MediumCVE-2026-75805

NULL Pointer Dereference in CMP Client Revocation Response Handling (CVE-2026-75805)

Published 29.09.2026Last modified 08.10.2026Sources: SUSE, Debian, Ubuntu, Debian LTS, Red Hat, BSI, CVE.org, Msrc Update Guide

What is affected, what to do

Update OpenSSL to version 4.0.3, OpenSSL to version 3.6.5, OpenSSL to version 3.5.9.

Affected: OpenSSL lt 4.0.0..4.0.3
OpenSSL lt 3.6.0..3.6.5
OpenSSL lt 3.5.0..3.5.9
OpenSSL lt 3.4.0..3.4.8
OpenSSL lt 3.0.0..3.0.23
Fixed in: OpenSSL 4.0.3
OpenSSL 3.6.5
OpenSSL 3.5.9
OpenSSL 3.4.8
OpenSSL 3.0.23

Not sure whether and how you are affected? Ask a question about this vulnerability

Metrics

5.3

Priority

XIEM Effective CVSS: highest available CVSS rating from NVD and vendor data.

Source: Vendor (CNA), CVSS v3

5.3

CVSS v3

Severity Medium on the scale from 0 to 10.

Source: SUSE, Debian, Ubuntu, Debian LTS, Red Hat, BSI, CVE.org, Msrc Update Guide

0.3 %

EPSS score

Low — model estimates < 1% exploitation likelihood.

Source: FIRST EPSS, percentile 25.5

Show all metrics

Severity: Medium
Priority (0–325) The priority score is a consolidated metric that condenses several individual signals into a single, action-guiding ranking: technical severity (CVSS), exploitation likelihood (EPSS), known-exploited status (KEV) and the context of the affected asset. The aim is to answer the only truly important question in vulnerability management: what first? Read in glossary: 61.67 Methodology
Exploit maturity An exploit is code or a technique that specifically uses a concrete vulnerability to force unintended behaviour — such as executing code or escalating privileges. It is the tool that turns a theoretical flaw into a practical attack. Read in glossary: no public PoC known
XIEM Effective CVSS XIEM® is the tiered managed-security operating model from NEOSEC and a registered trademark of NEOSEC GmbH. It extends classic SIEM — the central collection, normalisation and correlation of security-relevant events — with endpoint forensics, network visibility and deception technology, and consolidates them into three building tiers: Sentry, Orchestrate and Command. Read in glossary: 5.3 Methodology
CVSS v3 CVSS is the globally established, open standard for assessing the technical severity of a vulnerability on a scale from 0 to 10. It describes how easily a flaw can be exploited and what damage it can cause — but not how likely its actual exploitation is. CVSS and the complementary EPSS deliberately answer different questions. Read in glossary: 5.3
EPSS score The EPSS score is the absolute model output for an individual vulnerability: the estimated probability of real-world exploitation within the next 30 days, expressed as a value between 0 and 1 (i.e. 0 % to 100 %). A score of 0.42 means „the model estimates a 42 % chance of real-world exploitation within 30 days“. Read in glossary: 0.3 %; Low — model estimates < 1% exploitation likelihood.
EPSS percentile The EPSS percentile is the relative position of a vulnerability within all EPSS-scored CVEs, expressed as a value between 0 and 1. A percentile of 0.90 means „this CVE has a higher EPSS score than 90 % of all other scored CVEs“. Unlike the EPSS score, it is not a probability — but a positioning within a ranking. Read in glossary: 25.5; Elevated — this CVE ranks above at least 10% of all CVEs scored today.
KEV status The KEV catalogue is a list maintained by the US authority CISA of vulnerabilities for which active exploitation in the wild has been confirmed. It answers not the question „how severe?“ but „is it already being attacked?“ — thereby sharply prioritising patching. Read in glossary: —
Published: 29.09.2026
CISA assessment (SSVC): Exploitation: none known · automatable · Technical impact: partial; Source: CISA Vulnrichment, as of 29 September 2026
CWE CWE is a catalogue of typical weakness types in software and hardware — such as flawed input validation, unsafe memory handling or poor authentication. Where a CVE names a concrete vulnerability in a concrete product, a CWE describes the underlying class of defect. Read in glossary: CWE-476

Detection rules

No NEOSEC detection rule is available for this vulnerability yet.

