# CVE-2026-42771: Possible Out of Bounds Read in X509_VERIFY_PARAM_set1_email()

> An out-of-bounds read in OpenSSL's email validation can cause a crash, leading to denial of service during S/MIME message processing.

- **Severity:** Medium 6.2 (`CVSS:3.1/AV:L/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:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 9 Jun 2026
- **Updated:** 10 Jun 2026
- **Also known as:** GHSA-6fmj-jmjq-qcmg, UBUNTU-CVE-2026-42771

## What is CVE-2026-42771?

CVE-2026-42771 is a medium-severity memory corruption vulnerability in Openssl Openssl, published on 9 Jun 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

Issue summary: When the X509_VERIFY_PARAM_set1_email is called by an
application to validate a crafted e-mail address, such as during S/MIME
message validation, an out of bounds read can happen.

Impact summary: This out of bounds read will not directly exfiltrate
the data read to the attacker so the most likely result is a crash and
a Denial of Service.

An internal helper function called from X509_VERIFY_PARAM_[set|add]_email()
used a wrong length when validating the local part of an email address.
This could cause the 64 octet limit on the local part of an email address
to be not enforced, or cause an out of bound read and potentially a crash.

The bug is reachable via S-MIME validation with a crafted From: address
supplied in an email message that can potentially cause a crash.

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

Weakness: CWE-125 (Out-of-bounds Read)

## Which versions are affected by CVE-2026-42771?

It affects 1 product.


Products: Openssl Openssl.

## How do I fix CVE-2026-42771?

Apply the vendor's patch.

## Is CVE-2026-42771 being exploited?

There is no known exploitation of CVE-2026-42771 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-2026-42771 and fix it if it is affected.

What it is: CVE-2026-42771 is a medium-severity memory corruption vulnerability in Openssl Openssl, published on 9 Jun 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-42771 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-2026-42771/ (Markdown: https://insights.sbomify.com/CVE-2026-42771/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-42771
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-42771
- OSV: https://osv.dev/vulnerability/CVE-2026-42771

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-42771/
Summaries are generated and may contain mistakes; the official description above is the record.