Is CVE-2026-33818 exploited in the wild?

No. Junglewise Threat Intelligence has no report of CVE-2026-33818 being exploited in the wild.

How severe is CVE-2026-33818?

High severity, with a CVSS score of 7.5, published 13 August 2026.

Which products and versions are affected?

stdlib (Go) SEMVER:introduced=0,fixed=1.25.13,introduced=1.26.0-0,fixed=1.26.6,introduced=1.27.0-0,fixed=1.27.0-rc.3.

Is there a fix for CVE-2026-33818?

Yes. stdlib (Go): upgrade to 1.27.0-rc.3 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

How is CVE-2026-33818 attacked?

It is attacked over the network.

Am I affected by CVE-2026-33818?

Check whether you run stdlib (Go) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

CVE-2026-33818: Go Unmarshal stack exhaustion in recursive structure parsing

CVE-2026-33818 · Severity: high · CVSS 7.5 · Published 2026-08-13

Go's Unmarshal function, which parses structured data (such as JSON or XML) into program objects, is vulnerable to a denial-of-service attack when processing deeply-nested or recursive data structures. An attacker can craft malicious input that causes the parser to exhaust the call stack, crashing applications and disrupting service availability.

Technologies: stdlib (Go). Vendors: Go.

Quick answers

Is CVE-2026-33818 exploited in the wild?: No. Junglewise Threat Intelligence has no report of CVE-2026-33818 being exploited in the wild.
How severe is CVE-2026-33818?: High severity, with a CVSS score of 7.5, published 13 August 2026.
Which products and versions are affected?: stdlib (Go) SEMVER:introduced=0,fixed=1.25.13,introduced=1.26.0-0,fixed=1.26.6,introduced=1.27.0-0,fixed=1.27.0-rc.3.
Is there a fix for CVE-2026-33818?: Yes. stdlib (Go): upgrade to 1.27.0-rc.3 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-33818 attacked?: It is attacked over the network.
Am I affected by CVE-2026-33818?: Check whether you run stdlib (Go) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

How to fix

stdlib (Go): upgrade to 1.27.0-rc.3 or later
```
go get stdlib@v1.27.0-rc.3
```

Technical details

The vulnerability is a stack exhaustion flaw in Go's Unmarshal function, which lacks proper recursion limits when parsing deeply-nested or recursive data structures. An attacker can supply malformed input with excessive nesting depth that triggers unbounded recursion in the unmarshaling logic. The attack requires no authentication and is network-reachable if the application exposes an endpoint that accepts and unmarshals untrusted data. Successful exploitation results in a denial of service through stack overflow, crashing the affected application. The vulnerability has been addressed by enforcing recursion depth limits in the Unmarshal implementation.

Affected products

Go Go <1.23 (estimated)

Identifiers

CVE-2026-33818
GO-2026-5972

Timeline

2026-08-13: disclosed

References

This page as Markdown. Free to reuse under CC BY 4.0 with a link back.