CVE-2023-29530 is a high-severity (CVSS 7.5) Improper Input Validation vulnerability in laminas/laminas-diactoros. A fix is available for laminas/laminas-diactoros — see the affected versions and patch details below.
Laminas Diactoros vulnerable to HTTP Multiline Header Termination
Exploitation Status
No confirmed exploitation observed yet
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
- 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-2023-29530.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
CVE-2023-29530 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 378,156 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
laminas/laminas-diactoros🐘laminas/laminas-diactoros🐘laminas/laminas-diactoros🐘laminas/laminas-diactoros🐘laminas/laminas-diactoros🐘laminas/laminas-diactoros🐘laminas/laminas-diactoros🐘laminas/laminas-diactorosReal-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
Impact
Affected versions of Laminas Diactoros accepted a single line feed (LF / \n ) character at the end of a header name. When serializing such a header name containing a line-feed into the on-the-wire representation of a HTTP/1.x message, the resulting message would be syntactically invalid, due to the header line being terminated too early. An attacker that is able to control the header names that are passed to Laminas Diactoros would be able to intentionally craft invalid messages, possibly causing application errors or invalid HTTP requests being sent out with an PSR-18 HTTP client. The latter might present a denial of service vector if a remote service’s web application firewall bans the application due to the receipt of malformed requests.
Patches
The problem has been patched in the following versions:
- 2.18.1
- 2.19.1
- 2.20.1
- 2.21.1
- 2.22.1
- 2.23.1
- 2.24.2
- 2.25.2
Workarounds
Validate HTTP header keys and/or values, and if using user-supplied values, filter them to strip off leading or trailing newline characters before calling withHeader().
References
- CVE-2023-29197
- GHSA-wxmh-65f7-jcvw
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐘Packagist | laminas/laminas-diactoros | all versions | 2.18.1composer require laminas/laminas-diactoros:^2.18.1 |
| 🐘Packagist | laminas/laminas-diactoros | ≥ 2.19.0&&< 2.19.1 | 2.19.1composer require laminas/laminas-diactoros:^2.19.1 |
| 🐘Packagist | laminas/laminas-diactoros | ≥ 2.20.0&&< 2.20.1 | 2.20.1composer require laminas/laminas-diactoros:^2.20.1 |
| 🐘Packagist | laminas/laminas-diactoros | ≥ 2.21.0&&< 2.21.1 | 2.21.1composer require laminas/laminas-diactoros:^2.21.1 |
| 🐘Packagist | laminas/laminas-diactoros | ≥ 2.22.0&&< 2.22.1 | 2.22.1composer require laminas/laminas-diactoros:^2.22.1 |
| 🐘Packagist | laminas/laminas-diactoros | ≥ 2.23.0&&< 2.23.1 | 2.23.1composer require laminas/laminas-diactoros:^2.23.1 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for laminas/laminas-diactoros, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update laminas/laminas-diactoros to 2.18.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2023-29530 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.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2023-29530 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2023-29530. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2023-29530 in your dependencies?
O3 Security finds CVE-2023-29530 across Packagist dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.