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.
CVE-2026-42501
“—” beside the score: it is equal to NVD's CVSS score.
Score 7.5 from GitHub Security Advisory (severity: HIGH) published 2026-05-07. NVD baseline CVSS 7.5; sources differ by 0.0.
Also known asEUVD-2026-28433 (ENISA EUVD) · GHSA-qf3q-3h68-mmh2 (GitHub Security Advisories)Source: ENISA EUVD
- High severity, but no confirmed exploitation yet
A fix is available — apply it.
- CVSS v3
- 7.5
- EG Score
- 7.5HIGHmedium confidence
- EG Risk
- 34EG Risk 34/100
EG Risk is EchelonGraph's 0–100 priority score. It fuses impact severity (EG Severity, the CVSS base score, never the KEV-floored or EPSS-lifted EG Score) with real-world exploitation and automatability, under weights EchelonGraph set by hand, so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner.
How it’s computed (value × EchelonGraph’s weight)Severity75% × 45%Impact severity (EG Severity): CVSS 7.5 of 10. Never the KEV-floored or EPSS-lifted EG Score.Exploitation0.2% × 40%FIRST EPSS: the 30-day exploitation probability when EchelonGraph scored this CVE.Automatability0% × 15%CISA's SSVC Automatable value: no (Vulnrichment).SSVC (CISA's decision table, applied by EchelonGraph): Track at low or medium mission impact; Track* at high (mission-essential systems).Exploitation none (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact total (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE.Action: A fix is available. Apply it within your standard update timelines. - EPSS PROB
- 0.2%
- EPSS %ILE
- 13th
- KEV
- Not listed
What the EG score is made of (scorer v4.0: the three questions the 0–10 score mixes, published apart · methodology)
The EG score (7.5): severity, escalated by confirmed exploitation. This CVE's 7.5 is its impact severity (EG Severity), not escalated.
- EG Severity
- 7.5 HIGHCVSS-B, impact only: no KEV listing, EPSS or EG-KEV tier raises it.GitHub Security Advisory CVSS
- EG Likelihood
- 0.2% within 30 daysSource: FIRST EPSS (model v2026.06.15, score date 2026-10-29). FIRST's exploitation probability, not an EchelonGraph model.
- Confirmed exploitation
- None on record (CISA KEV, EG-KEV Tier 1)Reported apart from the likelihood: an observed fact, not a probability.
- EG Priority
- SSVC Track at medium mission impactTrack at low or medium mission impact; Track* at high (mission-essential systems).CISA BOD 26-04: 14 days if the affected system is publicly exposed; Fix on system upgrade if it is not.Each input and its source, and whom BOD 26-04 binds: the SSVC and BOD 26-04 blocks below.
SSVC (CISA's decision table, applied by EchelonGraph)Track at low or medium mission impact; Track* at high (mission-essential systems).
A fix is available. Apply it within your standard update timelines.
Exploitation none (CISA Vulnrichment) · Automatable no (CISA Vulnrichment) · Technical impact total (CISA Vulnrichment). All three are CISA's SSVC values (Vulnrichment). EchelonGraph applied CISA's decision table to them; CISA publishes SSVC inputs and the table, not a decision for each CVE. Mission impact is CISA's Mission & Well-being decision point, and only you can judge it. CISA's table makes it high when Mission Prevalence is Essential — the vulnerable component "directly provides capabilities that constitute at least one MEF for at least one entity" (MEF: mission essential function) — or when Public Well-Being Impact is Irreversible: "multiple fatalities are likely", the cyber-physical system "is likely lost or destroyed", "extreme or serious externalities" are imposed on other parties, or social systems such as elections or the financial grid "are destabilized and potentially collapse". CISA's decision table
BOD 26-04 (CISA's remediation timeline, Table 1)14 days if the affected system is publicly exposed; Fix on system upgrade if it is not.
