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CVE Record

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

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.

MediumCVSS 4.7Not KEV-listedUpdated
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Glexia's TakeAutomated analysismoderate

Security readout for executives and security teams

Plain-English summary

CVE-2026-21899 is a crash-risk bug in NASA CryptoLib before 1.4.3. A malformed empty Base64url value can trigger an out-of-bounds read during decoding. Business urgency is highest for organizations using CryptoLib in spacecraft-to-ground communications or related test environments. The vendor reports the issue is fixed in version 1.4.3.

Executive priority

Treat as a targeted operational reliability issue, not a broad internet emergency. Patch promptly where CryptoLib protects mission communications or critical test infrastructure. The main business risk is service disruption or instability in specialized space communication workflows.

Technical view

In CryptoLib base64urlDecode, padding-stripping reads input[inputLen - 1] before confirming inputLen > 0 or input is non-NULL. For zero-length input this can read input[-1], and with NULL plus zero length it can dereference NULL - 1. The CVE is CWE-125 with CVSS 4.7, requiring high privileges and network access per the supplied vector.

Likely exposure

Exposure appears limited to deployments using NASA CryptoLib versions earlier than 1.4.3, especially SDLS-EP implementations securing cFS spacecraft and ground-station communications. Systems not using CryptoLib or already on 1.4.3 are not indicated as affected by the provided sources.

Exploitation context

The source bundle does not show CISA KEV listing or active exploitation. The CVSS vector indicates network reachability, low attack complexity, no user interaction, and high privileges required. Expected impact is limited confidentiality, integrity, and availability impact, with process crash called out as the primary consequence.

Researcher notes

Evidence is limited to the CVE record, GitHub advisory, and v1.4.3 release reference. The advisory identifies the faulty bounds check and patch version but the bundle does not provide broader exploit telemetry. Avoid assuming affected downstream products unless they are confirmed to embed CryptoLib before 1.4.3.

Mitigation direction

  • Upgrade NASA CryptoLib to version 1.4.3 or later.
  • Review vendor advisory and release notes before deploying the update.
  • Prioritize mission, test, and ground systems that parse external Base64url input.
  • If immediate upgrade is blocked, seek vendor guidance for supported mitigations.

Validation and detection

  • Inventory systems and builds that include NASA CryptoLib.
  • Confirm deployed CryptoLib versions are 1.4.3 or later.
  • Identify code paths that call base64urlDecode on externally influenced input.
  • Review logs for unexplained CryptoLib process crashes around decoding operations.
  • Track remediation status for all spacecraft, ground, and test environments.
Prepared
Confidence
high
Sources
4

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.

ATT&CK lookup starting points

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cwe · low confidence lookup

CWE-125: Exact CWE lookup

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cve · low confidence lookup

CVE-2026-21899 mapping review

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Vulnerability profileCVE Program record
Severity
Medium
CVSS
4.7 (3.1)
Known Exploited
No
Published

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

Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

1CVSS vectors
0Timeline events
0ADP providers
3Source links

CVSS vector scores

1 official score

We collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.

ScoreVersionSeverityVectorExploitImpactSource
4.7CVSS 3.1MediumCVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:L/I:L/A:L1.23.4Primary CVE score

Vulnerability scoring details

Base CVSS 3.1 score

4.7Medium
CVSS 3.1 vector shape for CVE-2026-21899Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

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

Attack Vector
NetworkAdjacentLocalPhysical
Attack Complexity
LowHigh
Privileges Required
NoneLowHigh
User Interaction
NoneRequired
Scope
ChangedUnchanged
Confidentiality Impact
HighLowNone
Integrity Impact
HighLowNone
Availability Impact
HighLowNone

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
nasaCryptoLib< 1.4.3Listed
Weakness

CWE details

CWE-125

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.

CWE-125 · source CWE mapping

Out-of-bounds Read

Out-of-bounds Read represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.

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