{"id":"CVE-2026-109584","url":"https://www.cyber-defence.io/tools/cve/CVE-2026-109584","generatedAt":"2026-10-28T11:21:37.683Z","title":"Improper Handling of Highly Compressed Data (Data Amplification) vulnerability in the HTTP/2 implementation of mtrudel bandit allows an unauthenticated remote attacker to exhaust server memory via a small HPACK-compressed HEADERS block.","description":"Improper Handling of Highly Compressed Data (Data Amplification) vulnerability in the HTTP/2 implementation of mtrudel bandit allows an unauthenticated remote attacker to exhaust server memory via a small HPACK-compressed HEADERS block. The block stores one large cookie value in the HPACK dynamic table and then references it tens of thousands of times with 1-byte indexed fields. In the reporter's run, a 49 KB block made a server with default settings allocate a 183 MB cookie binary before any application code ran, and every concurrent stream can repeat the cost.\n\nBandit.HTTP2.Connection caps only the compressed block (max_header_block_size), and its check of the decoded list against max_header_list_size never fires because that setting defaults to :infinity. combine_cookie_crumbs/1 in lib/bandit/http2/stream.ex then joins every crumb into one binary.\n\nThis issue affects bandit: from 0.3.3 before 1.14.0.","published":"2026-10-26T14:16:25.000Z","lastModified":"2026-10-26T16:59:16.000Z","status":"Awaiting Analysis","sourceIdentifier":"6b3ad84c-e1a6-4bf7-a703-f496b71e49db","cvss":{"version":"4.0","score":8.7,"severity":"HIGH","vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/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/M"},"cwe":["CWE-409"],"affected":[],"epss":{"score":0.00602,"percentile":0.48612,"date":"2026-10-27","history":[{"date":"2026-10-27","score":0.00602,"percentile":0.48612}]},"kev":{"listed":false},"exploits":{"count":0,"verified":false,"firstPublished":null,"source":"Exploit-DB (https://gitlab.com/exploit-database/exploitdb)","entries":[]},"verdict":{"level":"high","text":"High impact if exploited, but EPSS currently rates exploitation as unlikely (0.60%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit."},"changes":[{"kind":"new","label":"New CVE","at":"2026-10-26T14:16:25.000Z","detail":{"score":"8.7","severity":"HIGH","publishedAt":"2026-10-26T14:16:25.000Z"},"summary":"New CVE, high severity (CVSS 8.7)."}],"references":[{"url":"https://cna.erlef.org/cves/CVE-2026-109584.html","source":"6b3ad84c-e1a6-4bf7-a703-f496b71e49db"},{"url":"https://github.com/mtrudel/bandit/commit/220b9dfd27f9a21305be2afc75cbe585ddc24e7a","source":"6b3ad84c-e1a6-4bf7-a703-f496b71e49db"},{"url":"https://github.com/mtrudel/bandit/commit/44bf969cd59851622fb6ee4d16227fbc39a77fb4","source":"6b3ad84c-e1a6-4bf7-a703-f496b71e49db"},{"url":"https://github.com/mtrudel/bandit/security/advisories/GHSA-7gfj-7gvq-3xqj","source":"6b3ad84c-e1a6-4bf7-a703-f496b71e49db"},{"url":"https://osv.dev/vulnerability/EEF-CVE-2026-109584","source":"6b3ad84c-e1a6-4bf7-a703-f496b71e49db"}],"sources":{"nvd":"https://nvd.nist.gov/vuln/detail/CVE-2026-109584","epss":"https://www.first.org/epss/","kev":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog","exploitdb":"https://www.exploit-db.com/"},"licence":"CC BY 4.0 — link back to the CVE Explorer if you publish the results; upstream data remains subject to its own terms."}