# CVE-2026-75805: NULL Pointer Dereference in CMP Client Revocation Response Handling

> A malicious CMP server can cause a denial of service in OpenSSL clients using PKCS#10 CSRs for revocation by triggering a NULL pointer dereference.

- **Severity:** Medium 5.3 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 29 Sep 2026
- **Updated:** 29 Sep 2026
- **Also known as:** ALPINE-CVE-2026-75805, AZL-105369, AZL-105438, AZL-105477, AZL-105528, AZL-105591, AZL-105600, AZL-105717, AZL-105852, AZL-105891, BELL-CVE-2026-75805, CLEANSTART-2026-SF17865, DEBIAN-CVE-2026-75805, ECHO-738e-73da-1b38, GHSA-gpg3-m652-f2vc, MINI-2g29-ppf6-2gf8, UBUNTU-CVE-2026-75805

## What is CVE-2026-75805?

CVE-2026-75805 is a medium-severity vulnerability in Openssl Openssl, published on 29 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Issue summary: A CMP client that requests certificate revocation on the basis
of a PKCS#10 CSR may dereference a NULL pointer and terminate abnormally when
processing a crafted revocation response. 

Impact summary: The NULL pointer dereference happens on a read which 
leads to a crash and a Denial of Service for the affected client application.

CWE: CWE-476: NULL-pointer dereference

Description: A CMP client revoking a certificate has to tell the server which
certificate to revoke, and may do so by supplying a PKCS#10 CSR instead of the
certificate itself or its issuer name and serial number. This is
'openssl cmp -cmd rr -csr <file>' on the command line, or
OSSL_CMP_exec_RR_ses() with the certificate supplied via
OSSL_CMP_CTX_set1_p10CSR() through the API.

A CSR does not contain the issuer name and serial number of the certificate,
so the client does not send them. A server may optionally name the
certificate it revoked in its response, and the client then compares that
name against what it sent. Having sent neither an issuer name nor a serial
number, it has nothing to compare against, and a server returning a specially
crafted name causes the client to read from a NULL pointer and crash.

The revocation response is checked for valid message protection before
the affected code is reached, so an attacker must be a malicious or
compromised CMP server, or a man-in-the-middle in possession of the
secret used for message protection. Clients that identify the certificate
to be revoked by a certificate or by issuer and serial number rather
than by a PKCS#10 CSR are not affected.

FIPS impact: no
No FIPS modules are affected by this issue, as the CMP protocol
implementation is outside the OpenSSL FIPS module boundary.

Weakness: CWE-476 (NULL Pointer Dereference)

## Which versions are affected by CVE-2026-75805?

It affects 1 product.


Products: Openssl Openssl.

## How do I fix CVE-2026-75805?

Apply the vendor's patch.

## Is CVE-2026-75805 being exploited?

There is no known exploitation of CVE-2026-75805 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-2026-75805 and fix it if it is affected.

What it is: CVE-2026-75805 is a medium-severity vulnerability in Openssl Openssl, published on 29 Sep 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-2026-75805 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-2026-75805/ (Markdown: https://insights.sbomify.com/CVE-2026-75805/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-75805
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-75805
- OSV: https://osv.dev/vulnerability/CVE-2026-75805

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-75805/
Summaries are generated and may contain mistakes; the official description above is the record.