# CVE-2026-34961: barebox out-of-bounds read in ext4 extent parsing

Source: https://junglewise.ai/threats/cve-2026-34961-barebox-out-of-bounds-read-in-ext4-extent-parsing  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-05-11. Updated: 2026-07-18  
License: CC BY 4.0 with a link back

CVE-2026-34961 · Severity: medium · CVSS 6.2 · Published 2026-05-11

barebox is an open-source bootloader used to initialize hardware and start the operating system on embedded devices like industrial controllers and automotive systems. A vulnerability in how it handles ext4 filesystems could allow an attacker with physical access to the device (via USB or SD card) or control over the local boot network to crash the system during startup. This could lead to a denial-of-service state where the device fails to boot correctly, potentially impacting operations or requiring manual recovery.

Technologies: [Barebox](https://junglewise.ai/threats/technologies/barebox). Vendors: [Barebox](https://junglewise.ai/threats/vendors/barebox).

## Quick answers

**Is CVE-2026-34961 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-34961 being exploited in the wild.

**How severe is CVE-2026-34961?** Medium severity, with a CVSS score of 6.2, published 11 May 2026.

**Which products and versions are affected?** Barebox before 2026.04.0.

**Is there a fix for CVE-2026-34961?** A patch was published on 2026-04-17: Version 2026.04.0 released with fixes for ext4 parsing. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-34961 attacked?** It is attacked with local access or with physical access or from the adjacent network, in device firmware.

**Am I affected by CVE-2026-34961?** Check whether you run Barebox 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

An out-of-bounds read vulnerability (CWE-125) exists in the barebox bootloader's ext4 filesystem implementation. The flaw is located in 'fs/ext4/ext4_common.c' where the 'eh_entries' field, which specifies the number of entries in an extent header, is used as a loop bound without being validated against the actual buffer capacity. An attacker can exploit this by providing a specially crafted ext4 filesystem image via physical media (USB/SD card) or network boot (PXE). During boot-time parsing, the lack of bounds checking causes the pointer to advance beyond the allocated heap buffer, leading to information leaks or a system crash (Denial of Service). The issue is resolved in version 2026.04.0.

## Affected products

- Pengutronix barebox versions prior to 2026.04.0

## Timeline

- 2026-04-17: patched: Version 2026.04.0 released with fixes for ext4 parsing.
- 2026-05-11: disclosed: Initial CVE publication.

## References

- [https://github.com/barebox/barebox](https://github.com/barebox/barebox)
- [https://github.com/barebox/barebox/releases/tag/v2026.04.0](https://github.com/barebox/barebox/releases/tag/v2026.04.0)
- [https://www.vulncheck.com/advisories/barebox-ext4-extent-parsing-out-of-bounds-read](https://www.vulncheck.com/advisories/barebox-ext4-extent-parsing-out-of-bounds-read)
- [https://y637f9qq2x.com/posts/barebox-sandbox-vulns/](https://y637f9qq2x.com/posts/barebox-sandbox-vulns/)

## Related threats

- [Das U-Boot and Barebox FIT signature verification bypass](https://junglewise.ai/threats/cve-2026-46728-das-u-boot-and-barebox-fit-signature-verification-bypass)
- [barebox integer overflow and heap overflow in EFI PE loader](https://junglewise.ai/threats/cve-2026-34963-barebox-integer-overflow-and-heap-overflow-in-efi-pe-loader)
- [barebox infinite loop in ext4 directory parsing](https://junglewise.ai/threats/cve-2026-34962-barebox-infinite-loop-in-ext4-directory-parsing)
- [barebox out-of-bounds read in DHCP option parsing](https://junglewise.ai/threats/cve-2026-34960-barebox-out-of-bounds-read-in-dhcp-option-parsing)
- [barebox FIT signature verification bypass](https://junglewise.ai/threats/cve-2026-33243-barebox-fit-signature-verification-bypass)