# CVE-2026-120456: L-SMASH through 2.14.5 Heap Out-of-Bounds Write via hdlr and url Boxes

Status: published. Published: 2026-11-02. Updated: 2026-11-02.

L-SMASH through 2.14.5 contains a heap out-of-bounds write vulnerability in isom_read_hdlr() and isom_read_dref_entry() in core/read.c triggered by oversized box sizes. Attackers can supply crafted MP4 or MOV files declaring hdlr or url box sizes larger than remaining data, stalling the stream position and corrupting heap memory to crash applications.

## Remediation

No remediation reported in collected sources

## Affected products and versions

- L-SMASH / L-SMASH: ≥ 0; ≤ 2.14.5 (affected, semver). Source: CNA: VulnCheck

## Severity and prioritization

- CVSS 4.0: 6.9 (medium); CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:P/VC:N/VI:L/VA:H/SC:N/SI:N/SA:N; source: CNA: VulnCheck

- CVSS 3.1: 6.1 (medium); CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:H; source: CNA: VulnCheck

- CISA KEV: No listing in collected sources

- EPSS: Not available

- SSVC: Not available

- Weaknesses: CWE-787

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://github.com/l-smash/l-smash/issues/112 (CNA: VulnCheck; issue-tracking)

- https://github.com/l-smash/l-smash/commit/805ee3c9632e054198d3cb5b09c7b7aa36cdd791 (CNA: VulnCheck; patch)

- https://github.com/l-smash/l-smash/blob/v2.14.5/core/read.c#L688-L717 (CNA: VulnCheck; technical-description)

- https://github.com/l-smash/l-smash/blob/v2.14.5/core/read.c#L853-L876 (CNA: VulnCheck; technical-description)

- https://hackmd.io/@haindpwn/lsmash-hdlr-dref-box-size-oob-write (CNA: VulnCheck; technical-description)

- https://www.vulncheck.com/advisories/l-smash-through-2.14.5-heap-out-of-bounds-write-via-hdlr-and-url-boxes (CNA: VulnCheck; third-party-advisory)

## Provenance

- CNA: VulnCheck: https://www.cve.org/CVERecord?id=CVE-2026-120456; retrieved 2026-11-02; source updated 2026-11-02

Revision: 858645b0d9bf57850adbcd243e762714b8438f8de1b4799c5f8526fc0f3a9210

Canonical: https://y2.dev/cve/CVE-2026-120456

## Agent and API access

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- Public catalog: https://y2.dev/cve/index.json. Follow nextCursor with the same search and limit (1–100). A null cursor marks the end.

- WebMCP: search_cve_disclosures, get_cve_disclosure, get_cve_page_markdown, get_y2_cve_access. Available in compatible browsers.

- Cyber API: https://api.y2.dev/api/v2/cyber/cves and https://api.y2.dev/api/v2/cyber/cves/{cveId}.

- Y2 Pro or Elite: create a workspace API key with the intel:cyber scope and send Authorization: Bearer <Y2_API_KEY>. Setup: https://y2.dev/docs/api/create-key.

- x402: Pay per request without an account or API key. Omit Authorization, read the HTTP 402 PAYMENT-REQUIRED challenge, validate its current requirements, and retry with PAYMENT-SIGNATURE through an authorized payment client. These browser tools never make payments. Guide: https://y2.dev/docs/api/x402.

- OpenAPI: https://y2.dev/api/openapi.yaml. Agent access metadata: https://y2.dev/cve/agent.json.

Collected public records only. Check source status for coverage and freshness.