CVE-2026-48109
DoS via crafted MessagePack payload in C# LZ4 decompression
Is CVE-2026-48109 being exploited?
Not confirmed. CVE-2026-48109 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 0.51% probability of exploitation in the next 30 days.
How severe is CVE-2026-48109?
CVE-2026-48109 is rated High with a CVSS score of 8.2. 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-2026-48109?
Yes. A fix has been recorded for CVE-2026-48109. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-48109 affect?
CVE-2026-48109 affects MessagePack for C# library (LZ4 path) < 2.5.301 and < 3.1.7, Pre-2.5.301 and 3.1.7 versions. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-48109?
Upgrade to 2.5.301 or 3.1.7
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Remote attacker can crash or degrade service via out-of-bounds reads during LZ4 decompression; possible memory disclosure.
Patch when possible
- affected>= 3.1.7 and < 3.1.7
- affected< 2.5.301
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.