{"id":"CVE-2026-121623","kind":"vulnerability","aliases":["CVE-2026-121623"],"related":[],"title":"Symfony Serializer: uppercase data: scheme lets requests read local files","description":"The Symfony Serializer component DataUriNormalizer::denormalize() matches the data: scheme with a case-sensitive regular expression, allowing a value with an uppercase scheme, such as DATA:,/../../../etc/passwd, to bypass it, resulting in Arbitrary Local File Read through Path Traversal in Symfony versions prior to 5.4.56, 6.x prior to 6.4.50, 7.x prior to 7.4.23, and 8.x prior to 8.1.11.\n\nA value whose scheme is not lowercase data: are treated as a local file path and opened instead of being decoded as inline data, so the resulting File, \\SplFileInfo, or \\SplFileObject points at a file on the server, which the application then handles as the uploaded content.\n\nAny endpoint that deserializes untrusted input into one of these types is affected. FrameworkBundle registers DataUriNormalizer ahead of ObjectNormalizer by default. A single request with a crafted DATA: value is enough to read arbitrary local files that the application can access, with no authentication needed if the endpoint is public.","summary":"The Symfony Serializer's DataUriNormalizer checks for the data: scheme case-sensitively, so a value like DATA:,/../../../etc/passwd is treated as a file path instead of inline data. An attacker who can reach a deserializing endpoint can read arbitrary local files the application can access.","severity":"high","cvss":8.2,"epss":null,"exploited":false,"exploited_at":null,"products":[],"ecosystems":[],"tags":["package","php","symfony","symfony-serializer"],"not_affected_if":["no-file-type-denormalization","no-untrusted-deserialization"],"how_to_check":"- Check the installed version with `composer show symfony/serializer` and compare it to the fixed ranges below.\n- Look for endpoints that deserialize untrusted input into File, SplFileInfo or SplFileObject types.","fix":"- Upgrade symfony/serializer to `5.4.56`, `6.4.50`, `7.4.23` or `8.1.11` depending on the major line in use.","status":"open","published_at":"2026-11-06T16:17:52+00:00","first_seen_at":"2026-11-06T16:42:41+00:00","triaged_at":"2026-11-06T16:44:35+00:00","updated_at":"2026-11-06T16:44:35+00:00","category":"package","confidence":0.8,"triage":{"at":"2026-11-06T16:44:35Z","model":"claude-haiku-5-5","output":{"fix":"- Upgrade symfony/serializer to `5.4.56`, `6.4.50`, `7.4.23` or `8.1.11` depending on the major line in use.","reach":"internet","title":"Symfony Serializer: uppercase data: scheme lets requests read local files","impact":"high","summary":"The Symfony Serializer's DataUriNormalizer checks for the data: scheme case-sensitively, so a value like DATA:,/../../../etc/passwd is treated as a file path instead of inline data. An attacker who can reach a deserializing endpoint can read arbitrary local files the application can access.","audience":"developers","category":"package","nicknames":[],"who_cares":["symfony","php","symfony-serializer"],"confidence":0.8,"fix_status":"available","needs_auth":"no","worst_case":"Arbitrary local files readable by the application process.","analyst_note":"","how_to_check":"- Check the installed version with `composer show symfony/serializer` and compare it to the fixed ranges below.\n- Look for endpoints that deserialize untrusted input into File, SplFileInfo or SplFileObject types.","plain_action":"","needs_analyst":false,"not_affected_if":["no-untrusted-deserialization","no-file-type-denormalization"],"who_is_affected":"Applications that use the Symfony Serializer to deserialize untrusted input into File, SplFileInfo or SplFileObject. FrameworkBundle registers DataUriNormalizer ahead of ObjectNormalizer by default, so default Symfony apps that accept such input are exposed. Public endpoints need no authentication.","user_interaction":"no","needs_special_setup":"no","severity_if_unknown":"high"},"cost_usd":0.000745,"input_tokens":4517,"output_tokens":586,"severity_before":"high"},"analyst_status":null,"analyst_note":null,"search":"'-121623':13A,16A '-2026':12A,15A '/../../../etc/passwd':41B,96C '5.4.56':114C '6':115C '6.4.50':119C '7':120C '7.4.23':124C '8':126C '8.1.11':130C 'access':68B,218C 'affect':190C 'ahead':194C 'allow':86C 'applic':66B,171C,216C 'arbitrari':62B,102C,211C 'attack':53B 'authent':221C 'bypass':98C 'case':34B,82C 'case-sensit':33B,81C 'check':28B 'compon':72C 'content':177C 'craft':204C 'cve':11A,14A 'data':4A,31B,40B,51B,77C,95C,138C,154C,205C 