CVE-2026-39817: Invoking "go tool pack" does not sanitize output paths in cmd/go
Vulnerability summary
CVE-2026-39817 is a medium (CVSS 5.9) Out-of-bounds Write vulnerability in go toolchain cmd/go. EPSS estimates a 0.17% chance of exploitation in the next 30 days, higher than 6.3% of scored vulnerabilities.
Not severe (CVSS 5.9, local access); no exploitation reported by the 5 checked sources
Source freshness unavailable
How is this decided?Advisory lineage
Upstream 0 · Downstream 16 · Related 17Timeline
- 07-05-2026PublishedVulnerability first disclosed.
- 08-05-2026Last modifiedVulnerability information updated.
Description
The "go tool pack" subcommand (usually used only by the compiler as an internal tool with known-good inputs) does not sanitize output filenames. Extracting a malicious archive file with the "pack" subcommand can write files to arbitrary locations on the filesystem.
CVSS metrics
7 scores · 7 sources · 1 version- OSV · UbuntuEcosystem advisory · calculated5.9MediumCVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:C/C:N/I:H/A:N
- OSV · DebianEcosystem advisory · calculated5.9MediumCVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:C/C:N/I:H/A:N
- OSV · WolfiEcosystem advisory · calculated5.9MediumCVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:C/C:N/I:H/A:N
- OSV · ChainguardEcosystem advisory · calculated5.9MediumCVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:C/C:N/I:H/A:N
- NVDNIST5.9MediumCVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:C/C:N/I:H/A:N
- OSV · AlpineEcosystem advisory · calculated5.9MediumCVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:C/C:N/I:H/A:N
EPSS trend
Probability
0.17%
Chance of exploitation in the next 30 days
Percentile
6%
Versus all other CVEs
30-day change
Increase +0.01 pp
From 0.16% on 04-10-2026
Known exploited
Compare KEV catalogsNot in the CISA KEV catalog.
Not in the ENISA CNW catalog.
Not in the CIRCL catalog.
Public exploits
0 foundNo public exploits indexed.
Weaknesses
CWE · root causeAffected systems
Known conditions: local access, low-privilege account, user interaction (CVSS vector). Other conditions: not stated in public data.
Chainguard198 products
- aactl< 0.4.12-r50 | < 0.4.12-r51
- act< 0.2.88-r2
- actions-runner-controller-fips< 0.14.1-r1 | < 0.14.1-r2
- addon-resizer< 1.8.23-r19 | < 1.8.23-r18
- addon-resizer-fips< 1.8.23-r18
Alpine2 products
- go≥ 1.26.0, < 1.25.10-r0 | ≥ 1.26.0, < 1.26.3-r0
- rclone< 1.74.1-r0
2 vendors · 200 products · Showing 200 of 3395
References
13 links- pkg.go.devWEB