Answer in brief
CVE-2026-56865 records a Unknown severity vulnerability in Fix transparency log tile verification bypass in golang.org/x/mod/sumdb/tlog. The current sources do not mark it as known exploited. The current feed maps Go toolchain/cmd/go (generic), golang.org/x/mod/golang.org/x/mod/sumdb/tlog (generic), golang.org/x/mod (go), toolchain (go). Check affected ranges and fixed versions before updating.
Analysis pending evidence review
HOL Guard separates source facts from reviewed analysis. See the methodology.
A CVSS score is not reported in the current record. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.
Analysis status
Analysis pending evidence review
Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.
The current feed maps Go toolchain/cmd/go (generic), golang.org/x/mod/golang.org/x/mod/sumdb/tlog (generic), golang.org/x/mod (go), toolchain (go). Check affected ranges and fixed versions before updating.
| Package | Affected range | Fixed version |
|---|---|---|
| Go toolchain/cmd/gogeneric | >=0 <1.25.13 || >=1.26.0-0 <1.26.6 || >=1.27.0-0 <1.27.0-rc.3 | 1.25.13, 1.26.6, 1.27.0-rc.3 |
| golang.org/x/mod/golang.org/x/mod/sumdb/tloggeneric | >=0 <0.40.0 | 0.40.0 |
| golang.org/x/modgo | >=0 <0.40.0 | 0.40.0 |
| toolchaingo | >=0 <1.25.13 >=1.26.0-0 <1.26.6 >=1.27.0-0 <1.27.0-rc.3 | 1.25.13, 1.26.6, 1.27.0-rc.3 |
Published upstream
Aug 13, 2026
Evidence: source:cvelist:source_dates:source-dates:recordSource modified
Aug 13, 2026
Evidence: source:cvelist:source_dates:source-dates:recordFirst seen by HOL
Aug 13, 2026
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
Quoted source text, attributed separately from HOL analysis.
Answer in brief
CVE-2026-56865 records a Unknown severity vulnerability in Fix transparency log tile verification bypass in golang.org/x/mod/sumdb/tlog. The current sources do not mark it as known exploited. The current feed maps Go toolchain/cmd/go (generic), golang.org/x/mod/golang.org/x/mod/sumdb/tlog (generic), golang.org/x/mod (go), toolchain (go). Check affected ranges and fixed versions before updating.
Analysis pending evidence review
HOL Guard separates source facts from reviewed analysis. See the methodology.
A CVSS score is not reported in the current record. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.
Analysis status
Analysis pending evidence review
Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.
The current feed maps Go toolchain/cmd/go (generic), golang.org/x/mod/golang.org/x/mod/sumdb/tlog (generic), golang.org/x/mod (go), toolchain (go). Check affected ranges and fixed versions before updating.
| Package | Affected range | Fixed version |
|---|---|---|
| Go toolchain/cmd/gogeneric | >=0 <1.25.13 || >=1.26.0-0 <1.26.6 || >=1.27.0-0 <1.27.0-rc.3 | 1.25.13, 1.26.6, 1.27.0-rc.3 |
| golang.org/x/mod/golang.org/x/mod/sumdb/tloggeneric | >=0 <0.40.0 | 0.40.0 |
| golang.org/x/modgo | >=0 <0.40.0 | 0.40.0 |
| toolchaingo | >=0 <1.25.13 >=1.26.0-0 <1.26.6 >=1.27.0-0 <1.27.0-rc.3 | 1.25.13, 1.26.6, 1.27.0-rc.3 |
Published upstream
Aug 13, 2026
Evidence: source:cvelist:source_dates:source-dates:recordSource modified
Aug 13, 2026
Evidence: source:cvelist:source_dates:source-dates:recordFirst seen by HOL
Aug 13, 2026
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
Quoted source text, attributed separately from HOL analysis.