Security readout for executives and security teams
Plain-English summary
CVE-2026-21900 affects NASA CryptoLib before 1.4.3, used to secure spacecraft-to-ground communications with SDLS-EP. A malformed KMC server metadata response can trigger an out-of-bounds heap read during encryption metadata parsing. The main documented impact is availability disruption. Public sources state it is patched in 1.4.3; no active exploitation is indicated in the provided sources.
Executive priority
Treat as a high-priority availability risk for mission communication systems using affected CryptoLib versions. Patch planning should be prompt, especially where KMC metadata is processed in production. No source-provided evidence indicates active exploitation, so urgency should be driven by operational criticality and exposure.
Technical view
In cryptography_encrypt(), CryptoLib parses JSON metadata from KMC server responses using a flawed strtok iteration pattern. The pattern can advance one byte past the allocated buffer when processing short or malformed metadata, causing CWE-125 out-of-bounds read. The CVSS v4.0 score is 8.2 high, with network attack vector, low complexity, no privileges, no user interaction, and high availability impact.
Likely exposure
Organizations using NASA CryptoLib versions earlier than 1.4.3, especially in cFS spacecraft or ground-station communication stacks using SDLS-EP and KMC server responses, may be exposed. Exposure depends on whether cryptography_encrypt() processes KMC metadata in deployed workflows.
Exploitation context
The CVSS vector indicates network reachability, low attack complexity, no privileges, and no user interaction, but a prerequisite attack condition is present. Sources do not report public exploitation or KEV listing. The documented consequence is availability impact from malformed or short metadata handling, not confirmed data disclosure or code execution.
Researcher notes
The vulnerability is a CWE-125 heap out-of-bounds read in metadata parsing, fixed by NASA CryptoLib commit 2372efd3 and released in v1.4.3. Analysis should focus on affected call paths, KMC response trust boundaries, and malformed metadata handling. Avoid assuming impacts beyond the published CVSS availability finding.
Mitigation direction
- Upgrade NASA CryptoLib to version 1.4.3 or later.
- Review the GitHub security advisory and release notes before deployment.
- Prioritize systems processing KMC server metadata in operational communication paths.
- If immediate upgrade is not possible, follow vendor guidance for compensating controls.
Validation and detection
- Inventory all CryptoLib deployments and embedded copies.
- Confirm deployed CryptoLib versions are 1.4.3 or later.
- Identify whether cryptography_encrypt() processes KMC metadata in your environment.
- Review logs for unexplained crashes during KMC metadata handling.
- Validate remediation against the vendor advisory and release tag.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
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
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
CWE-125: Exact CWE lookup
Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupCVE-2026-21900 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- High
- CVSS
- 8.2 (4.0)
- Known Exploited
- No
- Published
Vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
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.
CVSS vector scores
1 official scoreWe 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.
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N——Primary CVE scoreVulnerability scoring details
Base CVSS 4.0 score
8.2HighVector: CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
Source materials
- CVE List V5 sourceCVE List V5
- https://github.com/nasa/CryptoLib/security/advisories/GHSA-4g6v-36fv-qcvwCVE reference · x_refsource_CONFIRM
- https://github.com/nasa/CryptoLib/commit/2372efd3da1ccb226b4297222e25f41ecc84821dCVE reference · x_refsource_MISC
- https://github.com/nasa/CryptoLib/releases/tag/v1.4.3CVE reference · x_refsource_MISC
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.
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.