{"id":"CVE-2026-125233","kind":"vulnerability","aliases":["CVE-2026-125233"],"related":[],"title":"FFmpeg: crafted subtitles overflow heap during DVB subtitle encoding","description":"FFmpeg through 9.0.2 contains a heap buffer overflow vulnerability in dvbsub_encode() in libavcodec/dvbsubenc.c that undercounts each CLUT segment header by two bytes. Attackers can supply a file with many bitmap subtitle rectangles that, when transcoded to the dvbsub encoder, writes past the output buffer and corrupts heap memory.","summary":"FFmpeg's DVB subtitle encoder miscounts CLUT segment header size by two bytes, so a crafted file with many bitmap subtitle rectangles writes past its output buffer. An attacker who gets a file transcoded can corrupt heap memory, which may allow code execution.","severity":"high","cvss":8.5,"epss":null,"exploited":false,"exploited_at":null,"products":[],"ecosystems":[],"tags":["ffmpeg","libavcodec","media-processing","package"],"not_affected_if":["no-dvbsub-encoding","trusted-input-only"],"how_to_check":"- Run `ffmpeg -version` and compare against the fixed release in the product ranges (unknown in the sources).\n- Check whether your pipelines transcode DVB subtitles with the dvbsub encoder (unknown in the sources).","fix":"- Move to a patched FFmpeg build; the fixed version is not stated in the sources. See the linked patch on github.com.","status":"open","published_at":"2026-11-09T19:17:01+00:00","first_seen_at":"2026-11-09T19:28:20+00:00","triaged_at":"2026-11-09T19:29:29+00:00","updated_at":"2026-11-09T19:29:29+00:00","category":"package","confidence":0.6,"triage":{"at":"2026-11-09T19:29:29Z","model":"claude-haiku-5-5","output":{"fix":"- Move to a patched FFmpeg build; the fixed version is not stated in the sources. See the linked patch on github.com.","reach":"internet","title":"FFmpeg: crafted subtitles overflow heap during DVB subtitle encoding","impact":"high","summary":"FFmpeg's DVB subtitle encoder miscounts CLUT segment header size by two bytes, so a crafted file with many bitmap subtitle rectangles writes past its output buffer. An attacker who gets a file transcoded can corrupt heap memory, which may allow code execution.","audience":"businesses","category":"package","nicknames":[],"who_cares":["ffmpeg","media-processing","libavcodec"],"confidence":0.6,"fix_status":"available","needs_auth":"no","worst_case":"Heap corruption while transcoding a crafted file, possibly code execution","analyst_note":"Confirm the first fixed FFmpeg version from the linked patch on github.com and the vulncheck advisory.","how_to_check":"- Run `ffmpeg -version` and compare against the fixed release in the product ranges (unknown in the sources).\n- Check whether your pipelines transcode DVB subtitles with the dvbsub encoder (unknown in the sources).","plain_action":"","product_name":"","needs_analyst":true,"not_affected_if":["no-dvbsub-encoding","trusted-input-only"],"who_is_affected":"Systems that run FFmpeg to transcode video with DVB subtitle output, especially on untrusted uploaded media. Pipelines that never encode DVB subtitles or only process trusted files are less exposed. The sources do not list affected product ranges beyond 'through 9.0.2'.","user_interaction":"no","product_ecosystem":"","needs_special_setup":"yes","severity_if_unknown":"high"},"cost_usd":0.000779,"input_tokens":4641,"output_tokens":629,"severity_before":"high"},"analyst_status":null,"analyst_note":null,"search":"'-125233':12A,15A '-2026':11A,14A '9.0.2':67C 'allow':62B 'attack':50B,88C 'bitmap':41B,95C 'buffer':48B,71C,109C 'byte':34B,87C 'clut':28B,82C 'code':63B 'contain':68C 'corrupt':57B,111C 'craft':2A,37B 'cve':10A,13A 'dvb':7A,24B 'dvbsub':75C,103C 'encod':9A,26B,76C,104C 'execut':64B 'ffmpeg':1A,16B,22B,65C 'file':38B,54B,92C 'get':52B 'header':30B,84C 'heap':5A,58B,70C,112C 'libavcodec':17B 'libavcodec/dvbsubenc.c':78C 'mani':40B,94C 'may':61B 'media':19B 'media-process':18B 'memori':59B,113C 'miscount':27B 'output':47B,108C 'overflow':4A,72C 'packag':21B 'past':45B,106C 'process':20B 'rectangl':43B,97C 'segment':29B,83C 'size':31B 'subtitl':3A,8A,25B,42B,96C 'suppli':90C 'transcod':55B,100C 'two':33B,86C 'undercount':80C 'vulner':73C 'write':44B,105C","nicknames":[],"mitigations":[],"who_affected":"Systems that run FFmpeg to transcode video with DVB subtitle output, especially on untrusted uploaded media. Pipelines that never encode DVB subtitles or only process trusted files are less exposed. The sources do not list affected product ranges beyond 'through 9.0.2'.","tier":"B","verified":{},"analyst_revisit_at":null,"fix_status":"available","audience":"businesses","plain_action":null,"pkeys":[],"ptokens":[],"labels":["ffmpeg","high","libavcodec","mediaprocessing","package"],"campaign_type":null,"search_a":"'-125233':12A,15A '-2026':11A,14A 'craft':2A 'cve':10A,13A 'dvb':7A 'encod':9A 'ffmpeg':1A 'heap':5A 'overflow':4A 'subtitl':3A,8A","search_b":"'allow':62B 'attack':50B 'bitmap':41B 'buffer':48B 'byte':34B 'clut':28B 'code':63B 'corrupt':57B 'craft':37B 'dvb':24B 'encod':26B 'execut':64B 'ffmpeg':16B,22B 'file':38B,54B 'get':52B 'header':30B 'heap':58B 'libavcodec':17B 'mani':40B 'may':61B 'media':19B 'media-process':18B 'memori':59B 'miscount':27B 'output':47B 'packag':21B 'past':45B 'process':20B 'rectangl':43B 'segment':29B 'size':31B 'subtitl':25B,42B 'transcod':55B 'two':33B 'write':44B","search_c":"'9.0.2':67C 'attack':88C 'bitmap':95C 'buffer':71C,109C 'byte':87C 'clut':82C 'contain':68C 'corrupt':111C 'dvbsub':75C,103C 'encod':76C,104C 'ffmpeg':65C 'file':92C 'header':84C 'heap':70C,112C 'libavcodec/dvbsubenc.c':78C 'mani':94C 'memori':113C 'output':108C 'overflow':72C 'past':106C 'rectangl':97C 'segment':83C 'subtitl':96C 'suppli':90C 'transcod':100C 'two':86C 'undercount':80C 'vulner':73C 'write':105C","cause_entry":null,"cause_path":null,"disclosures_checked_at":null,"first_public_at":"2026-11-09T19:17:01+00:00","kev":null,"cvss_vector":"CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:P/VC:H/VI:H/VA:H/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-2026-125233","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-125233","severity":null,"published_at":"2026-11-09T19:17:01+00:00","modified_at":"2026-11-09T19:17:01+00:00","first_seen_at":"2026-11-09T19:28:20+00:00","fetched_at":"2026-11-09T19:28:20+00:00","note":null}],"documents":[{"id":109357,"url":"https://github.com/FFmpeg/FFmpeg/commit/7f80b2ad83f37a4998d9617495c92b28a7339a90","title":"Patch: github.com","kind":"other","source":"nvd","publisher":"vendor","text":null,"published_at":null,"relation":"fix","confidence":null,"note":"Patch: github.com"},{"id":109358,"url":"https://www.vulncheck.com/advisories/ffmpeg-through-9.0.2-heap-buffer-overflow-via-dvb-subtitle-encoder","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"}