CVE-2026-33811 — HIGH (7.5)

Q: What is CVE-2026-33811?

CVE-2026-33811 is a vulnerability with a CVSS score of 7.5 (HIGH). When using LookupCNAME with the cgo DNS resolver, a very long CNAME response can trigger a double-free of C memory and a crash.

Q: How severe is CVE-2026-33811?

CVE-2026-33811 has been rated HIGH with a CVSS base score of 7.5/10. Review the CVSS metrics above for detailed severity breakdown.

Q: Is there a patch for CVE-2026-33811?

Check the references section above for vendor advisories and patch information. Affected products include: Golang Go.

Vulnerability 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.

CVSS Score

7.5

HIGH

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Attack Vector

NETWORK

Attack Complexity

LOW

Privileges Required

NONE

User Interaction

NONE

Scope

UNCHANGED

Confidentiality

NONE

Integrity

NONE

Availability

HIGH

Affected Products

Vendor	Product	Versions
Golang	Go	< 1.25.10

Related Weaknesses (CWE)

CWE-415

References

https://go.dev/cl/767860Patch
https://go.dev/issue/78803Issue Tracking
https://groups.google.com/g/golang-announce/c/qcCIEXso47MMailing ListThird Party Advisory
https://pkg.go.dev/vuln/GO-2026-4981Vendor Advisory

FAQ

What is CVE-2026-33811?

CVE-2026-33811 is a vulnerability with a CVSS score of 7.5 (HIGH). When using LookupCNAME with the cgo DNS resolver, a very long CNAME response can trigger a double-free of C memory and a crash.

How severe is CVE-2026-33811?

CVE-2026-33811 has been rated HIGH with a CVSS base score of 7.5/10. Review the CVSS metrics above for detailed severity breakdown.

Is there a patch for CVE-2026-33811?

Check the references section above for vendor advisories and patch information. Affected products include: Golang Go.