The score's inputs: In CISA KEV no (CISA's KEV catalog) · Automatable no (CISA Vulnrichment) · Technical impact total (CISA Vulnrichment). Whether your system is publicly exposed is yours to answer. BOD 26-04 binds US Federal Civilian Executive Branch agencies; for anyone else it is CISA's published timeline, a reference rather than an obligation. The directive · how EchelonGraph applies it
Published
May 7, 2026
Last Modified
May 13, 2026
Advisory Details (4)
Auto-updated Jun 6, 2026cmd/go: malicious module proxy can bypass checksum database (fix CVE-2026-42501) · Issue #79070 · golang/go · GitHub
https://go.dev/issue/79070Vendor Advisories for CVE-2026-42501(11)
These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.
- RHSA-2026:61253Red Hat Product SecurityHigh
Red Hat Security Advisory: golang security update
- RHSA-2026:57649Red Hat Product SecurityHigh
Red Hat Security Advisory: golang security update
- RHSA-2026:49712Red Hat Product SecurityHigh
Red Hat Security Advisory: golang security update
- RHSA-2026:49702Red Hat Product SecurityHigh
Red Hat Security Advisory: golang security update
- RHSA-2026:32987Red Hat Product SecurityMedium
Red Hat Security Advisory: Red Hat Hardened Images RPMs Security Update
- RHSA-2026:23264Red Hat Product SecurityHigh
Red Hat Security Advisory: Red Hat Hardened Images RPMs bug fix and enhancement update
- RHSA-2026:23262Red Hat Product SecurityHigh
Red Hat Security Advisory: Red Hat Hardened Images RPMs bug fix and enhancement update
- RHSA-2026:22112Red Hat Product SecurityHigh
Red Hat Security Advisory: go-toolset:rhel8 security update
- +3 more
Patch Availability(10)
| Vendor / Ecosystem | Fix (by version range) / Patch | Released | Source |
|---|---|---|---|
| redhat | golang-0:1.26.5-1.el9_2 | 2026-08-31 | redhat |
| redhat | golang-0:1.26.5-1.el9_4 | 2026-08-20 | redhat |
| redhat | golang-0:1.26.5-1.el9_6 | 2026-08-03 | redhat |
| redhat | golang-0:1.26.5-1.el10_0 | 2026-08-03 | redhat |
| redhat | golang-fips1-25-main-1.25.9-0.1.1.hum1 | 2026-06-29 | redhat |
| redhat | golang1-25-main-1.25.11-2.hum1 | 2026-06-04 | redhat |
| redhat | golang1-26-main-1.26.4-2.hum1 | 2026-06-04 | redhat |
| redhat | golang-0:1.26.3-1.el9_8 | 2026-06-01 | redhat |
| redhat | golang-0:1.26.3-4.el10_2 | 2026-06-01 | redhat |
| redhat | go-toolset:rhel8-8100020260518131104.a3795dee | 2026-06-01 | redhat |
Patches are aggregated from vendor advisories (Red Hat, Microsoft, Cisco, GitHub) and package ecosystems (OSV, GHSA). Multiple rows for the same upstream release have been deduplicated.
Affected Packages
(6 across 5 ecosystems)
Debian:14(2)
| Package | Vulnerable range | Fix by version range | Dependents |
|---|---|---|---|
| golang-1.25 | 1.25.0-1 ... 1.25.9-1 (11 versions) |
| — |
| golang-1.26 | 1.26.0-1 ... 1.26~rc3-2 (9 versions) |
| — |
Debian:11(1)
| Package | Vulnerable range | Fix by version range | Dependents |
|---|---|---|---|
| golang-1.15 | 1.15.15-1 ... 1.15.9-6 (10 versions) |
| — |
Debian:12(1)
| Package | Vulnerable range | Fix by version range | Dependents |
|---|---|---|---|
| golang-1.19 | 1.19.10-1 ... 1.19.9-1 (12 versions) |
| — |
Debian:13(1)
| Package | Vulnerable range | Fix by version range | Dependents |
|---|---|---|---|
| golang-1.24 | 1.24.12-1 ... 1.24.9-1 (10 versions) |
| — |
Go(1)
| Package | Vulnerable range | Fix by version range | Dependents |
|---|---|---|---|
| toolchain | — |
| — |
Weakness Classification(1)
MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.