Classification under NIS2 and CRA

Rule-based classification from exploitation status and severity. It does not replace a case-by-case assessment.

NIS2 NIS2 is EU Directive (EU) 2022/2555 to raise the level of cybersecurity across the Union. It substantially broadens obligations compared with the first NIS directive: more sectors, mandatory risk management, staged reporting duties and personal accountability of senior management. Read in glossary: Handle the vulnerability in regular vulnerability handling under Art. 21(2)(e) NIS2.
CRA The CRA is EU Regulation (EU) 2024/2847 setting horizontal cybersecurity requirements for „products with digital elements“ — from industrial controllers and software to connected consumer devices. For the first time manufacturers must ensure security across the entire product lifecycle, handle vulnerabilities and provide security updates. Read in glossary: From 11.12.2027, Annex I Part II CRA requires manufacturers of affected products with digital elements to handle vulnerabilities without delay and provide security updates.
ISO/IEC 27001 ISO/IEC 27001 is the internationally leading standard for an information security management system (ISMS). It describes a risk-based, process-oriented framework to systematically plan, implement, review and improve information security. Read in glossary: Control A.8.8, management of technical vulnerabilities: assess relevance to your systems, plan remediation and keep evidence.

Description

A flaw was found in OpenSSL. When a Certificate Management Protocol (CMP) client requests certificate revocation using a PKCS#10 Certificate Signing Request (CSR), it omits the certificate issuer name and serial number. A malicious or compromised CMP server, or an attacker possessing valid message protection credentials, can exploit this flaw by returning a crafted revocation response. This triggers a NULL pointer dereference when the client attempts to compare response data, causing the client application to crash and resulting in a Denial of Service (DoS).

Source: suse_csaf, Debian Security Advisories, Ubuntu Security Notices, Debian LTS Advisories, redhat_csaf, BSI WID Portal, BSI CSAF, cvelistv5, NVD (NIST), Microsoft Security Update Guide

Affected products

The following versions are affected. Older releases of the same product line are also vulnerable unless stated otherwise.

Affected products
		Affected versions	Fixed in
OpenSSL	OpenSSL	`3.4.0 – < 3.4.8` `3.5.0 – < 3.5.9` `3.6.0 – < 3.6.5` `3.0.0 – < 3.0.23` `4.0.0 – < 4.0.3`	`3.4.8` `3.5.9` `3.6.5` `3.0.23` `4.0.3`
openssl	openssl	`4.0.0 – < 4.0.3` `3.5.0 – < 3.5.9` `3.0.0 – < 3.0.23` `3.6.0 – < 3.6.5` `3.4.0 – < 3.4.8`	`4.0.3` `3.5.9` `3.0.23` `3.6.5` `3.4.8`
Open Source	OpenSSL	`< 1.1.1zj` `< 1.0.2zs` `< 3.4.8` `< 3.6.5` `< 3.5.9` `< 3.0.23` `< 4.0.3`	`1.1.1zj` `1.0.2zs` `3.4.8` `3.6.5` `3.5.9` `3.0.23` `4.0.3`

Vendors and products

Affected operating systems

Affected operating systems

Linux	debian	openssl	`bookworm`
Linux	debian	openssl	`trixie`

Weakness classes (CWE)

CWE-476NULL Pointer Dereference
Base
The product dereferences a pointer that it expects to be valid but is NULL.
Entry at MITRE CWE-476

References & sources

openssl-library.orgOpenSSL AdvisoryVendor advisory
github.com4.0.3 git commitPatch
github.com3.6.5 git commitPatch
github.com3.5.9 git commitPatch
github.com3.4.8 git commitPatch

Changes to this CVE

Who changed this CVE and when: NVD (analysis, affected products, CVSS), the CVE publisher (CNA) and additional providers such as CISA (ADP).

