CVE-2026-33818 Go standard library CVE debrief

Who should care

Defenders responsible for systems using the Go standard library's encoding/asn1 package should assess exposure and implement compensating controls. This includes operators, platform administrators, vulnerability management teams, and security teams. They should review the supplied official advisory or CVE record to validate affected scope, severity, and vendor guidance.

Why it matters

CVE-2026-33818 is a high-severity vulnerability in the Go standard library's encoding/asn1 package that can lead to stack exhaustion. Defenders should assess exposure, implement compensating controls, and verify vendor remediation.

• Potential stack exhaustion leading to denial of service
• Need to verify affected versions and apply patches
• Importance of monitoring for potential exploitation attempts
• Limited information on exploitation or impact

Technical summary

The Go standard library's encoding/asn1 package has a vulnerability that allows for stack exhaustion when parsing deeply-nested, recursive structures. A recursion limit is enforced in Unmarshal to prevent this issue. Affected versions include 0, 1.25.13, 1.26.0-0, 1.26.6, and 1.27.0-0. The vulnerability can lead to potential stack exhaustion, and defenders should assess exposure and implement compensating controls. Defenders should prioritize assessing exposure and implementing compensating controls for systems using affected versions of the Go standard library's encoding/asn1 package.

Defensive priority

Defenders should prioritize assessing exposure and implementing compensating controls for systems using affected versions of the Go standard library's encoding/asn1 package.

Recommended defensive actions

• Assess exposure of systems using affected versions of the Go standard library's encoding/asn1 package
• Implement compensating controls to mitigate potential stack exhaustion
• Verify vendor remediation and apply patches for affected versions
• Monitor for potential exploitation attempts
• Review compensating controls for exposed systems while remediation is scheduled and verified
• Check relevant monitoring, detection, and logs for exposed assets that need extra review
• Track exceptions, retest remediated assets, and close the item only after evidence is documented

Evidence notes

The CVE record and source item provide details on the vulnerability, including its description and affected versions. However, additional information on exploitation or impact is limited. Defenders should verify vendor remediation and apply patches for affected versions. The encoding/asn1 package has a vulnerability that allows for stack exhaustion when parsing deeply-nested, recursive structures. A recursion limit is enforced in Unmarshal to prevent this issue.

Sources and references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.