Vulnerability in tools.jackson.core:jackson-core (CVE-2026-18401)
Summary
Vulnerability in tools.jackson.core:jackson-core (CVE-2026-18401). Risk of unauthorized operations or information disclosure. Exploitable via maxNumberLength. Mitigation: upgrade to 3.1.0 or later.
Original description
The description as published by the source.
The non-blocking (asynchronous) JSON parser in jackson-core does not enforce the maxNumberLength constraint defined in StreamReadConstraints (default: 1000 characters). An attacker able to submit JSON to an application that uses the async parser API can supply a number token of arbitrary length, leading to excessive memory allocation and potential CPU exhaustion, resulting in a denial of service.
The synchronous parser enforces this limit correctly, so the constraint is applied inconsistently depending on which parsing API the application uses.
Root cause: the async parsing path in NonBlockingUtf8JsonParserBase and related classes never invokes the number length validation methods. Number parsing methods such as _finishNumberIntegralPart() accumulate digits into the TextBuffer without any length check, then call _valueComplete() to finalize the token. _valueComplete() does not call resetInt() or resetFloat(), which are the methods in ParserBase where validateIntegerLength() and validateFPLength() are performed. Because that validation step is skipped, maxNumberLength is never enforced on the async code path.
Impact: an attacker sending a JSON document containing an arbitrarily long number to an application using the async parser (for example a Spring WebFlux or other reactive application) can cause unbounded allocation in the TextBuffer and an OutOfMemoryError. If the application subsequently calls getBigIntegerValue() or getDecimalValue(), the JVM may additionally be tied…
Source: GitHub Security Advisories (Global) NVD GitHub Advisory
Auto-generated summary
Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.
A vulnerability tracked as CVE-2026-18401 has been found in tools.jackson.core:jackson-core.
Attackers can target a specific entry point like maxNumberLength over the network to misuse the product.
Risk of unauthorized operations or information disclosure.
What to do: upgrade tools.jackson.core:jackson-core to 3.1.0 or later.
If unsure, ask your IT team or search "tools.jackson.core:jackson-core CVE-2026-18401" on the vendor's site.
CVE-2026-18401 (tools.jackson.core:jackson-core) — CWE-770
Attack surface: maxNumberLength / StreamReadConstraints / NonBlockingUtf8JsonParserBase / _finishNumberIntegralPart
Patched: 3.1.0 — apply immediately
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.
A vulnerability (CWE-770) exists in tools.jackson.core:jackson-core. Attackers reach the vulnerable code path via maxNumberLength.
Check the vendor advisory for the affected versions of tools.jackson.core:jackson-core. Attack surface: maxNumberLength / StreamReadConstraints / NonBlockingUtf8JsonParserBase / _finishNumberIntegralPart.
Severity: ?. Risk of unauthorized operations or information disclosure.
Update to 3.1.0.
Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.
Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Audit SBOM/dependencies to find affected services.
Response actions
Concrete steps and command examples for SOC/SRE teams to execute in order
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1Identify exposure identify
Audit SBOM/dependencies for affected components.資産台帳・SBOM・依存マニフェストで tools.jackson.core:jackson-core を使っているサービスとバージョンを洗い出す。
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2Apply patch patch
Upgrade tools.jackson.core:jackson-core to 3.1.0ステージング環境で 3.1.0 に上げて回帰テスト → 本番反映。回帰テストはアプリの主要ハッピーパスを含めること。
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3Post-deployment verification verify
Confirm patched version is live in productionパッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。
Affected packages
Fix status by distribution
Fixed packages published by each distribution for this CVE
- Debian DEBIAN-CVE-2026-18401 jackson-core
- Ubuntu UBUNTU-CVE-2026-18401 jackson-core
References
- advisory github.com
- advisory nvd.nist.gov
- advisory github.com
- package github.com
- patch github.com
- patch github.com
- web github.com
- web github.com
- web repo.maven.apache.org