'dataurinorm':27B,73C,193C 'decod':151C 'default':198C 'denorm':74C 'deseri':58B,181C 'endpoint':59B,179C,225C 'enough':208C 'express':85C 'file':10A,46B,64B,104C,144C,158C,165C,213C 'frameworkbundl':191C 'handl':173C 'inlin':50B,153C 'input':183C 'instead':48B,148C 'let':6A 'like':39B 'local':9A,63B,103C,143C,212C 'lowercas':137C 'match':75C 'need':222C 'objectnorm':196C 'one':185C 'open':147C 'packag':17B 'path':47B,107C,145C 'php':18B 'point':162C 'prior':112C,117C,122C,128C 'public':227C 'reach':56B 'read':8A,61B,105C,210C 'regist':192C 'regular':84C 'request':7A,201C 'result':100C,157C 'scheme':5A,32B,78C,92C,134C 'sensit':35B,83C 'serial':2A,22B,25B,71C 'server':168C 'singl':200C 'splfileinfo':159C 'splfileobject':161C 'symfoni':1A,19B,21B,24B,70C,110C 'symfony-seri':20B 'travers':108C 'treat':43B,140C 'type':188C 'untrust':182C 'upload':176C 'uppercas':3A,91C 'valu':38B,88C,132C,206C 'version':111C 'whose':133C 'x':116C,121C,127C","nicknames":[],"mitigations":[],"who_affected":"Applications that use the Symfony Serializer to deserialize untrusted input into File, SplFileInfo or SplFileObject. FrameworkBundle registers DataUriNormalizer ahead of ObjectNormalizer by default, so default Symfony apps that accept such input are exposed. Public endpoints need no authentication.","tier":"B","verified":{},"analyst_revisit_at":null,"fix_status":"available","audience":"developers","plain_action":null,"pkeys":[],"ptokens":[],"labels":["high","package","php","symfony","symfonyserializer"],"campaign_type":null,"search_a":"'-121623':13A,16A '-2026':12A,15A 'cve':11A,14A 'data':4A 'file':10A 'let':6A 'local':9A 'read':8A 'request':7A 'scheme':5A 'serial':2A 'symfoni':1A 'uppercas':3A","search_b":"'/../../../etc/passwd':41B 'access':68B 'applic':66B 'arbitrari':62B 'attack':53B 'case':34B 'case-sensit':33B 'check':28B 'data':31B,40B,51B 'dataurinorm':27B 'deseri':58B 'endpoint':59B 'file':46B,64B 'inlin':50B 'instead':48B 'like':39B 'local':63B 'packag':17B 'path':47B 'php':18B 'reach':56B 'read':61B 'scheme':32B 'sensit':35B 'serial':22B,25B 'symfoni':19B,21B,24B 'symfony-seri':20B 'treat':43B 'valu':38B","search_c":"'/../../../etc/passwd':96C '5.4.56':114C '6':115C '6.4.50':119C '7':120C '7.4.23':124C '8':126C '8.1.11':130C 'access':218C 'affect':190C 'ahead':194C 'allow':86C 'applic':171C,216C 'arbitrari':102C,211C 'authent':221C 'bypass':98C 'case':82C 'case-sensit':81C 'compon':72C 'content':177C 'craft':204C 'data':77C,95C,138C,154C,205C 'dataurinorm':73C,193C 'decod':151C 'default':198C 'denorm':74C 'deseri':181C 'endpoint':179C,225C 'enough':208C 'express':85C 'file':104C,144C,158C,165C,213C 'frameworkbundl':191C 'handl':173C 'inlin':153C 'input':183C 'instead':148C 'local':103C,143C,212C 'lowercas':137C 'match':75C 'need':222C 'objectnorm':196C 'one':185C 'open':147C 'path':107C,145C 'point':162C 'prior':112C,117C,122C,128C 'public':227C 'read':105C,210C 'regist':192C 'regular':84C 'request':201C 'result':100C,157C 'scheme':78C,92C,134C 'sensit':83C 'serial':71C 'server':168C 'singl':200C 'splfileinfo':159C 'splfileobject':161C 'symfoni':70C,110C 'travers':108C 'treat':140C 'type':188C 'untrust':182C 'upload':176C 'uppercas':91C 'valu':88C,132C,206C 'version':111C 'whose':133C 'x':116C,121C,127C","first_public_at":"2026-11-04T11:43:37+00:00","kev":null,"cvss_vector":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/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":"596c5446-0ce5-4ba2-aa66-48b3b757a647","poc_count":0,"sources":[{"source":"nvd","external_id":"CVE-2026-121623","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-121623","severity":null,"published_at":"2026-11-06T16:17:52+00:00","modified_at":"2026-11-06T16:17:52+00:00","first_seen_at":"2026-11-06T16:42:41+00:00","fetched_at":"2026-11-06T16:42:41+00:00","note":null}],"documents":[{"id":87931,"url":"https://github.com/symfony/symfony/commit/a0c551861ac23f888dfe6d1157ca78f4e220f3b7","title":"Patch: github.com","kind":"other","source":"nvd","publisher":"vendor","text":null,"published_at":null,"relation":"fix","confidence":null,"note":"Patch: github.com"},{"id":87932,"url":"https://github.com/symfony/symfony/security/advisories/GHSA-pxj9-jh84-vhm5","title":"Vendor advisory: github.com","kind":"vendor","source":"nvd","publisher":"vendor","text":null,"published_at":"2026-11-04T11:43:37+00:00","relation":"advisory","confidence":null,"note":"Vendor advisory: github.com"}],"exploit_sources":[],"notice":"Free to read, with fair use of about 60 pages a minute. For higher limits or API access: sales@infrastack.ai"}