VulnerabilityPublished 14 Aug 2026

CVE-2026-55156: Token Optimizer MCP · Unauthenticated Path Traversal in Dashboard Session Log API Endpoints

Affects @ooples/token-optimizer-mcpSource GCVE Database

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Authoritative record:CVE-2026-55156· Medium 5.3

Not known to be exploited · CVSS 5.3 Medium : upgrade to 5.1.0 when convenient.

Data as of 13 Nov 2026, 23:54 UTC

CVSS 3.1 base score

5.3Medium

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

EPSS: 0.4% chance of exploitation in 30 days – higher than 39% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 5.1.0

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

t = 0 is the CVE’s publication on cve.org

Disclosed: evidence found.
CVE published 28 Sep 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: evidence found.
CISA SSVC: proof of concept public
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

CVE ID reserved
by GitHub, Inc.
16 Jun 202615:13 UTC, 104 days before disclosure
CVE published
on cve.org
28 Sep 202617:48 UTC, t = 0
CISA SSVC assessment
proof of concept public
28 Sep 202618:10 UTC, 22 minutes after disclosure
In Threat Radar
record ingested
26 Oct 202608:14 UTC, 28 days after disclosure

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), CISA SSVC, the Metasploit, Exploit-DB and nuclei-templates index as of 13 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

Upgrade @ooples/token-optimizer-mcp to 5.1.0.

Affected software

Product	Affected	Fixed in
npm@ooples/token-optimizer-mcp	Affected <5.1.0	Fixed in 5.1.0

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 in version 5.1.0. Until upgrading, it is recommended to validate the sessionId parameter strictly against an allowlist regex (e.g., /^[a-zA-Z0-9_-]{1,64}$/) to prevent directory traversal characters. Alternatively, applying path.basename to sessionId before path joining can mitigate traversal. Additionally, adding authentication middleware to all /api/* routes will prevent unauthenticated access to these endpoints.

Description

Token Optimizer MCP version prior to 5.1.0 contains an unauthenticated path traversal vulnerability in its dashboard session log API endpoints (/api/session-summary and /api/session-events). The endpoints accept a sessionId parameter that is directly concatenated into a filesystem path without proper sanitization, allowing attackers to read arbitrary .jsonl files on the server. This can expose sensitive session log data. The vulnerability has a CVSS score of 5.3 (medium severity) and is fixed in version 5.1.0.

Impact

An unauthenticated remote attacker can read arbitrary .jsonl files on the server filesystem that are reachable from the hooksDataPath directory via path traversal. This includes sensitive session logs containing tool invocations, hook outputs, and token usage data. The vulnerability allows information disclosure without requiring any credentials or privileges.

Summary

The dashboard HTTP server of @ooples/token-optimizer-mcp (version 5.0.1 and earlier) exposes two API endpoints, /api/session-summary and /api/session-events, that do not require authentication. Both endpoints take a sessionId query parameter which is concatenated unsafely into a filesystem path using path.join. Node.js normalizes '..' segments, enabling an attacker to perform path traversal and read any .jsonl file accessible to the server process. This was confirmed by a proof-of-concept showing unauthenticated retrieval of files outside the intended hooksDataPath directory. The flaw is categorized as CWE-22 (Improper Limitation of a Pathname to a Restricted Directory).

CWE-22Improper Limitation of a Pathname to a Restricted Directory (Path Traversal) (opens in a new tab)
Base weaknessLikelihood of exploit: HighCWE Top 25 (2025): #6OWASP Top 10 A01:2025: Broken Access Control (opens in a new tab)
The product uses external input to construct a pathname that is intended to identify a file or directory that is located underneath a restricted parent directory, but the product does not properly neutralize special elements within the pathname that can cause the pathname to resolve to a location that is outside of the restricted directory.
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.
Architecture and Design
For any security checks that are performed on the client side, ensure that these checks are duplicated on the server side, in order to avoid CWE-602. Attackers can bypass the client-side checks by modifying values after the checks have been performed, or by changing the client to remove the client-side checks…
Implementation · Input Validation
Inputs should be decoded and canonicalized to the application's current internal representation before being validated (CWE-180). Make sure that the application does not decode the same input twice (CWE-174).
OWASP Cheat Sheets
Authorization (opens in a new tab)
OWASP ASVS 4.0.3
V12.3.1 (opens in a new tab)
Attack patterns
Path Traversal (opens in a new tab)
Using Slashes and URL Encoding Combined to Bypass Validation Logic (opens in a new tab)
Manipulating Web Input to File System Calls (opens in a new tab)
Using Escaped Slashes in Alternate Encoding (opens in a new tab)
Using Slashes in Alternate Encoding (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

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What to do

Affected software

Description

AI analysisMachine-generated, updated 4 Nov 2026, 13:29 UTC

WeaknessesCWE-22

Technical details

References

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