CVE-2026-21900

CryptoLib Has Out-of-Bounds Read in KMC Encrypt Metadata Parsing via Flawed strtok Pattern

MEDIUM
5.9
CVSS Score
Published: January 10, 2026 at 12:14 AM UTC
Updated: June 17, 2026 at 10:19 AM UTC
1 product affected across 1 vendorCryptoLib

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Severity
MEDIUM5.9
Exploit prediction
EPSS 0.6%
SSVC
PoC

Description

CryptoLib provides a software-only solution using the CCSDS Space Data Link Security Protocol - Extended Procedures (SDLS-EP) to secure communications between a spacecraft running the core Flight System (cFS) and a ground station. Prior to version 1.4.3, an out-of-bounds heap read vulnerability in cryptography_encrypt() occurs when parsing JSON metadata from KMC server responses. The flawed strtok iteration pattern uses ptr + strlen(ptr) + 1 which reads one byte past allocated buffer boundaries when processing short or malformed metadata strings. This issue has been patched in version 1.4.3.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

v < 1.4.3
Affected range stops below 1.4.3, so it looks safe — our inference, not a vendor statement

Remediation

No guide yet

No remediation guidance has been written for this CVE yet. What the record does show:

References (3)

x_refsource_CONFIRMExploitVendor Advisory
Source: cverecord
https://github.com/nasa/CryptoLib/security/advisories/GHSA-4g6v-36fv-qcvw
x_refsource_MISCRelease Notes
Source: cverecord
https://github.com/nasa/CryptoLib/releases/tag/v1.4.3

SSVC — Action Prioritization

SSVCPoCAutomatablePartial impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

Attack Vector
NETWORK
Complexity
HIGH
Privileges
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
NONE
Integrity
NONE
Availability
HIGH
Vector?

Quick Info

StatusANALYZED
CWE
CWE-125

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