8.4

CVE-2026-56865: Fix transparency log tile verification bypass in golang.org/x/mod/sumdb/tlog

Awaiting analysis
AliasesUBUNTU-CVE-2026-56865DEBIAN-CVE-2026-56865CGA-224f-r9wf-3jjc
Published 13-08-2026Last modified 14-08-2026

Vulnerability summary

CVE-2026-56865 is a high (CVSS 8.4) vulnerability in go toolchain cmd/go. EPSS estimates a 0.13% chance of exploitation in the next 30 days, higher than 2.5% of scored vulnerabilities.

Priority
Routine

Not severe (CVSS 8.4, local access); no exploitation reported by the 5 checked sources

Source freshness unavailable

How is this decided?
CVSS score
8.4/10
010
High · v3.1 (CVE.org)
EPSS score
0.13%
0%100%
Low · 0.00 pp in 30 days
KEVNot listedNot listed by any tracked catalog.
RansomwareNot flaggedNo ransomware use recorded.
Public exploits0No public exploits recorded

Advisory lineage

Upstream 0 · Downstream 27 · Related 27
MGASA-2026-0341OPENSUSE-SU-2026:11516-1OPENSUSE-SU-2026:11517-1OPENSUSE-SU-2026:11536-1OPENSUSE-SU-2026:11575-1OPENSUSE-SU-2026:21592-1

Timeline

  1. 13-08-2026
    PublishedVulnerability first disclosed.
  2. 14-08-2026
    Last modifiedVulnerability information updated.

Description

A malicious GOPROXY was previously capable of forging up to two sumdb tiles that allow for a requested module to bypass the GOSUMDB check and persist attacker-controlled module content to a local Go module cache. This attack allows for a malicious GOPROXY to serve malicious module content that cannot be detected by evaluating the transparency log. All tiles are now correctly verified against their parents. In order to determine if you have been affected: rm -r go.sum go.work.sum vendor/ && go mod tidy

CVSS metrics

5 scores · 5 sources · 1 version

EPSS trend

Probability

0.13%

Chance of exploitation in the next 30 days

Percentile

3%

Versus all other CVEs

30-day change

No change 0.00 pp

From 0.13% on 04-10-2026

04-10-202603-11-2026

Known exploited

Compare KEV catalogs
CISA KEV

Not in the CISA KEV catalog.

ENISA CNW

Not in the ENISA CNW catalog.

CIRCL

Not in the CIRCL catalog.

Public exploits

0 found

No public exploits indexed.

Weaknesses

CWE · root cause

Affected systems

Version check

Known conditions: local access, no authentication, no user interaction (CVSS vector). Other conditions: not stated in public data.

Chainguard199 products
  • aactl< 0.4.12-r69
  • agentbeatAll versions (No fix recorded)
  • agentbeat-fipsAll versions (No fix recorded)
  • amazon-cloudwatch-agentAll versions (No fix recorded)
  • amazon-eks-amiAll versions (No fix recorded)
Alpine1 product
  • go< 1.26.8-r0

2 vendors · 200 products · Showing 200 of 1636

References

12 links
Show all 12 references