CVE-2024-45614 is a medium-severity (CVSS 5.4) CWE-639 vulnerability in puma. A fix is available for puma — see the affected versions and patch details below.
Header normalization allows for client to clobber proxy set headers in Puma
Exploitation Status
No confirmed exploitation observed yet
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for CVE-2024-45614.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
Where this sits among everything scored
Real-World Exposure
puma💎pumaReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects RubyGems packages — download data is not available via public APIs for these ecosystems.
Description
Impact
Clients could clobber values set by intermediate proxies (such as X-Forwarded-For) by providing a underscore version of the same header (X-Forwarded_For). Any users trusting headers set by their proxy may be affected. Attackers may be able to downgrade connections to HTTP (non-SSL) or redirect responses, which could cause confidentiality leaks if combined with a separate MITM attack.
Patches
v6.4.3/v5.6.9 now discards any headers using underscores if the non-underscore version also exists. Effectively, allowing the proxy defined headers to always win.
Workarounds
Nginx has a underscores_in_headers configuration variable to discard these headers at the proxy level.
Any users that are implicitly trusting the proxy defined headers for security or availability should immediately cease doing so until upgraded to the fixed versions.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 💎RubyGems | puma | all versions | 5.6.9bundle update puma --conservative |
| 💎RubyGems | puma | ≥ 6.0.0&&< 6.4.3 | 6.4.3bundle update puma --conservative |
Affected Products
pumapumaDetection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for puma, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update puma to 5.6.9 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2024-45614 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
Fixing This On Your OS
If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.
This issue is classified as moderate severity rather than important because, while it allows clients to manipulate proxy-set headers like `X-Forwarded-For`, its exploitability depends on specific conditions. The vulnerability only affects applications that rely on these headers for security purposes, such as IP-based…
Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base or stability.Source: Red Hat security advisory for CVE-2024-45614 (CC BY 4.0)
Frequently Asked Questions
Is CVE-2024-45614 in your dependencies?
Find it across RubyGems, including transitive dependencies.