LowCVE-2026-15310

    Python Software Foundation CPython: Uncontrolled Resource Consumption (CVE-2026-15310)

    Published Last modified Sources: SUSE, Debian LTS, CVE.org, OSV, Msrc Update Guide

    What is affected, what to do

    When decompressing crafted zip files using the bzip/LZMA/Zstandard compressions, Python could use an attacker-controlled size to pre-allocate memory, possibly resulting in memory exhaustion.

    Update Python Software Foundation CPython to version 3.10.22, Python Software Foundation CPython to version 3.11.17, Python Software Foundation CPython to version 3.12.15.

    Affected
    • Python Software Foundation CPython lt *..3.10.22
    • Python Software Foundation CPython lt 3.11.0..3.11.17
    • Python Software Foundation CPython lt 3.12.0..3.12.15
    • Python Software Foundation CPython lt 3.13.0..3.13.16
    • Python Software Foundation CPython lt 3.14.0..3.14.8
    • Python Software Foundation CPython lt 3.15.0a1..3.15.0rc2
    Fixed in
    • Python Software Foundation CPython 3.10.22
    • Python Software Foundation CPython 3.11.17
    • Python Software Foundation CPython 3.12.15
    • Python Software Foundation CPython 3.13.16
    • Python Software Foundation CPython 3.14.8
    • Python Software Foundation CPython 3.15.0rc2

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

    Metrics

    2.1

    Priority

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

    Source: Vendor (CNA), CVSS v4

    2.1

    CVSS v4

    Severity Low on the scale from 0 to 10.

    Source: SUSE, Debian LTS, CVE.org, OSV, Msrc Update Guide

    0.5 %

    EPSS score

    Low — model estimates < 1% exploitation likelihood.

    Source: FIRST EPSS, percentile 44.4

    Show all metrics
    Severity
    Low
    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
    50.77 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
    2.1 Methodology
    CVSS v4

    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
    2.1
    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
    0.5 %
    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
    44.4
    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
    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-400

    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

    When decompressing crafted zip files using the bzip/LZMA/Zstandard compressions, Python could use an attacker-controlled size to pre-allocate memory, possibly resulting in memory exhaustion.

    Source: suse_csaf, Debian LTS Advisories, cvelistv5, OSV (Open Source Vulnerabilities), 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 versionsFixed in
    Python Software FoundationCPython
    • 3.15.0a1 – < 3.15.0rc2
    • 3.13.0 – < 3.13.16
    • 3.14.0 – < 3.14.8
    • 3.12.0 – < 3.12.15
    • 3.11.0 – < 3.11.17
    • < 3.10.22
    • 3.15.0rc2
    • 3.13.16
    • 3.14.8
    • 3.12.15
    • 3.11.17
    • 3.10.22
    Distribution and container packages (4)

    Downstream packages (e.g. Bitnami, Debian, Ubuntu, Red Hat). Versions refer to the distribution, not the vendor.

    Distribution and container packages
    Affected versionsFixed in
    bitnamipython-min
    • 3.13.0
    • 3.12.0
    • 3.14.0
    • 3.11.0
    • —
    • —
    • —
    • —

    Vendors and products

    Affected operating systems

    Affected operating systems
    Linuxdebianpython3.11bookworm

    Weakness classes (CWE)

    • CWE-400Uncontrolled Resource Consumption

      Class

      The product does not properly control the allocation and maintenance of a limited resource.

      Entry at MITRE CWE-400

    References & sources

    • github.compython/cpython/pull/156003Patch
    • github.compython/cpython/issues/156002Issue tracking
    • mail.python.orgarchives/list/security-announce@python.org/thread/YUHXURX2WZGKG…Vendor advisory
    • github.compython/cpython/commit/f897dbf2f36a5935700b7c2d94d4681d2136b7d4Patch
    • NVD (NIST)vuln/detail/CVE-2026-15310web
    • github.compython/cpython/commit/1b424c0178a01e155fd0267dc28a8fc1159b33a8Patch
    • github.compython/cpython/commit/31980e84b9a708424a0a1dfecde3fc991e313f89Patch
    • github.compython/cpython/commit/e2311cfb3dd518f008f312fe0631f4f7490d237aweb, Patch
    • github.compython/cpython/commit/f507e6946a3194e83e1d7b8ee6e14567175e46defix, Patch
    • github.compython/cpython/commit/9d167992b59cf5e23c66b9ed742b13f5925f7d70fix, Patch
    • github.compython/cpython/commit/dcdd406ddbfc4cb29b24c3df17cbabe21d316ce1Patch
    • github.compython/cpython/commit/09a2e7e6678b4f65449e7ad8f112c48f944591e2Patch
    • github.compython/cpython/commit/6257029de42ef89b67f3d20137de87d43e197530fix, Patch
    • github.compython/cpython/commit/c2bfbcdd1a11690507a10bc0998f95b8dc6b6facfix, Patch

