# CVE-2026-21900: CryptoLib Has Out-of-Bounds Read in KMC Encrypt Metadata Parsing via Flawed strtok Pattern

> An out-of-bounds heap read in CryptoLib allows attackers to disclose memory or cause denial of service via malformed KMC metadata.

- **Severity:** High 8.2 (`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`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 10 Jan 2026
- **Updated:** 13 Jan 2026
- **Also known as:** GHSA-4g6v-36fv-qcvw

## What is CVE-2026-21900?

CVE-2026-21900 is a high-severity memory corruption vulnerability in nasa CryptoLib, published on 10 Jan 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### 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, 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.

Weakness: CWE-125 (Out-of-bounds Read)

## Which versions are affected by CVE-2026-21900?

It affects 1 product.


Products: Nasa Cryptolib.

## How do I fix CVE-2026-21900?

No fix has been published for CVE-2026-21900 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-21900 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-21900 exists.

## Other vulnerabilities in nasa CryptoLib

- [CVE-2025-30216](https://insights.sbomify.com/CVE-2025-30216/): CryptoLib Has Heap Overflow in Crypto_TM_ProcessSecurity due to Unchecked Secondary Header Length (critical 9.4)
- [CVE-2025-30356](https://insights.sbomify.com/CVE-2025-30356/): Heap Buffer Overflow via Incomplete Length Check in `Crypto_TC_ApplySecurity` (critical 9.3)
- [CVE-2025-29909](https://insights.sbomify.com/CVE-2025-29909/): CryptoLib's Crypto_TC_ApplySecurity() Has a Heap Buffer Overflow Vulnerability (high 8.9)
- [CVE-2025-29911](https://insights.sbomify.com/CVE-2025-29911/): CryptoLib Has Heap Buffer Overflow in Crypto_AOS_ProcessSecurity Function (high 8.9)
- [CVE-2025-29912](https://insights.sbomify.com/CVE-2025-29912/): CryptoLib Has Heap Buffer Overflow Due to Unsigned Integer Underflow in Crypto_TC_ProcessSecurity (high 8.9)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-21900 and fix it if it is affected.

What it is: CVE-2026-21900 is a high-severity memory corruption vulnerability in nasa CryptoLib, published on 10 Jan 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-21900 exists.

Affected product: nasa CryptoLib. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-21900/ (Markdown: https://insights.sbomify.com/CVE-2026-21900/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-21900
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-21900
- OSV: https://osv.dev/vulnerability/CVE-2026-21900

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From sbomify Insights: https://insights.sbomify.com/CVE-2026-21900/
Summaries are generated and may contain mistakes; the official description above is the record.