CVE-2026-39819: Invoking "go bug" follows symlinks in predictable temporary filenames in cmd/go
Vulnerability summary
CVE-2026-39819 is a medium (CVSS 5.3) vulnerability in go toolchain cmd/go. EPSS estimates a 0.18% chance of exploitation in the next 30 days, higher than 7.5% of scored vulnerabilities.
Not severe (CVSS 5.3, 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 bug" command writes to two files with predictable names in the system temporary directory (for example, "/tmp"). An attacker with access to the temporary directory can create a symlink in one of these names, causing "go bug" to overwrite the target of the symlink.
CVSS metrics
7 scores · 7 sources · 1 version- OSV · UbuntuEcosystem advisory · calculated5.3MediumCVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:H/A:N
- OSV · DebianEcosystem advisory · calculated5.3MediumCVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:H/A:N
- OSV · WolfiEcosystem advisory · calculated5.3MediumCVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:H/A:N
- OSV · ChainguardEcosystem advisory · calculated5.3MediumCVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:H/A:N
- NVDNIST5.3MediumCVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:H/A:N
- OSV · AlpineEcosystem advisory · calculated5.3MediumCVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:L/I:H/A:N
EPSS trend
Probability
0.18%
Chance of exploitation in the next 30 days
Percentile
8%
Versus all other CVEs
30-day change
Increase +0.03 pp
From 0.15% 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, no 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-r2 | < 0.14.1-r1
- 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