HighCVE-2026-34180

Heap Buffer Over-read in ASN.1 Content Parsing (CVE-2026-34180)

Published 09.06.2026Last modified 23.07.2026Sources: Red Hat, Debian LTS, SUSE, Ubuntu, Debian, BSI, Msrc Update Guide, CVE.org

What is affected, what to do

A flaw was found in OpenSSL. An integer truncation vulnerability in the ASN.1 decoder can occur when processing a crafted DER-encoded ASN.1 structure with a primitive element exceeding 2 gigabytes.

Update OpenSSL to version 4.0.1, OpenSSL to version 3.6.3, OpenSSL to version 3.5.7.

Affected: OpenSSL lt 4.0.0..4.0.1
OpenSSL lt 3.6.0..3.6.3
OpenSSL lt 3.5.0..3.5.7
OpenSSL lt 3.4.0..3.4.6
OpenSSL lt 3.0.0..3.0.21
OpenSSL lt 1.1.1..1.1.1zh
OpenSSL lt 1.0.2..1.0.2zq
Fixed in: OpenSSL 4.0.1
OpenSSL 3.6.3
OpenSSL 3.5.7
OpenSSL 3.4.6
OpenSSL 3.0.21
OpenSSL 1.1.1zh
OpenSSL 1.0.2zq

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Metrics

7.5

Priority

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

Source: NVD, CVSS v3

7.5

CVSS v3

Severity High on the scale from 0 to 10.

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

1.0 %

EPSS score

Moderate — model estimates 1-10% exploitation likelihood.

Source: FIRST EPSS, percentile 63.4

Show all metrics

Severity: High
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: 88.39 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: 7.5 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: 7.5
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: 1.0 %; Moderate — model estimates 1-10% 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: 63.4; High — this CVE ranks above the median of all CVEs scored today (rank ≥ 36%).
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: 09.06.2026
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-125

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: High technical severity: assess and remediate the vulnerability in vulnerability handling under Art. 21(2)(e) NIS2 and document the decision.
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. An integer truncation vulnerability in the ASN.1 decoder can occur when processing a crafted DER-encoded ASN.1 structure with a primitive element exceeding 2 gigabytes. A remote attacker could exploit this to cause a heap buffer over-read. This may lead to an application crash, resulting in a Denial of Service (DoS), or potentially disclose sensitive information by loading memory contents beyond the input buffer. This issue primarily affects 64-bit Unix and Unix-like platforms.

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

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 – < 3.4.6` `3.0.0 – < 3.0.21` `4.0.0 – < 4.0.1` `3.6.0 – < 3.6.3` `1.0.2 – < 1.0.2zq` `1.1.1 – < 1.1.1zh` `3.5.0 – < 3.5.7`	`3.4.6` `3.0.21` `4.0.1` `3.6.3` `1.0.2zq` `1.1.1zh` `3.5.7`
openssl	openssl	`3.6.0 – < 3.6.3` `1.0.2 – < 1.0.2zq` `3.0.0 – < 3.0.21` `1.1.1 – < 1.1.1zh` `3.5.0 – < 3.5.7` `3.4.0 – < 3.4.6` `4.0.0`	`3.6.3` `1.0.2zq` `3.0.21` `1.1.1zh` `3.5.7` `3.4.6` —
IBM	App Connect Enterprise CD	`< 13.4.0`	`13.4.0`
IBM	App Connect Enterprise LTS	`< 13.4.0` `< 12.0.26`	`13.4.0` `12.0.26`
Open Source	OpenSSL	`< 3.4.6` `< 1.0.2zq` `< 4.0.1` `< 3.6.3` `< 3.0.21` `< 1.1.1zh`	`3.4.6` `1.0.2zq` `4.0.1` `3.6.3` `3.0.21` `1.1.1zh`
Oracle	Solaris	`<11.3 ESU 36.36` `<11.4 SRU 94`	— —
Splunk	Splunk Enterprise	`< 10.0.9` `< 10.2.6` `< 10.4.2` `< 9.4.14`	`10.0.9` `10.2.6` `10.4.2` `9.4.14`

Vendors and products

Affected operating systems

Affected operating systems

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

Weakness classes (CWE)

CWE-125Out-of-bounds Read
Base
The product reads data past the end, or before the beginning, of the intended buffer.
Entry at MITRE CWE-125

References & sources

openssl-library.orgOpenSSL AdvisoryVendor advisory
github.com4.0.1 git commitPatch
github.com3.6.3 git commitPatch
github.com3.5.7 git commitPatch
github.com3.4.6 git commitPatch
github.com3.0.21 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).

