Buffer overflow in L-Smash
CVE-2026-120456
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.
Vulnerability class: Buffer Overflow
Published · last modified .
CVSS v3 metric
CVSS v3 base score 6.1 (Medium). Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:H.
EPSS exploit prediction
No EPSS score from FIRST.org yet. New CVEs usually get one within a few days; no score means no signal yet, not low risk. How EPSS works.
Affected products
Weakness classification (CWE)
References
- github.com/l-smash/l-smash/issues/112 (issue-tracking)
- github.com/l-smash/l-smash/commit/805ee3c9632e054198d3cb5b09c7b7aa36cdd791 (patch)
- github.com/l-smash/l-smash/blob/v2.14.5/core/read.c (technical-description)
- github.com/l-smash/l-smash/blob/v2.14.5/core/read.c (technical-description)
- hackmd.io/@haindpwn/lsmash-hdlr-dref-box-size-oob-write (technical-description)
- www.vulncheck.com/advisories/l-smash-through-2.14.5-heap-out-of-bounds-write-vi… (third-party-advisory)
Frequently asked questions
- What is CVE-2026-120456?
- CVE-2026-120456 is a medium-severity vulnerability in L-Smash, classified under Out-of-bounds Write. CVSS score: 6.1/10. Published 2026-11-02.
- How severe is CVE-2026-120456?
- Medium severity. CVSS v3 base score is 6.1 out of 10.