CVE-2026-21900
Out-of-bounds heap read in CryptoLib JSON parsing; fixed in v1.4.3.
Is CVE-2026-21900 being exploited?
Not confirmed. CVE-2026-21900 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 0.58% probability of exploitation in the next 30 days.
How severe is CVE-2026-21900?
CVE-2026-21900 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-2026-21900?
Yes. A fix has been recorded for CVE-2026-21900. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.
What does CVE-2026-21900 affect?
CVE-2026-21900 affects CryptoLib, core Flight System (cFS) SDLS-EP, KMC server JSON parser. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.
What should I do about CVE-2026-21900?
Upgrade to v1.4.3 or newer
Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.
Info disclosure or crash via out-of-bounds heap read during JSON parsing; could read heap data.
Patch when possible
- affected< 1.4.3
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.