    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. Record modifiedpython.org

      1 individual change: Affected versions (publisher)

      Show the original change
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Affected versions (publisher)added
      —
      Affected value modified. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/15xxx/CVE-2026-15310.json">CVE-2026-15310</a>

      Source identifier: cna@python.org

    2. Record modifiedpython.org

      Show 2 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Referenceadded
      —
      https://github.com/python/cpython/commit/6257029de42ef89b67f3d20137de87d43e197530
      Referenceadded
      —
      https://github.com/python/cpython/commit/c2bfbcdd1a11690507a10bc0998f95b8dc6b6fac

      Source identifier: cna@python.org

    3. Record modifiedpython.org

      1 individual change: Affected versions (publisher)

      Show the original change
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Affected versions (publisher)added
      —
      Affected value modified. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/15xxx/CVE-2026-15310.json">CVE-2026-15310</a>

      Source identifier: cna@python.org

    4. Record modifiedpython.org

      Show the original change
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Referenceadded
      —
      https://github.com/python/cpython/commit/09a2e7e6678b4f65449e7ad8f112c48f944591e2

      Source identifier: cna@python.org

    5. Record modifiedpython.org

      Show the original change
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Referenceadded
      —
      https://github.com/python/cpython/commit/dcdd406ddbfc4cb29b24c3df17cbabe21d316ce1

      Source identifier: cna@python.org

    Show 8 older changes

    1. Record modifiedpython.org

      Show the original change
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Referenceadded
      —
      https://github.com/python/cpython/commit/9d167992b59cf5e23c66b9ed742b13f5925f7d70

      Source identifier: cna@python.org

    2. Record modifiedpython.org

      Show the original change
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Referenceadded
      —
      https://github.com/python/cpython/commit/f507e6946a3194e83e1d7b8ee6e14567175e46de

      Source identifier: cna@python.org

    3. Record modifiedpython.org

      Show the original change
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Referenceadded
      —
      https://github.com/python/cpython/commit/e2311cfb3dd518f008f312fe0631f4f7490d237a

      Source identifier: cna@python.org

    4. Record modifiedpython.org

      Show the original change
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Referenceadded
      —
      https://github.com/python/cpython/commit/31980e84b9a708424a0a1dfecde3fc991e313f89

      Source identifier: cna@python.org

    5. Record modifiedpython.org

      1 individual change: Affected versions (publisher)

      Show the original change
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Affected versions (publisher)added
      —
      Affected value modified. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/15xxx/CVE-2026-15310.json">CVE-2026-15310</a>

      Source identifier: cna@python.org

    6. Record modifiedpython.org

      Show the original change
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Referenceadded
      —
      https://github.com/python/cpython/commit/1b424c0178a01e155fd0267dc28a8fc1159b33a8

      Source identifier: cna@python.org

    7. Record modifiedCISA ADP

      CISA assessment (SSVC): exploitation: none known, automatable: no

      Show the original change
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      SSVC assessmentadded
      —
      {"id":"CVE-2026-15310","role":"CISA Coordinator","options":[{"exploitation":"none"},{"automatable":"no"},{"technicalImpact":"partial"}],"version":"2.0.3","timestamp":"2026-08-25T15:34:06.442859Z"}

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

    8. Receivedpython.org

      CVSS V4.0: AV:N/AC:L/AT:P/PR:N/UI:A/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N

      Weakness type: CWE-400

      Description added or changed

      Show 7 original changes
      Individual changes of this event as published by NVD
      TypeActionBeforeAfter
      Affected versions (publisher)added
      —
      CPython
      Descriptionadded
      —
      When decompressing crafted zip files using the bzip/LZMA/Zstandard compressions, Python could use an attacker-controlled size to pre-allocate memory, possibly resulting in memory exhaustion.
      CVSSadded
      —
      AV:N/AC:L/AT:P/PR:N/UI:A/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
      Weakness type (CWE)added
      —
      CWE-400
      Referenceadded
      —
      https://github.com/python/cpython/issues/156002
      Referenceadded
      —
      https://github.com/python/cpython/pull/156003
      Referenceadded
      —
      https://mail.python.org/archives/list/security-announce@python.org/thread/YUHXURX2WZGKGNA4ANYBQS2VZRYQ5JNK/

      Source identifier: cna@python.org

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