CVE-2023-29197 — psr7
MEDIUMCVE-2023-29197 is a medium-severity (CVSS 5.3) CWE-436 vulnerability in guzzlehttp/psr7. 1 public exploit or proof-of-concept reference is indexed, so weaponization risk is real. A fix is available for guzzlehttp/psr7 — see the affected versions and patch details below.
Improper header name validation in guzzlehttp/psr7
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
guzzlehttp/psr7🐘guzzlehttp/psr7Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Packagist packages — download data is not available via public APIs for these ecosystems.
Description
guzzlehttp/psr7 is a PSR-7 HTTP message library implementation in PHP. Affected versions are subject to improper header parsing. An attacker could sneak in a newline (\n) into both the header names and values. While the specification states that \r\n\r\n is used to terminate the header list, many servers in the wild will also accept \n\n. This is a follow-up to CVE-2022-24775 where the fix was incomplete. The issue has been patched in versions 1.9.1 and 2.4.5. There are no known workarounds for this vulnerability. Users are advised to upgrade.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐘Packagist | guzzlehttp/psr7 | all versions | 1.9.1composer require guzzlehttp/psr7:^1.9.1 |
| 🐘Packagist | guzzlehttp/psr7 | ≥ 2.0.0&&< 2.4.5 | 2.4.5composer require guzzlehttp/psr7:^2.4.5 |
Affected Products
fedorafedoraprojectpsr-7guzzlephpResearch use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for guzzlehttp/psr7, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update guzzlehttp/psr7 to 1.9.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2023-29197 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.
Frequently Asked Questions
Is CVE-2023-29197 in your dependencies?
Find it across Packagist, including transitive dependencies.