# CVE-2026-35188: Double-free When Checking OCSP Stapled Response

> A malicious server can trigger a double-free in OpenSSL clients via crafted OCSP stapled responses, causing denial of service or potential code execution.

- **Severity:** Medium 5.0 (`CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:L`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 9 Jun 2026
- **Updated:** 10 Jun 2026
- **Also known as:** DEBIAN-CVE-2026-35188, GHSA-vc8w-w49c-4jgj, UBUNTU-CVE-2026-35188

## What is CVE-2026-35188?

CVE-2026-35188 is a medium-severity use after free vulnerability in Openssl Openssl, published on 9 Jun 2026. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

Issue summary: A malicious server can exploit TLS OCSP stapling by delivering
a crafted response through the status_request extension, triggering a
double-free in the client's certificate verification path.

Impact summary: Successful exploitation allows an attacker to corrupt heap
memory via a double-free, potentially leading to a Denial of Service or
possibly an attacker controlled code execution or other undefined behavior.

If OCSP stapling is enabled and the TLS client connects to a malicious server,
a crafted OCSP stapled response can trigger a double free in the TLS client
when the stapled response is checked.

The OCSP stapling is not enabled by default. Reliable code execution
through a double-free is technically complex and highly environment-dependent
but the Denial of Service impact is straightforward to achieve, warranting
Moderate severity.

No FIPS modules are affected by this issue as the affected code is outside
the OpenSSL FIPS module boundary.

Weakness: CWE-415 (Double Free)

## Which versions are affected by CVE-2026-35188?

It affects 1 product.


Products: Openssl Openssl.

## How do I fix CVE-2026-35188?

Apply the vendor's patch.

## Is CVE-2026-35188 being exploited?

There is no known exploitation of CVE-2026-35188 in the wild and no public exploit code.

## Other vulnerabilities in Openssl Openssl

- [CVE-2009-3245](https://insights.sbomify.com/CVE-2009-3245/): Null dereference in n/a (critical 10.0)
- [CVE-2006-3738](https://insights.sbomify.com/CVE-2006-3738/): Memory corruption in n/a (critical 10.0)
- [CVE-2026-63073](https://insights.sbomify.com/CVE-2026-63073/): Untrusted Sender DN Used as Format String in CMP Response Validation (critical 9.8)
- [CVE-2016-6309](https://insights.sbomify.com/CVE-2016-6309/): Use after free in n/a (critical 9.8)
- [CVE-2016-0799](https://insights.sbomify.com/CVE-2016-0799/): Integer overflow in n/a (critical 9.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-35188 and fix it if it is affected.

What it is: CVE-2026-35188 is a medium-severity use after free vulnerability in Openssl Openssl, published on 9 Jun 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-35188 in the wild and no public exploit code.

Affected product: Openssl Openssl. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-35188/ (Markdown: https://insights.sbomify.com/CVE-2026-35188/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-35188
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-35188
- OSV: https://osv.dev/vulnerability/CVE-2026-35188

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-35188/
Summaries are generated and may contain mistakes; the official description above is the record.