# CVE-2026-21089: Samsung libsubextractor out-of-bounds write in style tag parsing

Source: https://junglewise.ai/threats/cve-2026-21089-samsung-libsubextractor-out-of-bounds-write-in-style-tag-parsing  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-09-09. Updated: 2026-09-26  
License: CC BY 4.0 with a link back

CVE-2026-21089 · Severity: high · CVSS 7.8 · Published 2026-09-09

A library used by Samsung devices to extract and parse subtitle content contains a flaw in how it validates input when removing style tags. A local attacker could exploit this to write data outside the intended memory boundaries, potentially crashing the application or executing arbitrary code with the privileges of the process handling the subtitle data.

Technologies: [Samsung One UI](https://junglewise.ai/threats/technologies/one-ui). Vendors: [Samsung](https://junglewise.ai/threats/vendors/samsung).

## Quick answers

**Is CVE-2026-21089 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-21089 being exploited in the wild.

**How severe is CVE-2026-21089?** High severity, with a CVSS score of 7.8, published 9 September 2026.

**Which products and versions are affected?** Samsung One UI prior to SMR Sep-2026 Release 1.

**Is there a fix for CVE-2026-21089?** A patch was published on 2026-09: SMR Sep-2026 Release 1 Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-21089 attacked?** It is attacked with local access, in device firmware.

**Am I affected by CVE-2026-21089?** Check whether you run Samsung One UI 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

The vulnerability is an out-of-bounds write (improper input validation / buffer overflow) in libsubextractor.so, a Samsung library responsible for subtitle extraction and formatting. The flaw occurs in the style tag removal logic when processing malformed or specially crafted subtitle input. An attacker with local access can provide a crafted subtitle file to trigger the out-of-bounds write, enabling memory corruption that could lead to denial of service or code execution. The vulnerability affects versions prior to the September 2026 SMR (Security Maintenance Release) 1 patch. No active exploitation in the wild is currently documented.

## Affected products

- Samsung One UI prior to SMR Sep-2026 Release 1

## Timeline

- 2026-09-09: disclosed
- 2026-09: patched: SMR Sep-2026 Release 1

## References

- [https://security.samsungmobile.com/securityUpdate.smsb?year=2026&month=09](https://security.samsungmobile.com/securityUpdate.smsb?year=2026&month=09)

## Related threats

- [Samsung framework services missing permission checks](https://junglewise.ai/threats/cve-2026-69002-incorrect-authorization-in-samsung-framework-services-due-to)
- [Samsung One UI out-of-bounds write in libsthmbc.so](https://junglewise.ai/threats/cve-2026-21111-samsung-one-ui-out-of-bounds-write-in-libsthmbc-so)
- [Samsung One UI out-of-bounds write in libsavscmn.so](https://junglewise.ai/threats/cve-2026-21110-samsung-one-ui-out-of-bounds-write-in-libsavscmn-so)