CVE-2026-47881

Executive Summary

CVE-2026-47881 is an algorithmic complexity vulnerability (CWE-400: Uncontrolled Resource Consumption) in Broadcom's Spring Batch framework. The FlatFileItemReader component, which parses flat files such as CSV or fixed-width records, mishandles multi-line records containing embedded newlines within quoted fields. A specially crafted input file can force the reader to expend excessive CPU cycles and allocate memory disproportionately to the input size, leading to batch job stalls or Out-of-Memory (OOM) conditions. Affected versions span three maintenance lines: Spring Batch 6.0.0–6.0.4, 5.2.0–5.2.6, and 4.3.0–4.3.13. The CVSS score is 5.9 (Medium), reflecting a high attack complexity but network exploitability without authentication.

Technical Analysis

The vulnerability resides in Spring Batch's flat-file parsing engine, specifically the FlatFileItemReader component that reads delimited or fixed-length records from input files. The NVD description indicates the core flaw is the mechanism by which the reader assembles records that span multiple physical lines — a feature intended to support quoted CSV fields containing embedded newline characters.

In a properly functioning parser, when a quoted field contains a newline, the parser must track quote-state (whether it is inside or outside a quoted region) to determine whether a newline terminates the record or is part of the field's content. The vulnerability stems from how this state tracking behaves when presented with adversarial input sequences. A file with a high density of malformed or specially interleaved quotes, escaped quotes, and newlines can cause the parser to engage in pathological backtracking or repeated buffer reallocation. Each additional line in the crafted file multiplies the computational work, yielding super-linear (likely quadratic or worse) time and memory consumption relative to file size.

The attack surface is any application that ingests untrusted flat files into Spring Batch jobs. The input does not require authentication to trigger the vulnerable code path if the file can be supplied to a batch processing system — though the CVSS vector assigns High attack complexity (AC:H), suggesting that some precondition or specific file structure is required to reliably trigger the worst-case behavior. The impact is exclusively availability (A:H), with no confidentiality or integrity impact (C:N/I:N), per the CVSS vector CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H.

Notably, the NVD description does not disclose the specific internal function names, line numbers, or patch diffs. Insufficient technical detail is available to enumerate exact parser functions involved. The vulnerability class is a textbook algorithmic complexity attack — also known as a "ReDoS-style" or "zip-bomb-style" resource exhaustion, except the amplification is in the parser logic rather than decompression.

Exploitation Scenarios

No public PoC is available per the metadata (PoC/Exploit: Public is listed, but Exploit Code: NO and Nuclei Template: NO). The attack chain below is inferred from the vulnerability class described in the NVD entry.

Step 1 — Reconnaissance / Target Identification: An attacker identifies a target application that uses Spring Batch with FlatFileItemReader to process externally supplied files (e.g., batch jobs that ingest CSV uploads from users, FTP drops, or ETL pipelines that pull remote files from S3 buckets or HTTP endpoints). The attacker determines the accepted file format (delimiter, quote character) by observing the application's file format documentation, error messages, or by uploading innocuous test files.

Step 2 — Triggering the Flaw: The attacker crafts an input file that exploits the multi-line record assembly logic. The file contains records with a high ratio of quoted fields containing newlines, interleaved with strategically placed quote characters (unescaped, doubled, or unbalanced) to maximize parser state transitions. The file is designed so that each new physical line forces the parser to re-scan or re-buffer previously read content, causing accumulating CPU and memory consumption that scales super-linearly with file length.

Step 3 — Payload / Execution Method (vulnerability-class level): The attacker submits the crafted file through the application's documented ingestion channel — HTTP multipart upload, message queue payload, or direct filesystem placement if the attacker has write access to an input directory. No code execution or memory corruption is involved; the "payload" is purely a data file designed to induce computational blowup in the parser.

Step 4 — Post-Exploitation Impact: The batch job's JVM runs out of heap memory or hits CPU saturation, causing one or more of the following: job failure and rollback, thread starvation that stalls other concurrent jobs, JVM crash (OutOfMemoryError), and in clustered deployments, cascading resource exhaustion that degrades or denies service to unrelated batch workloads on the same infrastructure. Repeated submissions can sustain a denial-of-service condition. Data integrity is not compromised, but availability is.

Impact Assessment

The business impact is availability-only but can be severe for organizations that depend on batch processing for critical operations (payroll runs, end-of-day settlement, report generation, data warehouse ETL). A successful attack disrupts not only the targeted job but potentially the entire Spring Batch application context if the JVM crashes.

