Two VLC Media Player Flaws Let Crafted PNGs Corrupt Heap Memory and Hostile RealRTSP Servers Leak Sensitive Data

VLC media player contains an integer overflow (CWE-190) in its picture buffer allocation: in AllocatePicture (src/misc/picture.c) the byte total is accumulated with 32-bit arithmetic, so for very large picture dimensions the product of plane pitch and lines wraps before it is widened to a 64-bit size, and both existing guard checks evaluate only the already-wrapped value. As a result, aligned_alloc reserves a much smaller buffer than the picture actually requires, and a crafted PNG whose IHDR chunk declares very large width and height values - which reaches the code through the image demuxer that only limits the input file's byte count, not the declared dimensions - causes the PNG decoder (modules/codec/png.c) to write past the end of the allocation with attacker-influenced length and content (CWE-787). Opening the malicious PNG file directly or through a playlist entry is sufficient to trigger the flaw under default settings, and per the high CVSS 4.0 score (8.6) the attacker gains high confidentiality, integrity, and availability impact on the player process, i.e., controlled heap corruption that can crash VLC and potentially execute code. All VLC users who open untrusted image files are potentially affected; the available data does not specify affected version ranges. No public proof-of-concept is known and the flaw is not listed in CISA's KEV, so no exploitation has been reported to date.

Do: Until a patched VLC release is available, avoid opening untrusted PNG image files or playlist entries referencing images with VLC, and consider setting a different application as the default PNG handler. No fixed version is specified in the available data, so monitor VideoLAN advisories for an update addressing CVE-2026-56711 and apply it promptly when released.

VLC media player's RTSP access module contains an out-of-bounds read caused by improper null-termination: RtspReadLine uses strncpy with the full buffer length (writing no terminator when the response line is as long as the destination), and rtsp_get then passes the 4096-byte BUF_SIZE buffer to strdup, which reads past the end of the heap allocation whenever a server returns a line of 4096 bytes or more. The flaw is triggered simply by opening a playlist entry that names a realrtsp URL, and the attacker controls the line length and therefore how far the over-read runs. Because the affected line is the Session header, the disclosed bytes are retained as the session identifier and sent back to the server on every subsequent request, so the operator of a hostile server directly receives adjacent client heap memory (high confidentiality impact with no integrity or availability impact, per the CVSS 4.0 score of 6.9). Anyone using a VLC build with the RTSP module enabled is affected — the official VideoLAN builds enable it, while some distribution packages ship it disabled — and user interaction is required. No public proof-of-concept or confirmed in-the-wild exploitation is known; EPSS assigns a 0.3% probability of exploitation within 30 days and the flaw is not in CISA's KEV.

Do: Verify whether your VLC build includes the RTSP access module (official VideoLAN builds do; some Linux distributions ship it disabled). Until a patched release is identified — the disclosure data does not list a fixed version — avoid opening playlists or stream links pointing to realrtsp/RTSP URLs from untrusted servers, or disable the RTSP access module. Monitor VideoLAN for an updated release addressing CVE-2026-73324.