VulnerabilityPublished 22 Sep 2026

CVE-2026-89407: FasterXML jackson-core · ReDoS

Affects FasterXML jackson-coreSource CVE Database V5

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Not known to be exploited · CVSS 7.5 High.

Data as of 6 Nov 2026, 23:24 UTC

CVSS 3.1 base score

7.5High

How severe the flaw is on the 0–10 CVSS scale.

EPSS: 0.6% chance of exploitation in 30 days – higher than 50% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Attack Vector: Network
Attack Complexity: Low
Privileges Required: None
User Interaction: None
Scope: Unchanged
Confidentiality: None
Integrity: None
Availability: High

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, up to and including the entire Internet. Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files to carry out an attack.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
Scope: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: None: There is no loss of confidentiality within the impacted component.
Integrity: None: There is no loss of integrity within the impacted component.
Availability: High: There is total loss of availability, resulting in the attacker being able to fully deny access to resources in the impacted component; this loss is either sustained (while the attacker continues to deliver the attack) or persistent (the condition persists even after the attack has completed). Alternatively, the attacker has the ability to deny some availability, but the loss of availability presents a direct, serious consequence to the impacted component (e.g., the attacker cannot disrupt existing connections, but can prevent new connections; the attacker can repeatedly exploit a vulnerability that, in each instance of a successful attack, leaks a only small amount of memory, but after repeated exploitation causes a service to become completely unavailable).

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 22 Sep 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 6 Nov 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Affected software

Product	Affected	Fixed in
FasterXMLjackson-core	Affected >=2.17.0 <=2.18.10 >=2.19.0 <=2.21.6 >=2.22.0 <=2.22.2	Fixed in–
FasterXMLjackson-core	Affected >=3.0.0 <=3.1.6 >=3.2.0 <=3.2.1	Fixed in–
MavenFasterXML/com.fasterxml.jackson.core:jackson-core`pkg:maven/FasterXML/com.fasterxml.jackson.core:jackson-core`Other threats	Affected >=2.17.0 <=2.18.10 >=2.19.0 <=2.21.6 >=2.22.0 <=2.22.2	Fixed in–
MavenFasterXML/tools.jackson.core:jackson-core`pkg:maven/FasterXML/tools.jackson.core:jackson-core`Other threats	Affected >=3.0.0 <=3.1.6 >=3.2.0 <=3.2.1	Fixed in–

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

A fix is available that replaces the inefficient regular expressions with a single-pass scanning approach. Users should upgrade jackson-core to a version later than the affected ranges specified. Until upgraded, consider limiting input sizes or disabling default String-to-number coercion if feasible. Patch status is confirmed by the description of the fix; no vendor advisory content was provided, so verify with official sources.

Description

CVE-2026-89407 is a high-severity vulnerability in FasterXML jackson-core affecting versions from 2.17.0 through 3.2.1 in specified subranges. It involves inefficient regular expression complexity in the NumberInput.looksLikeValidNumber() method, causing quadratic time complexity when processing certain numeric string inputs. This can lead to denial-of-service conditions by exhausting server resources during JSON deserialization of numeric types. The issue does not exist before version 2.17.0 and has been fixed by replacing the problematic regex with a single-pass scan.

Impact

An attacker able to supply JSON input to an application using affected jackson-core versions can cause denial-of-service by triggering excessive CPU consumption during numeric string validation. This can exhaust server request-handling threads, degrading availability. There is no direct confidentiality or integrity impact. The vulnerability affects applications that deserialize JSON numeric values using jackson-databind with default coercion settings.

Summary

The vulnerability arises from two regular expressions used in jackson-core's NumberInput.looksLikeValidNumber() method to pre-validate stringified numbers. The PATTERN_FLOAT regex contains adjacent quantifiers over the same character class, causing Java's regex engine to perform extensive backtracking on inputs that do not match, resulting in O(n^2) matching cost relative to input length. Attackers can exploit this by supplying large JSON numeric strings that trigger the regex during deserialization via jackson-databind's default String-to-number coercion. The default maxStringLength constraint (20 million characters) does not prevent this. Testing showed a 160,000-character input could consume about 74 seconds of CPU time in one call, enabling denial-of-service by exhausting server thread pools. The flaw is present starting from jackson-core 2.17.0 and fixed in later versions by replacing the regex with a more efficient scanning method.

CWE-1333Inefficient Regular Expression Complexity (opens in a new tab)
Base weaknessLikelihood of exploit: High
The product uses a regular expression with a worst-case computational complexity that is inefficient and possibly exponential.
Architecture and Design
Use regular expressions that do not support backtracking, e.g. by removing nested quantifiers.
System Configuration
Set backtracking limits in the configuration of the regular expression implementation, such as PHP's pcre.backtrack_limit. Also consider limits on execution time for the process.
Implementation
Do not use regular expressions with untrusted input. If regular expressions must be used, avoid using backtracking in the expression.
OWASP Cheat Sheets
File Upload (opens in a new tab)
OWASP ASVS 4.0.3
V12.1.1 (opens in a new tab)
Attack patterns
Regular Expression Exponential Blowup (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).
CWE-400Uncontrolled Resource Consumption (opens in a new tab)
Class weaknessLikelihood of exploit: High
The product does not properly control the allocation and maintenance of a limited resource.
MITRE discourages mapping vulnerabilities to this broad entry; the root cause is usually a more specific weakness.
Architecture and Design
Design throttling mechanisms into the system architecture. The best protection is to limit the amount of resources that an unauthorized user can cause to be expended. A strong authentication and access control model will help prevent such attacks from occurring in the first place.
Architecture and Design
Mitigation of resource exhaustion attacks requires that the target system either: recognizes the attack and denies that user further access for a given amount of time, or; uniformly throttles all requests in order to make it more difficult to consume resources more quickly than they can again be freed.
Architecture and Design
Ensure that protocols have specific limits of scale placed on them.
OWASP Cheat Sheets
File Upload (opens in a new tab)
OWASP ASVS 4.0.3
V12.1.1 (opens in a new tab)
Attack patterns
XML Ping of the Death (opens in a new tab)
Regular Expression Exponential Blowup (opens in a new tab)
Sustained Client Engagement (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

Community reviews

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 17 Oct 2026, 23:16 UTC

WeaknessesCWE-1333, CWE-400

Technical details

References

Community reviews

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