OpenTofu has high CPU usage when using K8S remote state backend or when parsing specifically crafted TLS certificates from untrusted or compromised servers

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### Impact Unauthenticated denial of service. ### Summary When OpenTofu performs requests against an untrusted (or compromised) third-party server or connects to an attacker-controlled server, the initial connection negotiation can produce high CPU usage, leading to possible denial of service. These vulnerabilities **do not** permit arbitrary code execution or allow disclosure of confidential information. ### Details OpenTofu relies on third-party implementations of TLS certificate verification and HTTP request execution from the standard library of the Go programming language. The Go project has recently published the following advisories for those implementations which indirectly affect OpenTofu's behavior: - [CVE-2026-42504](https://www.cve.org/CVERecord?id=CVE-2026-42504): Quadratic complexity in WordDecoder.DecodeHeader in mime - [CVE-2026-27145](https://www.cve.org/CVERecord?id=CVE-2026-27145): Inefficient candidate hostname parsing in crypto/x509 CVE-2026-42504 affects OpenTofu's K8S remote state implementation. The operator of a configuration that uses such a backend needs to double-check the trustworthiness of the server used for this purpose. In situations where the server is untrusted or compromised, an attacker could configure it to respond with an intentionally crafted HTTP response designed to target this specific vulnerability in the Go standard library, potentially leading to high CPU usage. CVE-2026-27145 has a similar outcome: if an untrusted or compromised third-party server is used, an attacker could craft a specific TLS certificate that targets this vulnerability in the Go standard library, which could also lead to high CPU usage. Typical use of OpenTofu already requires caution in selection of third-party dependencies. ### Patches OpenTofu v1.11.9 and v1.12.2 address these vulnerabilities by upgrading to the Go versions that fix them (v1.25.11 and v1.26.3). The OpenTofu v1.10 series is also impacted by these vulnerabilities. However, that series is built with a version of Go for which no upstream fix is available. Adopting Go 1.25.11 for that series would effectively end support for certain versions of macOS and Linux, and the OpenTofu Project has determined that the impact of these vulnerabilities is not high enough to justify that disruption in a patch release. For those using OpenTofu v1.10 releases, we recommend planning an upgrade to OpenTofu v1.11.9 in the near future.

Source published

20 Aug 2026 18:36:22 UTC

Source modified

10 Sep 2026 03:51:12 UTC

Saved here

24 Oct 2026 13:19:41 UTC

Source terms

GitHub Advisory Database · CC-BY-4.0

Original source record · Cite this exact observation · Complete original publisher JSON

Source: osv · GitHub Advisory Database · CC-BY-4.0. The publisher's wording is preserved. ChangeIntel groups the information and labels changes. The JSON record includes additional source fields.

CVSS_V3 · CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:U/C:N/I:N/A:L

Publisher rating · LOW

OpenTofu has high CPU usage when using K8S remote state backend or when parsing specifically crafted TLS certificates from untrusted or compromised servers in github.com/opentofu/opentofu

Source published

25 Aug 2026 19:43:10 UTC

Source modified

26 Aug 2026 01:19:18 UTC

Saved here

24 Oct 2026 13:19:41 UTC

Source terms

OSV · upstream source license applies

Original source record · Cite this exact observation · Complete original publisher JSON

Source: osv · OSV · upstream source license applies. The publisher's wording is preserved. ChangeIntel groups the information and labels changes. The JSON record includes additional source fields.