MediumCVE-2026-49844

    Apache Ant: Improper Encoding or Escaping of Output (CVE-2026-49844)

    Published

    What is affected, what to do

    Improper encoding of non-finite floating-point values during MapMessage JSON serialization in Apache Log4j API produces output that is not valid JSON. This issue affects Apache Log4j API versions 2.13.1 through 2.25.4 and version 2.26.0.

    An exploit is publicly available. Update Apache Log4j API to version 2.25.5, Apache Log4j API to version 2.26.1.

    Affected
    • Apache Log4j API lt 2.13.1..2.25.5
    • Apache Log4j API lt 2.26.0..2.26.1
    • Apache Log4j API lte 3.0.0-alpha1..3.0.0-beta2
    Fixed in
    • Apache Log4j API 2.25.5
    • Apache Log4j API 2.26.1

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

    Metrics

    6.3

    Priority

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

    Source: NVD, CVSS v4

    5.9

    CVSS v3

    Severity Medium on the scale from 0 to 10.

    0.8 %

    EPSS score

    Low — model estimates < 1% exploitation likelihood.

    Source: FIRST EPSS, percentile 56.3

    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
    84.98 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
    PoC (publicly reported)
    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
    6.3 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
    5.9
    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
    6.3
    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
    0.8 %
    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
    56.3
    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-116

    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

    Improper encoding of non-finite floating-point values during MapMessage JSON serialization in Apache Log4j API produces output that is not valid JSON. This issue affects Apache Log4j API versions 2.13.1 through 2.25.4 and version 2.26.0. The fix for CVE-2026-34481 did not cover all code paths: when a MapMessage contains a non-finite IEEE 754 value (NaN, Infinity, or -Infinity), MapMessage.asJson() emits the corresponding bare token. RFC 8259 does not permit these tokens, so a conformant parser rejects the resulting document. The defect is reachable only when both of the following conditions hold: * The application uses the message resolver https://logging.apache.org/log4j/2.x/manual/json-template-layout.html#event-template-resolver-message of JsonTemplateLayout or any other layout that relies on MapMessage.asJson() or MapMessage.getFormattedMessage(new String[]{"JSON"}). * The application logs a MapMessage that contains an attacker-controlled floating-point value. An attacker who can supply a non-finite value can cause the affected layout to emit malformed JSON, which may corrupt the enclosing log record or disrupt downstream log ingestion and parsing. Users are advised to upgrade to Apache Log4j API 2.25.5 or 2.26.1, both of which emit RFC 8259-compliant JSON for non-finite values.

