PatchTheCVECVE-2026-117556: zchunk before 1.5.5 contains a heap out-of-bounds read vulnerability in read_preface() in src/lib/header.c tha
CVE-2026-117556 is a medium-severity flaw (CVSS 4.3) affecting affected software. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.
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 file whose header ends inside a compressed integer, causing reads past the heap header buffer and crashing the application.
Why this priority
- No elevated risk signals yet
No fix is published yet: follow the downgrade or mitigation steps.
Risk facts
| CVSS score | 4.3 (Medium) |
| Attack vector | Network (remote) |
| Attack complexity | Low |
| Privileges needed | None |
| User interaction | Required |
| EPSS exploit chance | n/a |
| CISA exploited list | No |
| Weakness | CWE-125 |
| Published | 2026-10-27 |
| Last modified | 2026-10-27 |
Last updated 2026-10-27 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score
Timeline
- Published CVE record published
- Updated Record last modified
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.
Quick answers
How do I fix CVE-2026-117556?
No fixed release is listed yet. Watch the vendor advisory and apply any mitigation shown on this page.
Is CVE-2026-117556 being exploited?
CVE-2026-117556 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.
What does CVE-2026-117556 affect?
CVE-2026-117556 affects affected software. Severity is medium (CVSS 4.3). 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 file
How urgent is CVE-2026-117556?
Priority 15/100. No elevated risk signals yet.