VulnerabilityPublished 4 Feb 2026

CVE-2026-23897: apollographql apollo-server · ReDoS

Affects apollographql apollo-serverSource CVE Database V5

Not known to be exploited · CVSS 7.5 High : upgrade to 5.4.0 or 4.13.0 soon.

Data as of 26 Oct 2026, 13:47 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 52% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 5.4.0, 4.13.0

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 4 Feb 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: 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 26 Oct 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.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, 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

Upgrade apollographql apollo-server to 5.4.0 or 4.13.0.

Affected software

Product	Affected	Fixed in
apollographqlapollo-server	Affected >=2.0.0 <=3.13.0 >=4.2.0 <4.13.0 >=5.0.0 <5.4.0	Fixed in 5.4.0 4.13.0

AI-suggested

European organizations should immediately audit their use of Apollo Server to determine if they use the startStandaloneServer default configuration in affected versions. If so, they should upgrade Apollo Server to versions later than 3.13.0, 4.13.0, or 5.4.0, where this vulnerability is resolved. If upgrading is not immediately feasible, organizations should consider migrating from standalone server usage to integration packages such as @as-integrations/express5 or @as-integrations/next, which are not affected by this vulnerability. Implementing Web Application Firewalls (WAFs) with rules to detect and block suspicious GraphQL requests containing exotic character set encodings can provide temporary protection. Rate limiting and IP reputation filtering can reduce the risk of DoS attacks. Monitoring server performance metrics and setting up alerts for unusual CPU spikes can help detect exploitation attempts early. Additionally, organizations should review their incident response plans to include scenarios involving GraphQL service disruptions. Finally, keeping dependencies up to date and subscribing to Apollo Server security advisories will help maintain ongoing protection.

Description

Apollo Server is an open-source, spec-compliant GraphQL server that's compatible with any GraphQL client, including Apollo Client. In versions from 2.0.0 to 3.13.0, 4.2.0 to before 4.13.0, and 5.0.0 to before 5.4.0, the default configuration of startStandaloneServer from @apollo/server/standalone is vulnerable to denial of service (DoS) attacks through specially crafted request bodies with exotic character set encodings. This issue does not affect users that use @apollo/server as a dependency for integration packages, like @as-integrations/express5 or @as-integrations/next, only direct usage of startStandaloneServer.

Impact

For European organizations, this vulnerability poses a significant risk of service disruption, particularly for those relying on Apollo Server in standalone mode to serve GraphQL APIs. Denial of service attacks can lead to downtime, impacting business operations, customer experience, and potentially causing financial losses. Sectors such as finance, e-commerce, telecommunications, and public services that increasingly adopt GraphQL for flexible API management are at risk. The vulnerability’s ease of exploitation without authentication means attackers can launch DoS attacks remotely, potentially from anywhere globally, increasing the threat surface. Additionally, organizations with strict uptime requirements or those providing critical services may face regulatory and reputational consequences if services are disrupted. Since the vulnerability does not affect integration package users, organizations using Apollo Server embedded in frameworks like Express or Next.js are less impacted, but those using the standalone server directly must prioritize mitigation. The lack of known exploits in the wild suggests a window for proactive defense, but the high CVSS score indicates urgency in addressing the issue.

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).

References

Community reviews

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 4 Feb 2026, 19:44 UTC

WeaknessesCWE-1333

Technical details

References

Community reviews

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