# CVE-2026-51263: schreibfaul1 ESP32-audioI2S heap buffer overflow in speech functions

Source: https://junglewise.ai/threats/cve-2026-51263-schreibfaul1-esp32-audioi2s-heap-buffer-overflow-in-speech  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-07-28. Updated: 2026-07-28  
License: CC BY 4.0 with a link back

CVE-2026-51263 · Severity: info · CVSS 0 · Published 2026-07-28

A vulnerability exists in the ESP32-audioI2S library, which is used by ESP32 microcontrollers to handle audio playback and text-to-speech functions. An attacker can send a specially crafted, oversized text request to the device, causing it to crash or potentially allowing the attacker to take control of the device. This could lead to a permanent disruption of audio services or unauthorized access to the device's operations.

Technologies: [Schreibfaul1 ESP32-audioI2S](https://junglewise.ai/threats/technologies/esp32-audioi2s). Vendors: [Schreibfaul1](https://junglewise.ai/threats/vendors/schreibfaul1).

## Quick answers

**Is CVE-2026-51263 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-51263 being exploited in the wild.

**How severe is CVE-2026-51263?** Informational severity, with a CVSS score of 0, published 28 July 2026.

**Which products and versions are affected?** Schreibfaul1 ESP32-audioI2S 3.4.5.

**Is there a fix for CVE-2026-51263?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2026-51263 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-51263?** Check whether you run Schreibfaul1 ESP32-audioI2S at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

A heap-based buffer overflow exists in the `Audio::openai_speech` and `connecttospeech()` functions within `src/Audio.cpp`. The vulnerability stems from the manual construction of JSON request bodies and HTTP headers by concatenating externally controllable strings without enforcing length restrictions or boundary validation. Specifically, the library performs URL encoding on user-supplied speech text—which expands the string length—and appends the result to a fixed-size `ps_ptr` heap buffer. An unauthenticated remote attacker can provide an oversized speech string to trigger an out-of-bounds write, leading to memory corruption, denial of service (watchdog reboot), or potential arbitrary code execution. As of the advisory date, a vendor patch is reportedly under development.

## Affected products

- schreibfaul1 ESP32-audioI2S 3.4.5

## Timeline

- 2026-07-28: disclosed: CVE published to NVD

## References

- [https://github.com/programmervuln/cveadvisory-/blob/main/CVE-2026-51263](https://github.com/programmervuln/cveadvisory-/blob/main/CVE-2026-51263)
- [https://github.com/schreibfaul1/ESP32-audioI2S/blob/master/src/Audio.cpp](https://github.com/schreibfaul1/ESP32-audioI2S/blob/master/src/Audio.cpp)

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