{"id":"CVE-2026-125176","kind":"vulnerability","aliases":["CVE-2026-125176"],"related":[],"title":"FFmpeg: crafted Flash Screen Video file leaks heap memory into output","description":"FFmpeg through 9.0.2 contains an uninitialized memory read vulnerability in decode_hybrid() in libavcodec/flashsv.c that reads past decompressed data when decoding 15-bit color pixels. Attackers can supply a crafted Flash Screen Video 2 block whose inflated data ends mid-pixel to leak heap memory into decoded output frames.","summary":"FFmpeg through 9.0.2 reads past decompressed data in the flashsv decoder when a Flash Screen Video 2 block ends mid-pixel. An attacker who supplies such a file can leak heap memory into the decoded video frames.","severity":"medium","cvss":4.8,"epss":null,"exploited":false,"exploited_at":null,"products":[],"ecosystems":[],"tags":["ffmpeg","media-processing","runtime","transcoding"],"not_affected_if":["managed-hosting","no-flsv2-input"],"how_to_check":"- Check the installed FFmpeg version with `ffmpeg -version`\n- Look for a build that includes libavcodec/flashsv.c if you compile FFmpeg yourself","fix":"- FFmpeg through `9.0.2` is affected; the sources do not state a fixed version\n- Patch linked from the NVD record (github.com); the sources do not state the version","status":"open","published_at":"2026-11-09T19:16:52+00:00","first_seen_at":"2026-11-09T19:28:16+00:00","triaged_at":"2026-11-09T19:32:23+00:00","updated_at":"2026-11-09T19:32:23+00:00","category":"runtime","confidence":0.6,"triage":{"at":"2026-11-09T19:32:23Z","model":"claude-haiku-5-5","output":{"fix":"- FFmpeg through `9.0.2` is affected; the sources do not state a fixed version\n- Patch linked from the NVD record (github.com); the sources do not state the version","reach":"unknown","title":"FFmpeg: crafted Flash Screen Video file leaks heap memory into output","impact":"low","summary":"FFmpeg through 9.0.2 reads past decompressed data in the flashsv decoder when a Flash Screen Video 2 block ends mid-pixel. An attacker who supplies such a file can leak heap memory into the decoded video frames.","audience":"developers","category":"runtime","nicknames":[],"who_cares":["ffmpeg","media-processing","transcoding"],"confidence":0.6,"fix_status":"unknown","needs_auth":"unknown","worst_case":"heap memory contents leak into decoded output frames","analyst_note":"Confirm the fixed FFmpeg version from the linked GitHub patch and the VulnCheck advisory; sources only give the affected range through 9.0.2.","how_to_check":"- Check the installed FFmpeg version with `ffmpeg -version`\n- Look for a build that includes libavcodec/flashsv.c if you compile FFmpeg yourself\n- unknown whether the sources list affected builds beyond the stated range","plain_action":"","product_name":"","needs_analyst":true,"not_affected_if":["no-flsv2-input","managed-hosting"],"who_is_affected":"Anything that decodes Flash Screen Video 2 content with FFmpeg's flashsv decoder, such as media pipelines that transcode user uploads. Systems that never decode FSV2 input are unlikely to be exposed. The sources do not say more.","user_interaction":"unknown","product_ecosystem":"","needs_special_setup":"unknown","severity_if_unknown":"medium"},"cost_usd":0.000774,"input_tokens":4630,"output_tokens":621,"severity_before":"medium"},"analyst_status":null,"analyst_note":null,"search":"'-125176':14A,17A '-2026':13A,16A '15':83C '2':40B,95C '9.0.2':26B,64C 'attack':47B,87C 'bit':84C 'block':41B,96C 'color':85C 'contain':65C 'craft':2A,91C 'cve':12A,15A 