# CVE-2026-42765: NULL Dereference in Certificate Verification with OCSP Checking

> Attackers can cause a denial of service in applications using OpenSSL if they enable specific non-default certificate verification flags.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **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-2026-42765, GHSA-vm8w-j6fw-jc7r, UBUNTU-CVE-2026-42765

## What is CVE-2026-42765?

CVE-2026-42765 is a high-severity vulnerability in Openssl Openssl, published on 9 Jun 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Issue summary: When a partial-chain certificate verification is enabled
together with OCSP response checking for the whole chain, a NULL dereference
will happen if the verified chain does not have a self-signed trusted anchor,
crashing the process.

Impact summary: A NULL pointer dereference can trigger a crash which leads to a
Denial of Service for an application.

When performing OCSP response checking for certificates in the verification
chain, the code always tries to access the next certificate as the issuer.
There is a check for a self-signed certificate. However with the partial
chain verification enabled when the chain does not have a self-signed trusted
anchor, the issuer will be NULL for the last certificate in the chain. A NULL
pointer dereference then happens.

This issue affects only applications which enable both OCSP verification
of the certificate chain (X509_V_FLAG_OCSP_RESP_CHECK_ALL) and partial
chain verification (X509_V_FLAG_PARTIAL_CHAIN) in the certificate
verification. Both flags are disabled by default. For that reason, we have
assigned Low severity to the issue.

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

Weakness: CWE-476 (NULL Pointer Dereference)

## Which versions are affected by CVE-2026-42765?

It affects 1 product.


Products: Openssl Openssl.

## How do I fix CVE-2026-42765?

Apply the vendor's patch.

## Is CVE-2026-42765 being exploited?

There is no known exploitation of CVE-2026-42765 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-2026-42765 and fix it if it is affected.

What it is: CVE-2026-42765 is a high-severity vulnerability in Openssl Openssl, published on 9 Jun 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-42765 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-2026-42765/ (Markdown: https://insights.sbomify.com/CVE-2026-42765/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-42765
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-42765
- OSV: https://osv.dev/vulnerability/CVE-2026-42765

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-42765/
Summaries are generated and may contain mistakes; the official description above is the record.