Data Freshness Timeline
(refreshed 10× in last 7d / 44× in last 30d)
Each row is a time one of our pipelines fetched, updated or re-scored this CVE. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. An arrow marks a change the record states ("CVSS v3 → 9.1"); EPSS and GHSA rows show the values recorded at that time, not what changed (EPSS values are rounded; hover one for the exact figures). Most recent first.
Showing the most recent 100 of 256 refreshes on record for this CVE.
A repeat, a row identical to one the same pipeline wrote less than 10 seconds earlier, is not a separate refresh and is not counted. None are among the latest 100 rows. The 156 oldest rows on record are not shown and were not checked, so the counts can still include repeats.
- 2026-11-01 16:34 UTCEPSS rescoreEPSS 0.2% · 13th percentile
- 2026-10-31 16:32 UTCEPSS rescoreEPSS 0.2% · 13th percentile
- 2026-10-30 16:34 UTCEPSS rescoreEPSS 0.2% · 13th percentile
- 2026-10-30 05:02 UTCEG score recompute
- 2026-10-30 05:02 UTCVendor advisory
- 2026-10-30 05:02 UTCGHSA enrichmentGHSA-qf3q-3h68-mmh2 · GitHub severity HIGH · GitHub CVSS 7.5
- 2026-10-29 16:33 UTCEPSS rescoreEPSS 0.2% · 13th percentile
- 2026-10-28 16:32 UTCEPSS rescoreEPSS 0.2% · 13th percentile
- 2026-10-27 16:32 UTCEPSS rescoreEPSS 0.2% · 13th percentile
- 2026-10-26 16:31 UTCEPSS rescoreEPSS 0.2% · 13th percentile
- 2026-10-25 16:33 UTCEPSS rescoreEPSS 0.2% · 13th percentile
- 2026-10-25 14:29 UTCEG score recompute
- 2026-10-24 16:33 UTCEPSS rescoreEPSS 0.3% · 19th percentile
- 2026-10-23 21:44 UTCEG score recompute
- 2026-10-23 21:44 UTCGHSA enrichmentGHSA-qf3q-3h68-mmh2 · GitHub severity HIGH · GitHub CVSS 7.5
- 2026-10-23 16:31 UTCEPSS rescoreEPSS 0.3% · 19th percentile
- 2026-10-22 16:34 UTCEPSS rescoreEPSS 0.3% · 19th percentile
- 2026-10-21 16:33 UTCEPSS rescoreEPSS 0.3% · 19th percentile
- 2026-10-20 16:33 UTCEPSS rescoreEPSS 0.3% · 19th percentile
- 2026-10-19 16:32 UTCEPSS rescoreEPSS 0.3% · 19th percentile
- 2026-10-18 16:32 UTCEPSS rescoreEPSS 0.3% · 19th percentile
- 2026-10-18 03:41 UTCEG score recompute
- 2026-10-17 16:34 UTCEPSS rescoreEPSS 0.3% · 19th percentile
- 2026-10-17 14:25 UTCEG score recompute
- 2026-10-17 14:25 UTCVendor advisory
Show 75 moreShow fewer
- 2026-10-17 14:24 UTCGHSA enrichmentGHSA-qf3q-3h68-mmh2 · GitHub severity HIGH · GitHub CVSS 7.5
- 2026-10-16 16:42 UTCEPSS rescoreEPSS 0.3% · 19th percentile
- 2026-10-15 16:32 UTCEPSS rescoreEPSS 0.3% · 19th percentile
