerMetadata": {
"dateUpdated": "2026-05-07T19:41:19.691Z",
"orgId": "1bb62c36-49e3-4200-9d77-64a1400537cc",
"shortName": "Go"
},
"references": [
{
"url": "https://go.dev/cl/775321"
},
{
"url": "https://go.dev/issue/79070"
},
{
"url": "https://groups.google.com/g/golang-announce/c/qcCIEXso47M"
},
{
"url": "https://pkg.go.dev/vuln/GO-2026-4984"
}
],
"title": "Malicious module proxy can bypass checksum database in cmd/go"
}
},
"cveMetadata": {
"assignerOrgId": "1bb62c36-49e3-4200-9d77-64a1400537cc",
"assignerShortName": "Go",
"cveId": "CVE-2026-42501",
"datePublished": "2026-05-07T19:41:19.691Z",
"dateReserved": "2026-04-28T00:21:12.791Z",
"dateUpdated": "2026-05-08T15:48:47.404Z",
"state": "PUBLISHED"
},
"dataType": "CVE_RECORD",
"dataVersion": "5.2"
}