Vulnerability · Published Jan 10, 2026 · Assigned by GitHub_M

CVE-2026-21899CryptoLib has an out-of-bounds read and crash vulnerability when decoding an empty Base64url string

Medium 4.7

In plain English

A medium-severity out-of-bounds read in CryptoLib from nasa. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 28% of all known vulnerabilities).

Severity (CVSS 3.1)4.7Medium

Exploit odds (30 days)0.3%top 71.9% of all CVEs

Exploited in the wildNo reportsCISA SSVC: none

Attack toolingNoneno public tooling known

Official 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, 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.

Affected products (as reported)

Vendor	Product	Versions
nasa	CryptoLib	< 1.4.3

Weakness: CWE-125 · Vector: CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:L/I:L/A:L

References

https://github.com/nasa/CryptoLib/security/advisories/GHSA-wc29-5hw7-mpj8 x_refsource_CONFIRM
https://github.com/nasa/CryptoLib/releases/tag/v1.4.3 x_refsource_MISC