{"id":"CVE-2026-91971","kind":"vulnerability","aliases":["CVE-2026-91971","GHSA-4vh2-39rq-rq8j","GO-2026-6717"],"related":[],"title":"Vikunja: Unbounded image decode on avatar and project-background uploads enables decode/resize amplification in code.vikunja.io/api","description":"Vikunja: Unbounded image decode on avatar and project-background uploads enables decode/resize amplification in code.vikunja.io/api.\n\nNOTE: The source advisory for this report contains additional versions that could not be automatically mapped to standard Go module versions.\n\n(If this is causing false-positive reports from vulnerability scanners, please suggest an edit to the report.)\n\nThe additional affected modules and versions are: code.vikunja.io/api before v2.6.0.","summary":"Vikunja's API decodes uploaded avatar and project-background images without a size limit, so a small file can expand into a very large image during decode and resize. An attacker can exhaust server memory and CPU, causing a denial of service.","severity":"high","cvss":7.1,"epss":0.00436,"exploited":false,"exploited_at":null,"products":[{"name":"code.vikunja.io/api","fixed":[],"affected":"all versions","ecosystem":"go"}],"ecosystems":["go"],"tags":["go","package","self-hosted","vikunja"],"not_affected_if":["on-v2.6.0-or-later"],"how_to_check":"Run `go list -m code.vikunja.io/api` in the project or check go.mod for a version below v2.6.0. Deployed binaries: unknown.","fix":"Upgrade code.vikunja.io/api to v2.6.0 or later.","status":"open","published_at":"2026-09-15T16:17:53+00:00","first_seen_at":"2026-10-23T19:13:08+00:00","triaged_at":"2026-10-23T21:45:51+00:00","updated_at":"2026-10-23T21:45:51+00:00","category":"package","confidence":0.7,"triage":{"at":"2026-10-23T21:45:51Z","model":"claude-haiku-5-5","output":{"fix":"Upgrade code.vikunja.io/api to v2.6.0 or later.","reach":"unknown","impact":"medium","summary":"Vikunja's API decodes uploaded avatar and project-background images without a size limit, so a small file can expand into a very large image during decode and resize. An attacker can exhaust server memory and CPU, causing a denial of service.","category":"package","who_cares":["vikunja","go","self-hosted"],"confidence":0.7,"needs_auth":"unknown","worst_case":"Server memory and CPU exhausted by crafted images, causing denial of service.","analyst_note":"","how_to_check":"Run `go list -m code.vikunja.io/api` in the project or check go.mod for a version below v2.6.0. Deployed binaries: unknown.","needs_analyst":false,"not_affected_if":["on-v2.6.0-or-later"],"user_interaction":"no","needs_special_setup":"unknown","severity_if_unknown":"unknown"},"cost_usd":0.001031,"input_tokens":2968,"output_tokens":1469,"severity_before":"high"},"analyst_status":null,"analyst_note":null,"search":"'-2026':20A,28A,31A '-6717':29A '-91971':21A,32A '/api':18A,35A,151C '/api.':102C '39rq':25A '4vh2':24A 'addit':111C,143C 'advisori':106C 'affect':144C 'amplif':14A,98C 'api':44B 'attack':73B 'automat':117C 'avatar':6A,47B,90C 'background':10A,51B,94C 'caus':80B,127C 'code.vikunja.io':17A,34A,101C,150C 'code.vikunja.io/api':16A,33A,149C 'code.vikunja.io/api.':100C 'contain':110C 'could':114C 'cpu':79B 'cve':19A,30A 'decod':4A,45B,69B,88C 'decode/resize':13A,97C 'denial':82B 'edit':138C 'enabl':12A,96C 'exhaust':75B 'expand':62B 'fals':129C 'false-posit':128C 'file':60B 'ghsa':23A 'ghsa-4vh2-39rq-rq8j':22A 'go':27A,36B,121C 'host':40B 'imag':3A,52B,67B,87C 'larg':66B 'limit':56B 'map':118C 'memori':77B 'modul':122C,145C 'note':103C 'packag':37B 'pleas':135C 'posit':130C 'project':9A,50B,93C 'project-background':8A,49B,92C 'report':109C,131C,141C 'resiz':71B 'rq8j':26A 'scanner':134C 'self':39B 'self-host':38B 'server':76B 'servic':84B 'size':55B 'small':59B 'sourc':105C 'standard':120C 'suggest':136C 'unbound':2A,86C 'upload':11A,46B,95C 'v2.6.0':153C 'version':112C,123C,147C 'vikunja':1A,41B,42B,85C 'vulner':133C 'without':53B","nicknames":[],"mitigations":[],"who_affected":null,"tier":null,"verified":{},"analyst_revisit_at":null,"first_public_at":"2026-09-15T16:17:53+00:00","kev":null,"cvss_vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/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":"govuln","external_id":"GO-2026-6717","url":"https://pkg.go.dev/vuln/GO-2026-6717","severity":null,"published_at":"2026-10-19T21:08:26+00:00","modified_at":"2026-10-19T21:08:26+00:00","first_seen_at":"2026-10-23T19:13:08+00:00","fetched_at":"2026-10-23T19:13:08+00:00","note":null},{"source":"epss","external_id":"CVE-2026-91971","url":"https://api.first.org/data/v1/epss?cve=CVE-2026-91971","severity":null,"published_at":null,"modified_at":null,"first_seen_at":"2026-10-23T19:13:43+00:00","fetched_at":"2026-10-23T19:13:43+00:00","note":null},{"source":"nvd","external_id":"CVE-2026-91971","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-91971","severity":null,"published_at":"2026-09-15T16:17:53+00:00","modified_at":"2026-09-21T19:17:16+00:00","first_seen_at":"2026-10-23T19:35:23+00:00","fetched_at":"2026-10-23T19:35:23+00:00","note":null}],"documents":[],"notice":"Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai"}