arendst Tasmota up to 15.3.0.3 fetch_jpg uint16_t heap-based overflow

Summaryinfo

A vulnerability was found in arendst Tasmota up to 15.3.0.3. It has been classified as critical. The impacted element is the function fetch_jpg. This manipulation of the argument uint16_t causes heap-based overflow. This vulnerability is registered as CVE-2026-38427. Remote exploitation of the attack is possible. No exploit is available.

Detailsinfo

A vulnerability classified as critical was found in arendst Tasmota up to 15.3.0.3. Affected by this vulnerability is the function fetch_jpg. The manipulation of the argument uint16_t with an unknown input leads to a heap-based overflow vulnerability. The CWE definition for the vulnerability is CWE-122. A heap overflow condition is a buffer overflow, where the buffer that can be overwritten is allocated in the heap portion of memory, generally meaning that the buffer was allocated using a routine such as malloc(). As an impact it is known to affect confidentiality, integrity, and availability. The summary by CVE is:

An issue in fetch_jpg() in xdrv_10_scripter.ino in Tasmota through 15.3.0.3 allows a remote attacker to cause heap buffer overflow. The Content-Length from a JPEG stream is stored in a uint16_t variable; values above 65535 wrap around, causing allocation of a smaller buffer than the data actually read.

It is possible to read the advisory at github.com. This vulnerability is known as CVE-2026-38427 since 04/06/2026. The exploitation appears to be easy. The attack can be launched remotely. Technical details of the vulnerability are known, but there is no available exploit. The pricing for an exploit might be around USD $0-$5k at the moment (estimation calculated on 05/27/2026).

There is no information about possible countermeasures known. It may be suggested to replace the affected object with an alternative product.

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Productinfo

Vendor

• arendst

Name

• Tasmota

Version

• 15.3.0.0
• 15.3.0.1
• 15.3.0.2
• 15.3.0.3

Website

• Product: https://github.com/arendst/Tasmota/

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Submitinfo

Duplicate

• Submit #XXXXXX: Xxxxxxx Xxxxxxx Xx.x.x.x Xxxxxx Xxxxxxxxxx (by sermikro)

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