VulnerabilityPublished 1 Mar 2026Updated 2 Mar 2026

CVE-2026-3386: wren · Out-of-bounds Read

Affects wrenSource CVE Database V5

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Public exploit available · CVSS 4.8 Medium.

Data as of 31 Oct 2026, 08:20 UTC

CVSS 4.0 base score

4.8Medium

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

EPSS: 0.1% chance of exploitation in 30 days – higher than 9% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.

CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:P

Base metrics

Attack Vector: Local
Attack Complexity: Low
Attack Requirements: None
Privileges Required: Low
User Interaction: None
Vulnerable system confidentiality: None
Vulnerable system integrity: None
Vulnerable system availability: Low
Subsequent system confidentiality: None
Subsequent system integrity: None
Subsequent system availability: None

Threat metrics

Exploit Maturity: POC

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

Attack Vector: Local: The vulnerable system is not bound to the network stack and the attacker’s path is via read/write/execute capabilities. Either the attacker exploits the vulnerability by accessing the target system locally (e.g., keyboard, console), or through terminal emulation (e.g., SSH); or the attacker relies on User Interaction by another person to perform actions required to exploit the vulnerability (e.g., using social engineering techniques to trick a legitimate user into opening a malicious document).
Attack Complexity: Low: The attacker must take no measurable action to exploit the vulnerability. The attack requires no target-specific circumvention to exploit the vulnerability. An attacker can expect repeatable success against the vulnerable system.
Attack Requirements: None: The successful attack does not depend on the deployment and execution conditions of the vulnerable system. The attacker can expect to be able to reach the vulnerability and execute the exploit under all or most instances of the vulnerability.
Privileges Required: Low: The attacker requires privileges that provide basic capabilities that are typically limited to settings and resources owned by a single low-privileged user. Alternatively, an attacker with Low privileges has the ability to access only non-sensitive resources.
User Interaction: None: The vulnerable system can be exploited without interaction from any human user, other than the attacker.
Vulnerable system confidentiality: None: There is no loss of confidentiality within the Vulnerable System.
Vulnerable system integrity: None: There is no loss of integrity within the Vulnerable System.
Vulnerable system availability: Low: Performance is reduced or there are interruptions in resource availability. Even if repeated exploitation of the vulnerability is possible, the attacker does not have the ability to completely deny service to legitimate users. The resources in the Vulnerable System are either partially available all of the time, or fully available only some of the time, but overall there is no direct, serious consequence to the Vulnerable System.
Subsequent system confidentiality: None: There is no loss of confidentiality within the Subsequent System or all confidentiality impact is constrained to the Vulnerable System.
Subsequent system integrity: None: There is no loss of integrity within the Subsequent System or all integrity impact is constrained to the Vulnerable System.
Subsequent system availability: None: There is no impact to availability within the Subsequent System or all availability impact is constrained to the Vulnerable System.
Exploit Maturity: POC: Based on threat intelligence sources each of the following must apply: · Proof-of-concept is publicly available · No knowledge of reported attempts to exploit this vulnerability · No knowledge of publicly available solutions used to simplify attempts to exploit the vulnerability

Definitions: FIRST CVSS v4.0 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 1 Mar 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: evidence found.
CVSS exploit maturity: 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

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), CVSS vector, the Metasploit, Exploit-DB and nuclei-templates index as of 30 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.
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
wren-langwren	Affected 0.1 – 0.4.0 4 affected builds	Fixed in–
GitHubwren-lang/wren`pkg:github/wren-lang/wren`Other threats	Affected 0.1 – 0.4.0 4 affected builds	Fixed in–

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

AI-suggested

2) Employ strict access controls and sandboxing to limit the capabilities of local users and processes that can invoke wren-lang. 3) Monitor and audit usage of wren-lang binaries and related processes for unusual activity indicative of exploitation attempts. 4) Consider recompiling wren-lang from source with added bounds checking or applying community patches if available. 5) Isolate environments running wren-lang to prevent leakage of sensitive data to unauthorized users. 6) Stay informed on updates from the wren-lang project and apply official patches promptly once released. 7) For embedded or production systems, evaluate the necessity of wren-lang and remove or replace it if feasible to reduce attack surface. These targeted mitigations go beyond generic advice by focusing on access control, monitoring, and environment hardening specific to this local out-of-bounds read vulnerability.

Description

A flaw has been found in wren-lang wren up to 0.4.0. Affected by this vulnerability is the function emitOp of the file src/vm/wren_compiler.c. This manipulation causes out-of-bounds read. It is possible to launch the attack on the local host. The exploit has been published and may be used. The project was informed of the problem early through an issue report but has not responded yet.

Impact

The primary impact of CVE-2026-3386 is information disclosure through out-of-bounds memory reads. Organizations using wren-lang locally or embedded in applications may have sensitive data exposed, including potentially cryptographic keys, credentials, or proprietary information stored in memory adjacent to the vulnerable buffer. While the vulnerability does not allow remote exploitation or privilege escalation, local attackers or compromised users could leverage this flaw to gain intelligence that facilitates further attacks. This risk is particularly significant in multi-tenant or shared environments where local users have limited trust. The published exploit increases the likelihood of exploitation attempts. The absence of an official patch prolongs exposure, potentially affecting development environments, embedded devices, or software products relying on wren-lang. Overall, the impact is medium severity due to limited attack scope but meaningful confidentiality risks.

Summary

CVE-2026-3386 identifies a vulnerability in the wren-lang wren interpreter, versions 0.1 through 0.4.0, caused by an out-of-bounds read in the emitOp function located in src/vm/wren_compiler.c. The vulnerability arises from improper bounds checking during the compilation process, allowing the program to read memory outside the allocated buffer. This flaw can be triggered by a local attacker with limited privileges, as the attack vector requires local access but no elevated permissions or user interaction. The out-of-bounds read could lead to information disclosure, potentially leaking sensitive data from adjacent memory regions. Although the vulnerability does not directly allow code execution or privilege escalation, the exposure of memory contents can aid attackers in further exploitation or reconnaissance. An exploit has been published publicly, increasing the risk of exploitation. The CVSS 4.0 vector indicates low attack complexity and no user interaction, but limited to local attack vector and requiring low privileges. This vulnerability primarily affects environments where wren-lang is used locally, including embedded systems, development environments, or applications embedding the wren interpreter. The lack of a patch necessitates immediate mitigation to reduce risk.

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 9 Mar 2026, 01:21 UTC

Technical details

References

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