What’s Vulnerable › Vulnerabilities
CVE-2026-33811: Crash when handling long CNAME response in net
- Severity: high (CVSS 7.5 v3.1)
- Exploited in the wild: not listed in CISA KEV
- EPSS: 0.9% probability of exploitation in the next 30 days
- Public exploit or detection template: none known
- Published: 2026-05-07 · updated 2026-10-26
- Weakness: CWE-415
Description
When using LookupCNAME with the cgo DNS resolver, a very long CNAME response can trigger a double-free of C memory and a crash.
Affected products
- Go: before 1.25.10; from 1.26.0 before 1.26.3 — fixed in 1.25.10, 1.26.3
- Go Stdlib: before 1.25.10; from 1.26.0-0 before 1.26.3 — fixed in 1.25.10, 1.26.3
How to fix
Upgrade to a fixed version: Go 1.25.10, 1.26.3; Go Stdlib 1.25.10, 1.26.3. Check the vendor advisory for mitigations.
References
- https://go.dev/cl/767860
- https://go.dev/issue/78803
- https://groups.google.com/g/golang-announce/c/qcCIEXso47M
- https://pkg.go.dev/vuln/GO-2026-4981
- https://access.redhat.com/errata/RHSA-2026:22112
- https://access.redhat.com/errata/RHSA-2026:22120
- https://access.redhat.com/errata/RHSA-2026:22121
- https://access.redhat.com/errata/RHSA-2026:23262
- https://access.redhat.com/errata/RHSA-2026:23264
- https://access.redhat.com/errata/RHSA-2026:33120
- https://access.redhat.com/errata/RHSA-2026:33123
- https://access.redhat.com/errata/RHSA-2026:33142
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