HighCVE-2026-34183

    Unbounded Memory Growth in the QUIC PATH_CHALLENGE Handler (CVE-2026-34183)

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

    What is affected, what to do

    A flaw was found in OpenSSL's QUIC PATH_CHALLENGE handler. A remote attacker can exploit this vulnerability by flooding a QUIC client or server with specially crafted PATH_CHALLENGE frames.

    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
    Fixed in
    • OpenSSL 4.0.1
    • OpenSSL 3.6.3
    • OpenSSL 3.5.7
    • OpenSSL 3.4.6

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

    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, SUSE, Ubuntu, BSI, Msrc Update Guide, CVE.org

    1.1 %

    EPSS score

    Moderate — model estimates 1-10% exploitation likelihood.

    Source: FIRST EPSS, percentile 64.1

    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
    89.09 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
    1.1 %
    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
    64.1
    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
    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-1325

    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's QUIC PATH_CHALLENGE handler. A remote attacker can exploit this vulnerability by flooding a QUIC client or server with specially crafted PATH_CHALLENGE frames. This leads to unbounded memory allocation within the local QUIC stack, as the system continuously allocates PATH_RESPONSE frames without them being acknowledged. The primary consequence is a Denial of Service (DoS), causing the affected application to terminate abnormally due to memory exhaustion.

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

    Affected products

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

    Affected products
    Affected versionsFixed in
    OpenSSLOpenSSL
    • 3.4.0 – < 3.4.6
    • 4.0.0 – < 4.0.1
    • 3.6.0 – < 3.6.3
    • 3.5.0 – < 3.5.7
    • 3.4.6
    • 4.0.1
    • 3.6.3
    • 3.5.7
    opensslopenssl
    • 3.6.0 – < 3.6.3
    • 3.5.0 – < 3.5.7
    • 3.4.0 – < 3.4.6
    • 4.0.0
    • 3.6.3
    • 3.5.7
    • 3.4.6
    • —
    IBMApp Connect Enterprise CD
    • < 13.4.0
    • 13.4.0
    IBMApp Connect Enterprise LTS
    • < 13.4.0
    • < 12.0.26
    • 13.4.0
    • 12.0.26
    Open SourceOpenSSL
    • < 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
    OracleSolaris
    • <11.3 ESU 36.36
    • <11.4 SRU 94
    • —
    • —

    Vendors and products

    Weakness classes (CWE)

    • CWE-1325Improperly Controlled Sequential Memory Allocation

      Base

      The product manages a group of objects or resources and performs a separate memory allocation for each object, but it does not properly limit the total amount of memory that is consumed by all of the combined objects.

      Entry at MITRE CWE-1325

    References & sources

    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).

    1. Initial analysis by NVDNVD

      Newly listed as affected:
      • OpenSSL (3.4.0 – before 3.4.6; 3.5.0 – before 3.5.7; 3.6.0 – before 3.6.3; 1 individual version)
      Show 6 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Product configurationadded
      —
      OR *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 typeadded
      —
      OpenSSL Software Foundation: https://github.com/openssl/openssl/commit/5b306efb0b3779dfdd0803b4afc9d08c91f11517 Types: Patch
      Reference typeadded
      —
      OpenSSL Software Foundation: https://github.com/openssl/openssl/commit/7d06955ebe0ecf8adfd4c1e92018586da47ef9ac Types: Patch
      Reference typeadded
      —
      OpenSSL Software Foundation: https://github.com/openssl/openssl/commit/d2e9efbe4900a373227deb136e8665401404ffac Types: Patch
      Reference typeadded
      —
      OpenSSL Software Foundation: https://github.com/openssl/openssl/commit/fbaa83859c01ad64f497b757aaf51be7d05ed9eb Types: Patch
      Reference typeadded
      —
      OpenSSL Software Foundation: https://openssl-library.org/news/secadv/20260609.txt Types: Vendor Advisory

      Source identifier: nvd@nist.gov

    2. Record modifiedCISA ADP

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

      Show the original change
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      CVSSadded
      —
      AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

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

    3. Record modifiedopenssl.org

      Show 8 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Referenceadded
      —
      https://github.com/openssl/openssl/commit/5b306efb0b3779dfdd0803b4afc9d08c91f11517
      Referenceadded
      —
      https://github.com/openssl/openssl/commit/7d06955ebe0ecf8adfd4c1e92018586da47ef9ac
      Referenceadded
      —
      https://github.com/openssl/openssl/commit/d2e9efbe4900a373227deb136e8665401404ffac
      Referenceadded
      —
      https://github.com/openssl/openssl/commit/fbaa83859c01ad64f497b757aaf51be7d05ed9eb
      Referenceremoved
      https://github.com/openssl/security/commit/5b306efb0b3779dfdd0803b4afc9d08c91f11517
      —
      Referenceremoved
      https://github.com/openssl/security/commit/7d06955ebe0ecf8adfd4c1e92018586da47ef9ac
      —
      Referenceremoved
      https://github.com/openssl/security/commit/d2e9efbe4900a373227deb136e8665401404ffac
      —
      Referenceremoved
      https://github.com/openssl/security/commit/fbaa83859c01ad64f497b757aaf51be7d05ed9eb
      —

      Source identifier: openssl-security@openssl.org

    One NVD translation into another language is hidden.

    Linked advisories

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