VulnerabilityPublished 22 Feb 2026Updated 23 Feb 2026

CVE-2026-2940: Zaher1307 tiny_web_server · Out-of-bounds Write

Affects Zaher1307 tiny_web_serverSource CVE Database V5

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Public exploit available · CVSS 6.9 Medium.

Data as of 29 Oct 2026, 19:04 UTC

CVSS 4.0 base score

6.9Medium

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

EPSS: 0.3% chance of exploitation in 30 days – higher than 31% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.

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

Base metrics

Attack Vector: Network
Attack Complexity: Low
Attack Requirements: None
Privileges Required: None
User Interaction: None
Vulnerable system confidentiality: Low
Vulnerable system integrity: Low
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: Network: The vulnerable system is bound to the network stack and the set of possible attackers extends beyond the other options listed below, 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: 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: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files of the vulnerable system to carry out an attack.
User Interaction: None: The vulnerable system can be exploited without interaction from any human user, other than the attacker.
Vulnerable system 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 Vulnerable System.
Vulnerable system integrity: Low: Modification of data is possible, but the attacker does not have control over the consequence of a modification, or the amount of modification is limited. The data modification does not have a direct, serious impact to 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 22 Feb 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 29 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
Zaher1307tiny_web_server	Affected =8d77b1044a0ca3a5297d8726ac8aa2cf944d481b	Fixed in–

AI-suggested

To mitigate CVE-2026-2940 effectively, organizations should first identify all deployments of tiny_web_server within their environment, including embedded devices and IoT systems. 2) Employ intrusion detection and prevention systems (IDS/IPS) with signatures or anomaly detection capable of identifying suspicious requests targeting URL handlers. 3) If feasible, replace tiny_web_server with alternative, actively maintained web servers that have robust security track records. 4) Monitor public repositories and vendor communications closely for any forthcoming patches or updates and apply them promptly. 5) Conduct thorough code reviews and testing if custom modifications exist, to identify and remediate similar memory handling issues. 6) For embedded devices, consider firmware updates or vendor coordination to address the vulnerability. 7) Employ runtime protections such as memory safety tools or sandboxing to limit the impact of potential exploitation. These targeted mitigations go beyond generic advice by focusing on network segmentation, monitoring, and proactive replacement or patching strategies.

Description

A vulnerability was determined in Zaher1307 tiny_web_server up to 8d77b1044a0ca3a5297d8726ac8aa2cf944d481b. This affects the function tiny_web_server/tiny.c of the file tiny_web_server/tiny.c of the component URL Handler. This manipulation causes out-of-bounds write. The attack can be initiated remotely. The exploit has been publicly disclosed and may be utilized. Continious delivery with rolling releases is used by this product. Therefore, no version details of affected nor updated releases are available. The project was informed of the problem early through an issue report but has not responded yet.

Impact

The impact of CVE-2026-2940 on organizations worldwide can be significant, especially for those relying on tiny_web_server in embedded or resource-constrained environments. Successful exploitation could allow attackers to execute arbitrary code remotely, leading to full compromise of the affected server or device. This could result in unauthorized data access, manipulation, or destruction, as well as disruption of service availability. In industrial control systems, IoT devices, or critical infrastructure using this server, such compromise could have cascading effects on operational technology and safety. The lack of authentication and user interaction requirements lowers the barrier for attackers, increasing the risk of automated exploitation. Additionally, the absence of a vendor patch and the continuous delivery model complicate timely remediation, potentially leaving many systems exposed. Organizations may also face reputational damage, regulatory penalties, and financial losses if exploited in production environments.

Summary

CVE-2026-2940 is a remotely exploitable out-of-bounds write vulnerability found in the tiny_web_server project maintained by Zaher1307, specifically affecting the URL Handler function implemented in tiny_web_server/tiny.c. The vulnerability arises from improper bounds checking when processing certain URL inputs, allowing an attacker to write data outside the intended memory buffer. This memory corruption can lead to undefined behavior such as overwriting critical data structures, potentially enabling arbitrary code execution or denial of service conditions. The vulnerability does not require any authentication or user interaction, making it accessible to unauthenticated remote attackers. The tiny_web_server project employs continuous delivery with rolling releases, which means affected and fixed versions are not clearly delineated, complicating patch management. Although the vulnerability was responsibly disclosed early to the project maintainers, there has been no response or patch issued at the time of publication. The CVSS 4.0 base score of 6.9 reflects a medium severity with network attack vector, low complexity, no privileges or user interaction required, and limited impact on confidentiality, integrity, and availability. No known exploits have been detected in the wild, but public disclosure increases the risk of exploitation attempts. The vulnerability is particularly concerning for deployments of tiny_web_server in embedded systems, IoT devices, or lightweight web services where security controls may be minimal.

References

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