    Source: BSI WID Portal

    Affected products

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

    Affected products
    VendorProductAffected versionsFixed in
    Apache Software FoundationApache Ant
    • 1.2 – < 1.10.18
    • 1.10.18
    Apache Software FoundationApache Log4j API
    • 2.13.1 – < 2.25.5
    • 2.26.0 – < 2.26.1
    • 3.0.0-alpha1 – ≤ 3.0.0-beta2
    • 2.25.5
    • 2.26.1
    • —
    Apache Software FoundationApache Neethi
    • < 3.2.3
    • 3.2.3
    Apache Software FoundationApache ZooKeeper
    • 3.8.0 – ≤ 3.8.6
    • 3.9.0 – ≤ 3.9.5
    • —
    • —
    FasterXMLjackson-databind
    • 2.0.0 – < 2.18.10
    • 2.19.0 – < 2.21.6
    • 2.22.0 – < 2.22.2
    • 3.0.0 – < 3.1.6
    • 3.2.0 – < 3.2.2
    • 2.18.10
    • 2.21.6
    • 2.22.2
    • 3.1.6
    • 3.2.2
    jhysoup
    • ≤ 1.23.1
    • —
    Oracle CorporationPrimavera P6 Enterprise Project Portfolio Management
    • 21.12.0.0 – ≤ 21.12.21.9
    • 22.12.0.0 – ≤ 22.12.21.4
    • 23.12.0 – ≤ 23.12.20
    • 24.12.0 – ≤ 24.12.16
    • 25.12.0 – ≤ 25.12.8
    • —
    • —
    • —
    • —
    • —
    Oracle CorporationPrimavera Unifier
    • 21.12.0 – ≤ 21.12.17
    • 22.12.0 – ≤ 22.12.15
    • 23.12.0 – ≤ 23.12.16
    • 24.12.0 – ≤ 24.12.16
    • 25.12.0 – ≤ 25.12.9
    • —
    • —
    • —
    • —
    • —
    SpringSpring Framework
    • 5.3.0 – < 5.3.49
    • 6.1.0 – < 6.1.28
    • 6.2.0 – < 6.2.18.1
    • 7.0.0 – < 7.0.7.1
    • 5.3.49
    • 6.1.28
    • 6.2.18.1
    • 7.0.7.1
    apacheant
    • < 1.10.18
    • 1.10.18
    apachelog4j
    • 2.13.1 – < 2.25.5
    • 2.26.0
    • 3.0.0
    • 2.25.5
    • —
    • —
    apacheneethi
    • < 3.2.3
    • 3.2.3
    apachezookeeper
    • 3.8.0 – < 3.8.7
    • 3.9.0 – < 3.9.6
    • 3.8.7
    • 3.9.6
    vmwarespring_framework
    • 5.3.0 – < 5.3.49
    • 6.1.0 – < 6.1.28
    • 6.2.0 – < 6.2.18.1
    • 7.0.0 – < 7.0.7.1
    • 5.3.49
    • 6.1.28
    • 6.2.18.1
    • 7.0.7.1
    ApacheAnt
    • < 1.10.18
    • 1.10.18
    Apachelog4j
    • < 2.25.5
    • < 2.26.1
    • 2.25.5
    • 2.26.1
    IBMQRadar SIEM
    • <7.5.0 UP15 IF06
    • —
    IBMSPSS
    • <19.0.0.0 IF034
    • —
    IBMWebSphere Application Server Liberty
    • < 26.0.0.10
    • < 26.0.0.9
    • 26.0.0.10
    • 26.0.0.9
    OracleCommerce
    • 11.4.0
    • —
    OracleCommunications
    • 11
    • 14
    • —
    • —
    From bundled advisories, not CVE-specific (32)

    Product list of a bundled advisory that does not state which product this CVE affects.

    Products from bundled advisories
    VendorProductAffected versionsFixed in
    AtlassianBamboo Data Center LTS
    • < 10.2.23
    • < 12.1.11
    • 10.2.23
    • 12.1.11
    AtlassianBamboo LTS
    • < 10.2.24
    • < 12.1.12
    • 10.2.24
    • 12.1.12
    AtlassianBitbucket
    • < 10.5.1
    • 10.5.1
    AtlassianBitbucket Data Center
    • < 10.4.2
    • < 10.4.3
    • 10.4.2
    • 10.4.3
    AtlassianBitbucket Data Center LTS
    • < 10.2.6
    • < 10.2.7
    • < 9.4.24
    • 10.2.6
    • 10.2.7
    • 9.4.24
    AtlassianBitbucket LTS
    • < 10.2.8
    • < 9.4.26
    • 10.2.8
    • 9.4.26
    AtlassianConfluence
    • < 11.0.0
    • 11.0.0
    AtlassianConfluence Data Center LTS
    • < 10.2.17
    • < 10.2.18
    • < 9.2.24
    • < 9.2.25
    • 10.2.17
    • 10.2.18
    • 9.2.24
    • 9.2.25
    AtlassianConfluence LTS
    • < 10.2.19
    • < 9.2.26
    • 10.2.19
    • 9.2.26
    AtlassianCrucible
    • < 4.9.14
    • < 4.9.15
    • 4.9.14
    • 4.9.15
    AtlassianFisheye
    • < 4.9.14
    • < 4.9.15
    • 4.9.14
    • 4.9.15
    AtlassianJira Data Center LTS
    • < 10.3.25
    • < 11.3.11
    • 10.3.25
    • 11.3.11
    AtlassianJira LTS
    • < 10.3.26
    • < 11.3.12
    • 10.3.26
    • 11.3.12
    AtlassianJira Service Management Data Center LTS
    • < 10.3.25
    • < 11.3.11
    • 10.3.25
    • 11.3.11
    RealObjectsPDFreactor
    • < 12.6.1
    • 12.6.1
    VMware TanzuSpring Framework
    • < 6.2.19
    • < 7.0.8
    • 6.2.19
    • 7.0.8

    Weakness classes (CWE)

    • CWE-116Improper Encoding or Escaping of Output

      Class

      The product prepares a structured message for communication with another component, but encoding or escaping of the data is either missing or done incorrectly. As a result, the intended structure of the message is not preserved.

