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CVE-2026-56864— Ignore unrelated, unauthenticated hashes in Lookup in golang.org/x/mod/sumdb

Quick assessment

Affected
Go toolchain cmd/go
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Google Go是美国Google公司开源的一款支持并发编程的脚本语言。 Google Go 1.25.13之前版本、1.26.0至1.26.6之前版本和1.27.0至1.27.0-rc.3之前版本，以及golang.org/x/mod/sumdb 0.40.0之前版本存在加密问题漏洞，该漏洞源于恶意GOSUMDB能够提供不在透明日志中的任意模块内容，可能导致攻击者通过协调的GOPROXY和GOSUMDB向客户端提供无法通过透明日志检测的恶意模块内容。

AI Predicted 5.9 Difficulty: Moderate EPSS 0.30% · P20

Affected Version Matrix 4

VendorProduct Version RangeStatus
Go toolchain cmd/go < 1.25.13 affected
1.26.0-0< 1.26.6 affected
1.27.0-0< 1.27.0-rc.3 affected
golang.org/x/mod golang.org/x/mod/sumdb < 0.40.0 affected
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I. Basic Information for CVE-2026-56864

Vulnerability Information
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Vulnerability Title
Ignore unrelated, unauthenticated hashes in Lookup in golang.org/x/mod/sumdb
Source: CVE Program / CVE List V5
Vulnerability Description
A malicious GOSUMDB was capable of serving arbitrary module content not contained within the transparency log. This attack allows for a coordinating GOPROXY and GOSUMDB to serve a client malicious module content that cannot be detected by evaluating the transparency log. In order to determine if you have been affected: rm -r go.sum go.work.sum vendor/ && go mod tidy
Source: CVE Program / CVE List V5
CVSS Information
N/A
Source: CVE Program / CVE List V5
Vulnerability Type
N/A
Source: CVE Program / CVE List V5
Vulnerability Title
Google Go 加密问题漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
Google Go是美国Google公司开源的一款支持并发编程的脚本语言。 Google Go 1.25.13之前版本、1.26.0至1.26.6之前版本和1.27.0至1.27.0-rc.3之前版本，以及golang.org/x/mod/sumdb 0.40.0之前版本存在加密问题漏洞，该漏洞源于恶意GOSUMDB能够提供不在透明日志中的任意模块内容，可能导致攻击者通过协调的GOPROXY和GOSUMDB向客户端提供无法通过透明日志检测的恶意模块内容。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
Go toolchain cmd/go 0 ~ 1.25.13 -
golang.org/x/mod golang.org/x/mod/sumdb 0 ~ 0.40.0 -

II. Public POCs for CVE-2026-56864

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III. Intelligence Information for CVE-2026-56864

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Patches & Fixes for CVE-2026-56864 (2)

Vendor Advisories for CVE-2026-56864 (2)

News Coverage for CVE-2026-56864 (1)

IV. Related Vulnerabilities

Same product: cmd/go
Same vendor: Go toolchain

V. Comments for CVE-2026-56864

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