What is the CVSS score of CVE-2026-21900?

CVE-2026-21900 has a CVSS 3.1 base score of 5.9 (Medium). CVSS vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H. EPSS exploitation probability: 0.1%.

Which versions of Cryptolib are affected by CVE-2026-21900?

CVE-2026-21900 presents moderate security risk, a out-of-bounds read vulnerability rated CVSS 5.9. Exploitation could cause memory corruption or application crashes.. A patch is available.

Is there a public PoC exploit available for CVE-2026-21900?

Yes, a public proof-of-concept exploit is available for CVE-2026-21900. Prioritise patching immediately. EPSS: 0.1%.

How to fix or mitigate CVE-2026-21900?

Within 30 days: Identify affected systems and apply vendor patches as part of regular patch cycle. Vendor patch is available.

Cryptolib CVE-2026-21900

MEDIUM

Out-of-bounds Read (CWE-125)

2026-01-10 security-advisories@github.com

Buffer Overflow Information Disclosure Cryptolib

5.9

CVSS 3.1 · GitHub Advisory

Severity by source

GitHub Advisory PRIMARY

5.9 MEDIUM

AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H

Primary rating from GitHub Advisory · only source for this CVE.

CVSS VectorGitHub Advisory

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H

Attack Vector

Network

Attack Complexity

High

Privileges Required

None

User Interaction

None

Scope

Unchanged

Confidentiality

None

Integrity

None

Availability

High

Lifecycle Timeline

Analysis Generated

Mar 12, 2026 - 21:54 vuln.today

PoC Detected

Jan 16, 2026 - 16:46 vuln.today

Public exploit code

Patch released

Jan 16, 2026 - 16:46 nvd

Patch available

CVE Published

Jan 10, 2026 - 01:16 nvd

MEDIUM 5.9

DescriptionGitHub Advisory

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.

AnalysisAI

CryptoLib versions prior to 1.4.3 suffer from an out-of-bounds heap read in the cryptography_encrypt() function when processing malformed JSON metadata from KMC servers, allowing remote attackers to trigger a denial of service condition. The vulnerability stems from improper buffer boundary checking during string parsing in spacecraft-ground station communications secured by the SDLS-EP protocol. Public exploit code exists for this medium-severity flaw, though a patch is available.

Technical ContextAI

Classified as CWE-125 (Out-of-bounds Read). Affects Cryptolib. 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