GHSA-qpgp-93vx-g8v8 CVE-2026-47736
Puma PROXY Protocol v1 Parser Allows Remote Memory Exhaustion
- Severity
- 7.5 / 10
- High · CVSS 3.1
- Exploit chance (EPSS)
- 0.35%
- Chance of exploitation in the next 30 days. Higher than 28.18% of scored vulnerabilities.
- Known exploited
- No
- Not in CISA's catalog
- Weakness
- CWE-400 Uncontrolled Resource Consumption
- Fix
8.0.2- Upgrade puma to this version or later
Description
Impact
PROXY protocol support for Puma was added in version 5.5.0.
When PROXY protocol v1 support is enabled, Puma reads incoming bytes into an internal buffer. It waits for "\r\n" to determine whether a PROXY v1 line is present. If an attacker opens a TCP connection and continuously sends bytes without CRLF, Puma keeps appending to this pre-parse buffer.
This can cause unbounded in-process memory growth and additional CPU cost from repeatedly scanning the growing buffer for CRLF. A single, unauthenticated TCP connection can drive significant memory growth and may cause process/container OOM or degraded availability.
Only Puma servers using the following non-default config are affected:
set_remote_address proxy_protocol: :v1
Patches
Users should upgrade to versions 7.2.1 or 8.0.2.
Workarounds
- Disable PROXY protocol v1 parsing if it is not required:
# remove/comment this:
# set_remote_address proxy_protocol: :v1
- Restrict direct network access to Puma listeners using PROXY protocol:
- Only allow trusted load balancers/reverse proxies to connect.
- Block arbitrary client TCP access with firewall/security group rules.
Resources
Affected versions
RubyGems
How to fix
Move to the fixed version or later with your package manager, update the lockfile, and run your tests. If the package only arrives through another dependency, upgrade that dependency first. If none of its releases pulls a fixed version yet, force the version with your package manager's override.
puma RubyGems → 8.0.2
- bundler
bundle update puma # Gemfile: gem "puma", ">= 8.0.2"
Severity breakdown
CVSS 3.1 7.5
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
- Attack vector
- Network
- Attack complexity
- Low
- Privileges required
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- None
- Integrity
- None
- Availability
- High
Weakness
CWE-400: Uncontrolled Resource Consumption
The product does not properly control the allocation and maintenance of a limited resource.
How to prevent it
- Architecture and Design: Design throttling mechanisms into the system architecture. The best protection is to limit the amount of resources that an unauthorized user can cause to be expended. A strong authentication and access control model will help prevent such attacks from occurring in the first place. The login application should be protected against DoS attacks as much as possible. Limiting the database access, perhaps by caching result sets, can help minimize the resources expended. To further limit the potential for a DoS attack, consider tracking the rate of requests received from users and blocking requests that exceed a defined rate threshold.
- Architecture and Design: Mitigation of resource exhaustion attacks requires that the target system either: recognizes the attack and denies that user further access for a given amount of time, or uniformly throttles all requests in order to make it more difficult to consume resources more quickly than they can again be freed. The first of these solutions is an issue in itself though, since it may allow attackers to prevent the use of the system by a particular valid user. If the attacker impersonates the valid user, they may be able to prevent the user from accessing the server in question. The second solution is simply difficult to effectively institute -- and even when properly done, it does not provide a full solution. It simply makes the attack require more resources on the part of the attacker.
- Architecture and Design: Ensure that protocols have specific limits of scale placed on them.
- Implementation: Ensure that all failures in resource allocation place the system into a safe posture.
References
Packages
Other links
- github.com/puma/puma/security/advisories/GHSA-qpgp-93vx-g8v8
- github.com/rubysec/ruby-advisory-db/blob/master/gems/puma/CVE-2026-47736.yml
- cve.org/CVERecord
- github.com/puma/puma/commit/439c6136d9c2275721b7864db3ee78af7c80889f
- github.com/puma/puma/commit/ebe9db3929ab8299d19c8f5b41e8ef4f4b22fa58
- github.com/puma/puma/releases/tag/v7.2.1
- github.com/puma/puma/releases/tag/v8.0.2
Timeline
- Published
- Last updated by the source
- Latest EPSS score
Related advisories
| Advisory | Severity | Why it's related |
|---|---|---|
| GHSA-2vqw-3mp8-cgmx Puma PROXY Protocol v1 Accepts Repeated Protocol Headers on Persistent Connections | High | Also affects puma |
| GHSA-9hf4-67fc-4vf4 Puma's header normalization allows for client to clobber proxy set headers | Medium | Also affects puma |
| GHSA-c2f4-cvqm-65w2 Puma HTTP Request/Response Smuggling vulnerability | High | Also affects puma |
| GHSA-68xg-gqqm-vgj8 Puma HTTP Request/Response Smuggling vulnerability | Critical | Also affects puma |
| GHSA-h99w-9q5r-gjq9 Puma vulnerable to HTTP Request Smuggling | Critical | Also affects puma |
| GHSA-rmj8-8hhh-gv5h Puma used with Rails may lead to Information Exposure | High | Also affects puma |
| GHSA-48w2-rm65-62xx Puma with proxy which forwards LF characters as line endings could allow HTTP request smuggling | Low | Also affects puma |
| GHSA-q28m-8xjw-8vr5 Puma's Keepalive Connections Causing Denial Of Service | High | Also affects puma |
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