      Entry at MITRE CWE-116

    Public exploit references

    Publicly reported proof-of-concepts, exploit modules and detection templates for this vulnerability. NEOSEC links to the original sources only and does not provide any exploit code.

    Public exploit references
    SourceReferenceMaturityPublished
    PoC-in-GitHub (nomi-sec)log4j-check (opens in a new tab)github.comPoC (publicly reported)reported, not verified

    References & sources

    • spring.iosecurity/cve-2026-41855
    • NVD (NIST)vuln/detail/CVE-2026-41855advisory
    • github.comspring-projects/spring-framework/commit/9bec52b1ec741976658e916…web
    • github.comspring-projects/spring-frameworkpackage
    • oracle.comOracle AdvisoryVendor advisory
    • lists.apache.orgthread/80xwwbhkqvbwkkmco6yl6fr5xkpdysjfVendor advisory
    • openwall.comlists/oss-security/2026/07/24/10
    • github.comGHSA-q4xh-88c3-wmh7Third-party advisory
    • github.comFasterXML/jackson-databind#6127Patch, Issue tracking
    • github.comFix commit (2.x line, forward-merged to the 2.21, 2.22 and 3.x branches)Patch
    • NVD (NIST)vuln/detail/CVE-2026-68497advisory
    • github.comFasterXML/jackson-databindpackage
    • github.comFasterXML/jackson-databind/releases/tag/jackson-databind-2.18.10web
    • github.comFasterXML/jackson-databind/releases/tag/jackson-databind-2.21.6web
    • github.comFasterXML/jackson-databind/releases/tag/jackson-databind-2.22.2web
    • github.comFasterXML/jackson-databind/releases/tag/jackson-databind-3.1.6web
    • github.comFasterXML/jackson-databind/releases/tag/jackson-databind-3.2.2web
    • lists.apache.orgthread/ohby1g6zjt72p0w79rhbr41nczzvr33yVendor advisory
    • openwall.comlists/oss-security/2026/09/15/7
    • NVD (NIST)vuln/detail/CVE-2026-84501web

    Linked CVEs

    Linked CVEs
    SeverityCVETitleCVSSExploitation
    MediumCVE-2026-91399Oracle Primavera P6 Enterprise Project Portfolio Management: security vulnerability4.3—
    MediumCVE-2026-91376Oracle Primavera P6 Enterprise Project Portfolio Management: security vulnerability6.5—
    MediumCVE-2026-84501Apache ZooKeeper: Operational log forgery via newline injection in EnsembleAuthenticationProvider5.3—
    HighCVE-2026-78254Apache Ant: Path traversal in ftp and scp tasks allows arbitrary file write7.4—
    HighCVE-2026-75140jsoup Uncontrolled Resource Consumption in XmlTreeBuilder7.5—
    HighCVE-2026-68497jackson-databind: Duration XMLGregorianCalendar Unbounded Number Parse DoS7.5—
    HighCVE-2026-66144Apache Neethi: Remote PolicyReference fetch lacks resource bounds7.5—
    MediumCVE-2026-49844Apache Log4j API: Improper serialization of non-finite floating-point values in MapMessage.asJson()5.9—
    CriticalCVE-2026-41855Spring Framework Unsafe Deserialization via Jackson JMS Converters9.8—
    HighCVE-2026-101736Oracle Primavera Unifier: security vulnerability7.4—
    HighCVE-2026-101735Oracle Primavera Unifier: security vulnerability7.1—
    MediumCVE-2026-101475Oracle Primavera Unifier: security vulnerability6.5—
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