15.06.2026Initial analysis by NVDNVD

Newly listed as affected:

OpenSSL (1.0.2 – before 1.0.2zq; 1.1.1 – before 1.1.1zh; 3.0.0 – before 3.0.21; 3.4.0 – before 3.4.6; 3.5.0 – before 3.5.7; 3.6.0 – before 3.6.3; 1 individual version)

New references:

and 2 more references

Show 7 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) 1.0.2 up to (excluding) 1.0.2zq cpe:2.3:a:openssl:openssl::::::::* versions from (including) 1.1.1 up to (excluding) 1.1.1zh cpe:2.3:a:openssl:openssl::::::::* versions from (including) 3.0.0 up to (excluding) 3.0.21 cpe:2.3:a:openssl:openssl::::::::* versions from (including) 3.4.0 up to (excluding) 3.4.6 cpe:2.3:a:openssl:openssl::::::::* versions from (including) 3.5.0 up to (excluding) 3.5.7 cpe:2.3:a:openssl:openssl::::::::* versions from (including) 3.6.0 up to (excluding) 3.6.3 cpe:2.3:a:openssl:openssl:4.0.0:-::::::*
Reference type	added	—	OpenSSL Software Foundation: https://github.com/openssl/openssl/commit/1c6908e4fa5fa568752221d8eaf561a809751e5d Types: Patch
Reference type	added	—	OpenSSL Software Foundation: https://github.com/openssl/openssl/commit/cbe418ae978539cf14a398a207dba834c0e93e83 Types: Patch
Reference type	added	—	OpenSSL Software Foundation: https://github.com/openssl/openssl/commit/d93853c42110d6319e3df07842b488cb9f7ac5ff Types: Patch
Reference type	added	—	OpenSSL Software Foundation: https://github.com/openssl/openssl/commit/da5d62af75f69d6fbf7803743d7c56ac75461e43 Types: Patch
Reference type	added	—	OpenSSL Software Foundation: https://github.com/openssl/openssl/commit/f696c73c3e61b8c502d040af62e690c060908a16 Types: Patch
Reference type	added	—	OpenSSL Software Foundation: https://openssl-library.org/news/secadv/20260609.txt Types: Vendor Advisory

Source identifier: nvd@nist.gov

10.06.2026Record modifiedopenssl.org

New references:

and 1 more reference

Show 10 original changes

Individual changes of this event as published by NVD
Type	Action	Before	After
Reference	added	—	https://github.com/openssl/openssl/commit/1c6908e4fa5fa568752221d8eaf561a809751e5d
Reference	added	—	https://github.com/openssl/openssl/commit/cbe418ae978539cf14a398a207dba834c0e93e83
Reference	added	—	https://github.com/openssl/openssl/commit/d93853c42110d6319e3df07842b488cb9f7ac5ff
Reference	added	—	https://github.com/openssl/openssl/commit/da5d62af75f69d6fbf7803743d7c56ac75461e43
Reference	added	—	https://github.com/openssl/openssl/commit/f696c73c3e61b8c502d040af62e690c060908a16
Reference	removed	https://github.com/openssl/security/commit/1c6908e4fa5fa568752221d8eaf561a809751e5d	—
Reference	removed	https://github.com/openssl/security/commit/cbe418ae978539cf14a398a207dba834c0e93e83	—
Reference	removed	https://github.com/openssl/security/commit/d93853c42110d6319e3df07842b488cb9f7ac5ff	—
Reference	removed	https://github.com/openssl/security/commit/da5d62af75f69d6fbf7803743d7c56ac75461e43	—
Reference	removed	https://github.com/openssl/security/commit/f696c73c3e61b8c502d040af62e690c060908a16	—

Source identifier: openssl-security@openssl.org

One NVD translation into another language is hidden.

Linked advisories

@RISK®: The Consensus Security Vulnerability Alert: Vol. 26, Num. 25SANS @RISK25.06.2026

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