VulnerabilityPublished 22 Oct 2026

CVE-2026-114348: webpack-dev-server · Generation of Error Message Containing Sensitive Information

Affects webpack-dev-serverSource CVE Database V5

Not known to be exploited · CVSS 5.3 Medium : upgrade to 6.1.0 or 5.2.7 when convenient.

Data as of 26 Oct 2026, 19:04 UTC

CVSS 3.1 base score

5.3Medium

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

EPSS

0.3% chance of exploitation in 30 days – higher than 23% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.

Exploitation: No evidence of active exploitation and no public proof of concept
Automatable: Attackers can reliably automate steps 1–4 of the kill chain
Technical impact: Limited control over the software or limited information exposure

CISA SSVC assessment, 2026-10-22.

Patch

Available – fixed in 6.1.0, 5.2.7

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

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

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: Low: There is some loss of confidentiality. Access to some restricted information is obtained, but the attacker does not have control over what information is obtained, or the amount or kind of loss is limited. The information disclosure does not cause a direct, serious loss to the impacted component.
Integrity: None: There is no loss of integrity within the impacted component.
Availability: None: There is no impact to availability within the impacted component.

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 22 Oct 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 webpack-dev-server to 6.1.0 or 5.2.7.

Affected software

Product	Affected	Fixed in
webpack-dev-serverwebpack-dev-server	Affected >=6.0.0 <6.1.0	Fixed in 6.1.0
webpack-dev-serverwebpack-dev-server	Affected >=5.1.0 <5.2.7	Fixed in 5.2.7
npmwebpack-dev-server`pkg:npm/webpack-dev-server`Other threats	Affected >=5.1.0 <5.2.7 >=6.0.0 <6.1.0	Fixed in 5.2.7 6.1.0

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

AI-suggested

Upgrade webpack-dev-server to version 5.2.7 or later, or 6.1.0 or later, where this issue is fixed. No other mitigation is required as the vulnerability is resolved in these versions.

Description

A vulnerability in webpack-dev-server versions 5.1.0 up to but not including 5.2.7, and 6.0.0 up to but not including 6.1.0, allows unauthenticated attackers to cause the server to disclose sensitive information via error messages. This occurs because the open-editor endpoint improperly validates the Host header, leading to an exception that reveals absolute filesystem paths, module locations, and source line numbers in HTTP 500 responses. The server continues running without denial of service. The issue is fixed in versions 5.2.7 and 6.1.0.

Impact

An unauthenticated network attacker able to reach the webpack-dev-server can send a specially crafted request that triggers an exception, causing the server to leak sensitive information in the error response. This information disclosure includes absolute filesystem paths and internal source details, which could aid further attacks or reconnaissance. There is no denial of service as the server continues running after the error. The CVSS v3.1 base score is 5.3 (medium severity), reflecting low confidentiality impact and no integrity or availability impact.

Summary

The webpack-dev-server's unauthenticated open-editor endpoint validates the Host header using a regular expression intended for browser Origin schemes. This validation can be bypassed by a Host value starting with 'file:' or an extension scheme, which circumvents hostname and allowedHosts checks. When such a malformed Host header is sent, the endpoint's URL construction throws an exception. In non-production mode, this results in an HTTP 500 response containing the full exception stack trace, disclosing sensitive internal information such as absolute filesystem paths, installed module locations, and source line numbers. The server remains operational after the error. This vulnerability is addressed in webpack-dev-server versions 5.2.7 and 6.1.0.

CWE-209Generation of Error Message Containing Sensitive Information (opens in a new tab)
Base weaknessLikelihood of exploit: HighOWASP Top 10 A10:2025: Mishandling of Exceptional Conditions (opens in a new tab)
The product generates an error message that includes sensitive information about its environment, users, or associated data.
Implementation
Ensure that error messages only contain minimal details that are useful to the intended audience and no one else. The messages need to strike the balance between being too cryptic (which can confuse users) or being too detailed (which may reveal more than intended).
Implementation
Handle exceptions internally and do not display errors containing potentially sensitive information to a user.
Implementation · Attack Surface Reduction
Use naming conventions and strong types to make it easier to spot when sensitive data is being used. When creating structures, objects, or other complex entities, separate the sensitive and non-sensitive data as much as possible.
OWASP Cheat Sheets
Error Handling (opens in a new tab)
Logging (opens in a new tab)
OWASP ASVS 4.0.3
V8.3.4 (opens in a new tab)
V14.3.3 (opens in a new tab)
V7.3.3 (opens in a new tab)
Attack patterns
Fuzzing for application mapping (opens in a new tab)
Padding Oracle Crypto Attack (opens in a new tab)
Query System for Information (opens in a new tab)
Blind SQL Injection (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).
CWE-1289Improper Validation of Unsafe Equivalence in Input (opens in a new tab)
Base weakness
The product receives an input value that is used as a resource identifier or other type of reference, but it does not validate or incorrectly validates that the input is equivalent to a potentially-unsafe value.
Implementation · Input Validation
Assume all input is malicious. Use an "accept known good" input validation strategy, i.e., use a list of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does.
OWASP Cheat Sheets
XML Security (opens in a new tab)
Mass Assignment (opens in a new tab)
OWASP ASVS 4.0.3
V13.3.1 (opens in a new tab)
V5.1.4 (opens in a new tab)
V5.1.3 (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 26 Oct 2026, 19:04 UTC

WeaknessesCWE-209, CWE-1289

Technical details

References

Community reviews

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