- 2026-10-14 16:33 UTCEPSS rescoreEPSS 0.3% · 19th percentile
- 2026-10-13 16:34 UTCEPSS rescoreEPSS 0.3% · 19th percentile
- 2026-10-12 16:34 UTCEPSS rescoreEPSS 0.3% · 19th percentile
- 2026-10-12 16:07 UTCEG score recompute
- 2026-10-11 19:49 UTCEG score recompute
- 2026-10-11 17:03 UTCEG score recompute
- 2026-10-11 14:29 UTCEG score recompute
- 2026-10-11 13:48 UTCEPSS rescoreEPSS 0.3% · 19th percentile
- 2026-10-10 20:00 UTCEPSS rescoreEPSS 0.3% · 19th percentile
- 2026-10-09 20:07 UTCEPSS rescoreEPSS 0.3% · 19th percentile
- 2026-10-08 17:12 UTCEPSS rescoreEPSS 0.3% · 19th percentile
- 2026-10-07 23:48 UTCEPSS rescoreEPSS 0.3% · 19th percentile
- 2026-10-06 15:17 UTCEPSS rescoreEPSS 0.3% · 19th percentile
- 2026-10-05 17:43 UTCEPSS rescoreEPSS 0.3% · 19th percentile
- 2026-10-04 23:22 UTCEPSS rescoreEPSS 0.3% · 19th percentile
- 2026-10-03 14:25 UTCEPSS rescoreEPSS 0.3% · 19th percentile
- 2026-10-01 19:50 UTCEPSS rescoreEPSS 0.3% · 18th percentile
- 2026-09-30 15:03 UTCEPSS rescoreEPSS 0.3% · 18th percentile
- 2026-09-30 08:41 UTCOSV refresh
- 2026-09-27 13:48 UTCEPSS rescoreEPSS 0.3% · 18th percentile
- 2026-09-26 15:58 UTCEPSS rescoreEPSS 0.3% · 18th percentile
- 2026-09-23 17:53 UTCEPSS rescoreEPSS 0.2% · 14th percentile
- 2026-09-20 20:15 UTCEPSS rescoreEPSS 0.2% · 14th percentile
- 2026-09-18 19:28 UTCEPSS rescoreEPSS 0.2% · 14th percentile
- 2026-09-17 19:31 UTCEPSS rescoreEPSS 0.2% · 14th percentile
- 2026-09-16 14:08 UTCEPSS rescoreEPSS 0.2% · 14th percentile
- 2026-09-16 05:15 UTCEPSS rescoreEPSS 0.2% · 13th percentile
- 2026-09-13 16:47 UTCEPSS rescoreEPSS 0.2% · 13th percentile
- 2026-09-12 15:01 UTCEPSS rescoreEPSS 0.2% · 13th percentile
- 2026-09-11 15:23 UTCOSV refresh
- 2026-09-11 14:53 UTCEPSS rescoreEPSS 0.2% · 13th percentile
- 2026-09-11 09:37 UTCEPSS rescoreEPSS 0.2% · 13th percentile
- 2026-09-10 09:34 UTCEPSS rescoreEPSS 0.2% · 13th percentile
- 2026-09-08 22:00 UTCEPSS rescoreEPSS 0.2% · 13th percentile
- 2026-09-07 16:01 UTCEPSS rescoreEPSS 0.2% · 13th percentile
- 2026-09-06 13:47 UTCEPSS rescoreEPSS 0.2% · 13th percentile
- 2026-09-04 05:06 UTCEPSS rescoreEPSS 0.2% · 13th percentile
- 2026-09-02 14:12 UTCEPSS rescoreEPSS 0.2% · 13th percentile
- 2026-09-01 13:54 UTCEPSS rescoreEPSS 0.2% · 13th percentile
- 2026-08-30 19:17 UTCEPSS rescoreEPSS 0.2% · 13th percentile
- 2026-08-30 01:22 UTCEPSS rescoreEPSS 0.2% · 13th percentile
- 2026-08-28 21:41 UTCEPSS rescoreEPSS 0.2% · 13th percentile
- 2026-08-27 14:25 UTCEPSS rescoreEPSS 0.2% · 13th percentile