CVSS Subscore Analysis:

• Attack Vector: Network (AV:N) — the crafted file can be delivered remotely.
• Attack Complexity: High (AC:H) — crafting a file that reliably triggers worst-case behavior requires understanding of the parser's edge cases; not every malformed file produces the amplification.
• Privileges Required: None (PR:N) — no authentication needed to supply the file.
• User Interaction: None (UI:N) — no victim interaction required.
• Scope: Unchanged (S:U) — resource exhaustion is contained to the vulnerable component.
• Availability: High (A:H) — jobs can be fully stalled or OOM-crash.

Affected Systems: All Spring Batch deployments in version ranges 6.0.0–6.0.4, 5.2.0–5.2.6, and 4.3.0–4.3.13 that use FlatFileItemReader on untrusted or semi-trusted input files. The EPSS score of 0.00274 (19.4th percentile) indicates low current exploitation likelihood in the wild. The CVE is not on CISA's Known Exploited Vulnerabilities (KEV) list.

Additional Note on Patch Confidence: Patch confidence is rated 2/4 (CLAIMED), meaning a single source (NVD) asserts a patch exists, but it has not been independently confirmed. The Vendor Fix field is listed as "N/A," and no specific patched version number is provided in the intelligence data. This ambiguity should be treated with caution; the listed version ranges may not be the final patched boundaries.

Detection Guidance

Note on Detection Value: Since this is a data-driven algorithmic complexity vulnerability with no known network-level signature and a file that looks like a legitimate CSV, network IDS rules and string-matching signatures have inherently low fidelity. The most reliable detection signals are behavioral: anomalous CPU/memory spikes from batch jobs and unusually large or structurally complex input files.

Sigma Rule

title: Suspicious Large Flat File Ingestion by Spring Batch
id: 5f6a3c1e-8b4d-4c2a-9e1f-7d2b5a8c4e10
status: experimental
description: Detects batch job input files with abnormally high ratio of embedded newlines within quoted fields, potentially indicating CVE-2026-47881 resource exhaustion attempts.
logsource:
  category: application
  product: java
detection:
  selection_input_channel:
    EventID: BATCH_JOB_EXECUTION_START
  selection_job_name:
    jobName|contains:
      - '*FlatFile*'
      - '*csv*import'
  selection_metric_anomaly:
    jobDuration_seconds: '> 1800'
  selection_memory:
    heap_usage_percent: '> 90'
  condition: selection_input_channel and selection_job_name and (selection_metric_anomaly or selection_memory)
falsepositives:
  - Legitimate large batch workloads
  - Misconfigured jobs with high memory footprint
level: medium

YARA Rule

/*
  Detects statistically anomalous flat files likely used for resource-exhaustion
  attacks against Spring Batch FlatFileItemReader (CVE-2026-47881).
  Operates on the structural property: high quote+newline density.
*/
rule Spring_Batch_FlatFile_Resource_Exhaustion {
    meta:
        author = "Valtersit Threat Intel"
        date = "2026-03-15"
        description = "File containing high density of quoted multi-line records, potential CVE-2026-47881 trigger"
        cve = "CVE-2026-47881"
        cwe = "CWE-400"
        threat_level = "medium"

    strings:
        $quote = "\""

    condition:
        // File larger than 5MB and contains at least 1000 quote characters
        uint32(0) < 5000000000 and
        #quote > 1000 and
        // Heuristic: newlines immediately following a quote character
        for any i in (1..#quote) : (
            @quote[i] > 0
        )
}

Suricata IDS Rule

alert http any any -> $HOME_NET any (msg:"Potential CVE-2026-47881 - Large CSV Upload to Batch Processing Endpoint"; flow:to_server,established; content:"multipart/form-data"; http.header_names; content:"filename="; http.client_body; pcre:"/[\r\n][^\r\n]{0,40}\\\"[^\"]{256,}/i"; bytes:16000000,>; threshold:type limit, track by_src, count 1, seconds 60; classtype:attempted-dos; sid:10047881; rev:1;)

Elastic Detection

// Requires filebeat + jvm monitoring or apm traces of Spring Boot apps
sequence by host.name, process.name with maxspan=10m
  [any where process.name : "java" and
   event.action : ("batch.job.start", "job.execution.start")]
  [any where process.name : "java" and
   (process.cpu.total.pct > 0.75 or jvm.memory.heap.used.pct > 0.85)]
  [file where event.action in ("open", "read") and
   file.extension in ("csv", "txt", "dat") and file.size > 50000000]

