CVE-2026-55206
CPU exhaustion (DoS) in py7zr via crafted .7z numstreams header.
Is CVE-2026-55206 being exploited?
Not confirmed. CVE-2026-55206 does not appear in CISA's Known Exploited Vulnerabilities catalog, which records only exploitation that has been observed and reported publicly. That is evidence of absence of a report, not evidence the flaw is unattacked. EPSS currently estimates a 0.32% probability of exploitation in the next 30 days.
How severe is CVE-2026-55206?
CVE-2026-55206 is rated High with a CVSS score of 8.7. Severity describes how bad exploitation would be, not how likely it is: pair it with exploitation evidence before deciding what to patch first.
Is there a patch for CVE-2026-55206?
Yes. A fix has been recorded for CVE-2026-55206. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-55206 affect?
CVE-2026-55206 affects py7zr < 1.1.3, Python applications using py7zr, Services processing untrusted .7z archives. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-55206?
Upgrade py7zr to >=1.1.3 and sandbox/validate untrusted .7z processing.
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Crafted .7z archives can trigger O(n^2) behavior in py7zr during SevenZipFile.init(), causing high CPU and denial of service.
Patch when possible
- affected< 1.1.3
As published in the CVE Program record. A version outside these ranges is not a statement that it is unaffected — vendors sometimes understate a range, and distribution-backported builds carry upstream numbers that do not reflect what was patched into them.