- 2026-08-26 14:46 UTCEPSS rescoreEPSS 0.2% · 13th percentile
- 2026-08-25 13:49 UTCEPSS rescoreEPSS 0.2% · 13th percentile
- 2026-08-23 19:33 UTCEG score recompute
- 2026-08-23 19:33 UTCGHSA enrichmentGHSA-qf3q-3h68-mmh2 · GitHub severity HIGH · GitHub CVSS 7.5
- 2026-08-23 00:19 UTCEPSS rescoreEPSS 0.2% · 14th percentile
- 2026-08-21 23:49 UTCEPSS rescoreEPSS 0.2% · 14th percentile
- 2026-08-20 22:55 UTCEPSS rescoreEPSS 0.2% · 14th percentile
- 2026-08-19 17:03 UTCEPSS rescoreEPSS 0.2% · 14th percentile
- 2026-08-18 13:48 UTCEPSS rescoreEPSS 0.2% · 14th percentile
- 2026-08-17 13:47 UTCEPSS rescoreEPSS 0.2% · 14th percentile
- 2026-08-17 12:43 UTCEG score recompute
- 2026-08-17 12:43 UTCGHSA enrichmentGHSA-qf3q-3h68-mmh2 · GitHub severity HIGH · GitHub CVSS 7.5
- 2026-08-16 14:56 UTCEPSS rescoreEPSS 0.2% · 14th percentile
- 2026-08-16 04:42 UTCEG score recompute
- 2026-08-16 04:42 UTCGHSA enrichmentGHSA-qf3q-3h68-mmh2 · GitHub severity HIGH · GitHub CVSS 7.5
- 2026-08-16 02:14 UTCEPSS rescoreEPSS 0.2% · 14th percentile
- 2026-08-15 01:30 UTCEPSS rescoreEPSS 0.2% · 13th percentile
- 2026-08-14 15:05 UTCGHSA enrichmentGHSA-qf3q-3h68-mmh2 · GitHub severity HIGH · GitHub CVSS 7.5
- 2026-08-14 03:17 UTCEG score recompute
- 2026-08-14 03:17 UTCGHSA enrichmentGHSA-qf3q-3h68-mmh2 · GitHub severity HIGH · GitHub CVSS 7.5
- 2026-08-13 22:00 UTCEPSS rescoreEPSS 0.2% · 13th percentile
- 2026-08-13 04:39 UTCGHSA enrichmentGHSA-qf3q-3h68-mmh2 · GitHub severity HIGH · GitHub CVSS 7.5
- 2026-08-12 16:52 UTCEG score recompute
- 2026-08-12 16:52 UTCGHSA enrichmentGHSA-qf3q-3h68-mmh2 · GitHub severity HIGH · GitHub CVSS 7.5
- 2026-08-12 13:51 UTCEPSS rescoreEPSS 0.2% · 13th percentile
- 2026-08-11 15:55 UTCEG score recompute
- 2026-08-11 15:54 UTCGHSA enrichmentGHSA-qf3q-3h68-mmh2 · GitHub severity HIGH · GitHub CVSS 7.5
- 2026-08-11 13:43 UTCEPSS rescoreEPSS 0.2% · 13th percentile
- 2026-08-11 01:46 UTCEG score recompute
Related CVEs(same product + same vendor + same CWE)
Same product
10 shownGo:toolchain
Same vendor
10 shownredhat:RHSA-2026:22112 · redhat:RHSA-2026:23262
Frequently asked(5)
What is CVE-2026-42501?
When was the CVE record for CVE-2026-42501 published?
Is CVE-2026-42501 actively exploited?
What is the CVSS score of CVE-2026-42501?
How do I remediate CVE-2026-42501?
Dependency Blast Radius
See which npm, PyPI, Go, and Maven packages are affected by CVE-2026-42501
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