08.10.2026Initial analysis by NVDNVD

Newly listed as affected:

OpenSSL (3.4.0 – before 3.4.8; 3.5.0 – before 3.5.9; 3.6.0 – before 3.6.5; 4.0.0 – before 4.0.3; 3.0.0 – before 3.0.23)

New references:

and 1 more reference

Show 6 original changes

Individual changes of this event as published by NVD
Type	Action	Before	After
Product configuration	added	—	OR cpe:2.3:a:openssl:openssl::::::::* versions from (including) 3.4.0 up to (excluding) 3.4.8 cpe:2.3:a:openssl:openssl::::::::* versions from (including) 3.5.0 up to (excluding) 3.5.9 cpe:2.3:a:openssl:openssl::::::::* versions from (including) 3.6.0 up to (excluding) 3.6.5 cpe:2.3:a:openssl:openssl::::::::* versions from (including) 4.0.0 up to (excluding) 4.0.3 cpe:2.3:a:openssl:openssl::::::::* versions from (including) 3.0.0 up to (excluding) 3.0.23
Reference type	added	—	OpenSSL Software Foundation: https://github.com/openssl/openssl/commit/7588db7fef14209c3caa3a101d11a02006b19166 Types: Patch
Reference type	added	—	OpenSSL Software Foundation: https://github.com/openssl/openssl/commit/7ca0ccb5172a577e9b87267d77bfe21e5481a5e7 Types: Patch
Reference type	added	—	OpenSSL Software Foundation: https://github.com/openssl/openssl/commit/9eb2a8a9b86136cdb39d6d7d50644dd66941cdc3 Types: Patch
Reference type	added	—	OpenSSL Software Foundation: https://github.com/openssl/openssl/commit/abf02872a4b71767ecc72293424420f5b009190f Types: Patch
Reference type	added	—	OpenSSL Software Foundation: https://openssl-library.org/news/secadv/20260929.txt Types: Vendor Advisory

Source identifier: nvd@nist.gov

29.09.2026Record modifiedCISA ADP

CVSS V3.1: AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

CISA assessment (SSVC): exploitation: none known, automatable: yes

Show 2 original changes

Individual changes of this event as published by NVD
Type	Action	Before	After
CVSS	added	—	AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
SSVC assessment	added	—	{"id":"CVE-2026-75805","role":"CISA Coordinator","options":[{"exploitation":"none"},{"automatable":"yes"},{"technicalImpact":"partial"}],"version":"2.0.3","timestamp":"2026-09-29T16:54:03.315064Z"}

Source identifier: 134c704f-9b21-4f2e-91b3-4a467353bcc0

29.09.2026Receivedopenssl.org

Weakness type: CWE-476

Description added or changed

New references:

and 1 more reference

Show 8 original changes

Individual changes of this event as published by NVD
Type	Action	Before	After
Description	added	—	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 type (CWE)	added	—	CWE-476
Affected versions (publisher)	added	—	New affected value received. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/75xxx/CVE-2026-75805.json">CVE-2026-75805</a>
Reference	added	—	https://github.com/openssl/openssl/commit/7588db7fef14209c3caa3a101d11a02006b19166
Reference	added	—	https://github.com/openssl/openssl/commit/7ca0ccb5172a577e9b87267d77bfe21e5481a5e7
Reference	added	—	https://github.com/openssl/openssl/commit/9eb2a8a9b86136cdb39d6d7d50644dd66941cdc3
Reference	added	—	https://github.com/openssl/openssl/commit/abf02872a4b71767ecc72293424420f5b009190f
Reference	added	—	https://openssl-library.org/news/secadv/20260929.txt

Source identifier: openssl-security@openssl.org

Embed badge

Show the severity and KEV status of this vulnerability on your site – with a link back here. The image is updated hourly.

<a href="https://intel.neosec.eu/en/cve/CVE-2026-75805"><img src="https://intel.neosec.eu/badge/cve/CVE-2026-75805.svg?lang=en" alt="CVE-2026-75805 – NEOSEC Intel" height="20"></a>