{"id":"CVE-2026-117556","title":"zchunk before 1.5.5 Heap Out-of-Bounds Read via read_preface()","summary":"zchunk before 1.5.5 contains a heap out-of-bounds read vulnerability in read_preface() in src/lib/header.c that passes the total header length instead of remaining bytes to compint parsing functions. Attackers can supply a crafted .zck f…","severity":"medium","cvss":4.3,"cvssVector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:L","cvssSource":"cna","cwe":["CWE-125"],"vendor":"zchunk","product":"zchunk","affected":["zchunk < 1.5.5"],"ssvc":{"exploitation":"none","automatable":"yes","technicalImpact":"partial","timestamp":"2026-10-28T15:54:22.919848Z"},"published":"2026-10-27","updated":"2026-10-28","sourceUpdated":"2026-10-28T16:17:15.487Z","source":"CVEORG","sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-117556","references":[{"url":"https://github.com/zchunk/zchunk/issues/119","label":"GitHub Issue #119"},{"url":"https://github.com/zchunk/zchunk"},{"url":"https://github.com/zchunk/zchunk/commit/02b371a64bf98245df97315d07c684a0ca5ea1df"},{"url":"https://github.com/zchunk/zchunk/releases/tag/1.5.5","label":"zchunk 1.5.5 Release Notes"},{"url":"https://github.com/zchunk/zchunk/blob/1.5.4/src/lib/header.c#L167"},{"url":"https://www.vulncheck.com/advisories/zchunk-before-1.5.5-heap-out-of-bounds-read-via-read-preface","label":"VulnCheck Advisory: zchunk before 1.5.5 Heap Out-of-Bounds Read via read_preface()"}],"tags":["cve.org"],"epss":0.00328,"epssPercentile":0.2582,"ingestedAt":"2026-10-27T16:11:59.334Z","slug":"CVE-2026-117556","body":"## Overview\n\nzchunk before 1.5.5 contains a heap out-of-bounds read vulnerability in read_preface() in src/lib/header.c that passes the total header length instead of remaining bytes to compint parsing functions. Attackers can supply a crafted .zck file whose header ends inside a compressed integer, causing reads past the heap header buffer and crashing the application.\n\n## Affected\n\n- `zchunk < 1.5.5`\n\n## Remediation\n\nRefer to the linked advisories for vendor-supplied fixes and affected version ranges.","depth":"sunlit","depthScore":24,"depthScoreParts":{"impact":23.7,"likelihood":0.1,"exploitation":0,"ransomware":0},"changes":[]}