What is the CVSS score of CVE-2026-21899?

CVE-2026-21899 has a CVSS 3.1 base score of 4.7 (Medium). CVSS vector: CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:L/I:L/A:L. EPSS exploitation probability: 0.0%.

Which versions of Cryptolib are affected by CVE-2026-21899?

CVE-2026-21899 presents moderate security risk, a out-of-bounds read vulnerability rated CVSS 4.7. Exploitation could cause memory corruption or application crashes.

Is there a public PoC exploit available for CVE-2026-21899?

Yes, a public proof-of-concept exploit is available for CVE-2026-21899. Prioritise patching immediately. EPSS: 0.0%.

How to fix or mitigate CVE-2026-21899?

Within 30 days: Identify affected systems and apply vendor patches as part of regular patch cycle. Monitor vendor channels for patch availability.

Cryptolib CVE-2026-21899

MEDIUM

Out-of-bounds Read (CWE-125)

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

Denial Of Service Cryptolib

4.7

CVSS 3.1 · GitHub Advisory

Severity by source

GitHub Advisory PRIMARY

4.7 MEDIUM

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

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

CVSS VectorGitHub Advisory

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

Attack Vector

Network

Attack Complexity

Low

Privileges Required

High

User Interaction

None

Scope

Unchanged

Confidentiality

Low

Integrity

Low

Availability

Low

Lifecycle Timeline

Analysis Generated

Mar 12, 2026 - 21:54 vuln.today

PoC Detected

Jan 15, 2026 - 21:45 vuln.today

Public exploit code

CVE Published

Jan 10, 2026 - 01:16 nvd

MEDIUM 4.7

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, in base64urlDecode, padding-stripping dereferences input[inputLen - 1] before checking that inputLen > 0 or that input != NULL. For inputLen 0, this becomes an OOB read at input[-1], potentially crashing the process. If input NULL and inputLen == 0, it dereferences NULL - 1. This issue has been patched in version 1.4.3.

AnalysisAI

CryptoLib versions prior to 1.4.3 contain an out-of-bounds read vulnerability in the base64urlDecode function that dereferences memory before validating input parameters, potentially causing a denial of service in spacecraft communications secured by SDLS-EP. Affected systems running cFS with vulnerable CryptoLib versions could crash when processing malformed base64 input. Public exploit code exists for this vulnerability, though no patch is currently 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, in base64urlDecode, padding-stripping dereferences input[inputLen - 1] before checking that inputLen > 0 or that input != NULL. For inputLen 0, this becomes an OOB read at input[-1], potentially crashing the process. If input NULL and inpu