# CVE-2026-42766: Possible NULL Dereference in Password-Based CMS Decryption

> An attacker can cause a denial of service by sending a crafted password-encrypted CMS message to applications using OpenSSL for decryption.

- **Severity:** Medium 5.9 (`CVSS:3.1/AV:N/AC:H/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:** ALPINE-CVE-2026-42766, AZL-89805, AZL-89867, AZL-89943, BELL-CVE-2026-42766, DEBIAN-CVE-2026-42766, GHSA-58mv-qqmv-gqgv, JLSEC-2026-1138, MINI-5vqv-cgr7-mvv6, MINI-hr9p-8rhg-74cq, UBUNTU-CVE-2026-42766

## What is CVE-2026-42766?

CVE-2026-42766 is a medium-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: A specially crafted password-encrypted CMS message
can trigger a NULL pointer dereference during CMS decryption.

Impact summary: This NULL pointer dereference leads to an application crash
and a Denial of Service.

The CMS PasswordRecipientInfo.keyDerivationAlgorithm field is defined as
OPTIONAL in the ASN.1 specification and may therefore be absent in specially
crafted inputs. During the password-based CMS decryption the OpenSSL
CMS implementation dereferences this field without first checking whether it
was present.

An attacker who supplies such a CMS message to an application performing
password-based CMS decryption can trigger an application crash, leading to
a Denial of Service.

Applications that process password-encrypted CMS messages may be affected.

The FIPS modules in 4.0, 3.6, 3.5, 3.4, and 3.0 are not 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-2026-42766?

It affects 1 product.


Products: Openssl Openssl.

## How do I fix CVE-2026-42766?

Apply the vendor's patch.

## Is CVE-2026-42766 being exploited?

There is no known exploitation of CVE-2026-42766 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-2026-42766 and fix it if it is affected.

What it is: CVE-2026-42766 is a medium-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-2026-42766 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-2026-42766/ (Markdown: https://insights.sbomify.com/CVE-2026-42766/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-42766
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-42766
- OSV: https://osv.dev/vulnerability/CVE-2026-42766

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-42766/
Summaries are generated and may contain mistakes; the official description above is the record.