'data':30B,80C,99C 'decod':34B,59B,72C,82C,109C 'decompress':29B,79C 'end':42B,100C 'ffmpeg':1A,18B,24B,62C 'file':6A,52B 'flash':3A,37B,92C 'flashsv':33B 'frame':61B,111C 'heap':8A,55B,106C 'hybrid':73C 'inflat':98C 'leak':7A,54B,105C 'libavcodec/flashsv.c':75C 'media':20B 'media-process':19B 'memori':9A,56B,68C,107C 'mid':44B,102C 'mid-pixel':43B,101C 'output':11A,110C 'past':28B,78C 'pixel':45B,86C,103C 'process':21B 'read':27B,69C,77C 'runtim':22B 'screen':4A,38B,93C 'suppli':49B,89C 'transcod':23B 'uniniti':67C 'video':5A,39B,60B,94C 'vulner':70C 'whose':97C","nicknames":[],"mitigations":[],"who_affected":"Anything that decodes Flash Screen Video 2 content with FFmpeg's flashsv decoder, such as media pipelines that transcode user uploads. Systems that never decode FSV2 input are unlikely to be exposed. The sources do not say more.","tier":"C","verified":{},"analyst_revisit_at":null,"fix_status":"unknown","audience":"developers","plain_action":null,"pkeys":[],"ptokens":[],"labels":["ffmpeg","mediaprocessing","medium","runtime","transcoding"],"campaign_type":null,"search_a":"'-125176':14A,17A '-2026':13A,16A 'craft':2A 'cve':12A,15A 'ffmpeg':1A 'file':6A 'flash':3A 'heap':8A 'leak':7A 'memori':9A 'output':11A 'screen':4A 'video':5A","search_b":"'2':40B '9.0.2':26B 'attack':47B 'block':41B 'data':30B 'decod':34B,59B 'decompress':29B 'end':42B 'ffmpeg':18B,24B 'file':52B 'flash':37B 'flashsv':33B 'frame':61B 'heap':55B 'leak':54B 'media':20B 'media-process':19B 'memori':56B 'mid':44B 'mid-pixel':43B 'past':28B 'pixel':45B 'process':21B 'read':27B 'runtim':22B 'screen':38B 'suppli':49B 'transcod':23B 'video':39B,60B","search_c":"'15':83C '2':95C '9.0.2':64C 'attack':87C 'bit':84C 'block':96C 'color':85C 'contain':65C 'craft':91C 'data':80C,99C 'decod':72C,82C,109C 'decompress':79C 'end':100C 'ffmpeg':62C 'flash':92C 'frame':111C 'heap':106C 'hybrid':73C 'inflat':98C 'leak':105C 'libavcodec/flashsv.c':75C 'memori':68C,107C 'mid':102C 'mid-pixel':101C 'output':110C 'past':78C 'pixel':86C,103C 'read':69C,77C 'screen':93C 'suppli':89C 'uniniti':67C 'video':94C 'vulner':70C 'whose':97C","cause_entry":null,"cause_path":null,"disclosures_checked_at":null,"first_public_at":"2026-11-09T19:16:52+00:00","kev":null,"cvss_vector":"CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:P/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X","cvss_by":"disclosure@vulncheck.com","poc_count":0,"sources":[{"source":"nvd","external_id":"CVE-2026-125176","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-125176","severity":null,"published_at":"2026-11-09T19:16:52+00:00","modified_at":"2026-11-09T19:16:52+00:00","first_seen_at":"2026-11-09T19:28:16+00:00","fetched_at":"2026-11-09T19:28:16+00:00","note":null}],"documents":[{"id":109240,"url":"https://github.com/FFmpeg/FFmpeg/commit/16d0f7f408ba47b4091a22109d4f22f5fd57820a","title":"Patch: github.com","kind":"other","source":"nvd","publisher":"vendor","text":null,"published_at":null,"relation":"fix","confidence":null,"note":"Patch: github.com"},{"id":109241,"url":"https://www.vulncheck.com/advisories/ffmpeg-through-9.0.2-uninitialized-memory-read-in-flash-screen-video-2-decoder","title":"Third-party advisory: www.vulncheck.com","kind":"advisory","source":"nvd","publisher":"research","text":null,"published_at":null,"relation":"advisory","confidence":null,"note":"Third-party advisory: www.vulncheck.com"}],"disclosures":[],"exploit_sources":[],"notice":"Free to read, with fair use of about 60 pages a minute. For higher limits or API access: sales@infrastack.ai"}