Vulnerability · Published Nov 2, 2026 · Assigned by VulnCheck
CVE-2026-120456L-SMASH through 2.14.5 Heap Out-of-Bounds Write via hdlr and url Boxes
Medium 6.1
In plain English
A medium-severity out-of-bounds write in L-SMASH from L-SMASH. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.2% (higher than 5% of all known vulnerabilities).
Severity (CVSS 3.1)6.1Medium
Exploit odds (30 days)0.2%top 95.1% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known
Official description
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.
Affected products (as reported)
Weakness: CWE-787 · Vector: CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:H
References
- https://github.com/l-smash/l-smash/issues/112 issue-tracking
- https://github.com/l-smash/l-smash/commit/805ee3c9632e054198d3cb5b09c7b7aa36cdd791 patch
- https://github.com/l-smash/l-smash/blob/v2.14.5/core/read.c#L688-L717 technical-description
- https://github.com/l-smash/l-smash/blob/v2.14.5/core/read.c#L853-L876 technical-description
- https://hackmd.io/@haindpwn/lsmash-hdlr-dref-box-size-oob-write technical-description
- VulnCheck Advisory: L-SMASH through 2.14.5 Heap Out-of-Bounds Write via hdlr and url Boxes third-party-advisory