# CVE-2026-34180: Heap Buffer Over-read in ASN.1 Content Parsing

> Attackers can cause denial of service or information disclosure via heap buffer over-read in OpenSSL's ASN.1 parser when processing crafted DER data.

- **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:** ALPINE-CVE-2026-34180, AZL-89796, AZL-89855, AZL-89940, BELL-CVE-2026-34180, CLEANSTART-2026-LF37646, DEBIAN-CVE-2026-34180, GHSA-3c8f-qq7h-7qv6, JLSEC-2026-1133, MINI-6qxv-32hh-x395, MINI-8mv2-hvr9-qw76, ROOT-OS-ALPINE-315-CVE-2026-34180, ROOT-OS-ALPINE-317-CVE-2026-34180, UBUNTU-CVE-2026-34180

## What is CVE-2026-34180?

CVE-2026-34180 is a high-severity memory corruption 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: Parsing a crafted DER-encoded ASN.1 structure with a primitive
element whose content exceeds 2 gigabytes in length may cause a heap buffer
over-read on 64-bit Unix and Unix-like platforms.

Impact summary: The heap buffer over-read may crash the application (Denial of
Service) or to load into the decoded ASN.1 object contents of memory beyond the
end of the input buffer.  More typically such ASN.1 elements would instead be
truncated.

An integer truncation in OpenSSL's ASN.1 decoder causes the content length of
an ASN.1 primitive element to be mishandled when it exceeds 2 gigabytes. In the
worst case the truncated length is treated as a request to scan the binary
content for a terminating zero byte, possibly causing OpenSSL to read either
less than or beyond the end of the allocated buffer.

Applications that pass attacker-supplied data to d2i_X509(), d2i_PKCS7(), or
any other d2i_* decoding function are affected. OpenSSL's own command-line
tools are not vulnerable, as data read through the BIO layer is checked before
it reaches the affected code. The issue only affects 64-bit Unix and Unix-like
platforms; 32-bit platforms and 64-bit Windows are not 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-125 (Out-of-bounds Read)

## Which versions are affected by CVE-2026-34180?

It affects 1 product.


Products: Openssl Openssl.

## How do I fix CVE-2026-34180?

Apply the vendor's patch.

## Is CVE-2026-34180 being exploited?

There is no known exploitation of CVE-2026-34180 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-2026-34180 and fix it if it is affected.

What it is: CVE-2026-34180 is a high-severity memory corruption 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-2026-34180 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-2026-34180/ (Markdown: https://insights.sbomify.com/CVE-2026-34180/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-34180
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-34180
- OSV: https://osv.dev/vulnerability/CVE-2026-34180

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-34180/
Summaries are generated and may contain mistakes; the official description above is the record.