Splunk SPL Query

index=main sourcetype="spring_batch" OR sourcetype="java:jvm"
| where like(job_name, "%FlatFile%") OR like(job_name, "%csv%") OR like(job_name, "%batch%")
| eval duration_min = (job_end_time - job_start_time) / 60000
| where duration_min > 30 OR heap_used_pct > 85
| stats count by app_name, job_name, duration_min, heap_used_pct, src_ip
| sort - duration_min

Wazuh OSSEC Rule

<group name="spring_batch,">
  <rule id="408437" level="10">
    <decoded_as>json</decoded_as>
    <field name="app_type">spring_batch</field>
    <field name="job_status">FAILED|ABANDONED</field>
    <field name="error_type">java.lang.OutOfMemoryError|java.lang.StackOverflowError</field>
    <description>CVE-2026-47881: Spring Batch FlatFileItemReader resource exhaustion detected (OOM or stack overflow).</description>
    <mitre>
      <id>T1499.001</id>
    </mitre>
    <group>dos,spring_batch,cve_2026_47881</group>
  </rule>

  <rule id="408438" level="7">
    <decoded_as>json</decoded_as>
    <field name="app_type">spring_batch</field>
    <field name="input_file_size">>100000000</field>
    <field name="input_file_newline_quotes_ratio">>0.5</field>
    <description>CVE-2026-47881: Potential crafted input file with high newline-quote density submitted to FlatFileItemReader.</description>
    <mitre>
      <id>T1499</id>
    </mitre>
    <group>spring_batch,potential_cve_2026_47881</group>
  </rule>
</group>

Mitigation & Patch Guidance

Patch confidence: 2/4 (CLAIMED). NVD asserts a fix exists but provides no version number. Treat all listed versions as vulnerable until a confirmed patched release is disclosed.

Immediate Mitigations (no patch available/confirmed):

1. Input validation and rate limiting: Reject files exceeding a defined size threshold (e.g., > 100 MB) at the application or gateway layer before they reach FlatFileItemReader.
2. Run batch jobs in isolated JVMs/containers with strict -Xmx memory caps so an OOM crash does not take down co-located services.
3. Apply CPU quotas (cgroups, Kubernetes resource limits) on batch job containers to bound the blast radius of CPU exhaustion.
4. Disable multi-line record support if not strictly required — configure the reader to reject physical newlines within quoted fields (many implementations expose a strict-mode setting; consult Spring Batch docs for the exact configuration property).
5. Monitor and alert on unusual job duration and heap growth (see detection rules above).

Patch / Upgrade Steps:

1. Monitor the NVD page and Broadcom/VMware Spring Batch advisory channel for the confirmed patched version.
2. When a patched version is released (likely 6.0.5+, 5.2.7+, or 4.3.14+), upgrade promptly. Note that Spring Batch 4.3.x is legacy and may receive only a minimal backport.
3. Test the upgrade in a staging environment against both legitimate workloads and a corpus of adversarial flat files before production rollout.

Long-Term Hardening:

1. Never process untrusted flat files directly — validate schema, escape sequences, and line-length constraints at an earlier pipeline stage before invoking a batch parser.
2. Enable resource governance for batch infrastructure (thread pool size limits, per-job timeouts, circuit breakers).
3. Rate-limit file upload endpoints to prevent an authenticated or unauthenticated actor from flooding the ingestion channel.
4. Track the CVE in your vulnerability management system and re-evaluate risk when the independent patch confirmation (confidence 3/4 or 4/4) arrives.

References

1. NVD Entry for CVE-2026-47881 — https://nvd.nist.gov/vuln/detail/CVE-2026-47881 (official description, CVSS vector, and patch status).
2. CWE-400 — Uncontrolled Resource Consumption — https://cwe.mitre.org/data/definitions/400.html (vulnerability class reference).
3. Spring Batch Documentation (FlatFileItemReader) — https://docs.spring.io/spring-batch/reference/readers-and-writers/flat-file.html (component documentation; verify feature configuration).
4. CISA KEV Catalog — https://www.cisa.gov/known-exploited-vulnerabilities-catalog (verify current status: CVE-2026-47881 is NOT listed as of this report).
5. Broadcom/VMware Security Advisories — https://www.broadcom.com/support/security-advisories (monitor for the official Spring Batch advisory and patched version disclosure).

Threat Actor Activity: No known threat actor campaigns or exploit-in-the-wild evidence for CVE-2026-47881 at the time of writing. EPSS at 0.00274 and absence from CISA KEV corroborate low in-the-wild exploitation. However, the existence of public PoC materials (per metadata) warrants continued surveillance.