How severe is CVE-2023-29530?

CVE-2023-29530 has a CVSS score of 7.5/10, rated HIGH. Immediate patching is strongly recommended.

Which packages are affected by CVE-2023-29530?

CVE-2023-29530 affects the following packages: laminas/laminas-diactoros (Packagist), laminas/laminas-diactoros (Packagist), laminas/laminas-diactoros (Packagist), laminas/laminas-diactoros (Packagist), laminas/laminas-diactoros (Packagist), laminas/laminas-diactoros (Packagist), laminas/laminas-diactoros (Packagist), laminas/laminas-diactoros (Packagist). Ecosystems affected: Packagist.

How do I fix CVE-2023-29530?

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.

How do I detect CVE-2023-29530 in my Packagist dependencies?

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.

How do I mitigate CVE-2023-29530 if there is no patch (or I can't update yet)?

Cap what an attacker can consume: apply request size, rate and timeout limits in front of the affected component, and run it with memory and CPU limits so exhaustion degrades one worker rather than the whole service.

Is CVE-2023-29530 actively exploited in the wild?

No public exploit code has been indexed for CVE-2023-29530 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2023-29530?

CVE-2023-29530 has an EPSS (Exploit Prediction Scoring System) score of 1.0%, placing it in the 62th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2023-29530?

CVE-2023-29530 is classified as Improper Input Validation (CWE-20). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2023-29530 published, and has it been updated?

CVE-2023-29530 was published on April 24, 2023 and was last updated on October 28, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

🐘

🐘 Packagist

Not in CISA KEV

HIGH severity

CVE-2023-29530 — laminas-diactoros

HIGHFix: laminas/laminas-diactoros@7e721a6

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

Also known asGHSA-xv3h-4844-9h36

Published

Apr 24, 2023

Updated

Oct 28, 2026

Affected

8 pkgs

Patched

8 / 8

Exploits

None indexed

Exploitation data as of Nov 9, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

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

via FIRST.org ↗

1.0%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs62th percentile — riskier than 62% of all scored CVEsHighest risk

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

8 pkgs affected

🐘laminas/laminas-diactoros🐘laminas/laminas-diactoros🐘laminas/laminas-diactoros🐘laminas/laminas-diactoros🐘laminas/laminas-diactoros🐘laminas/laminas-diactoros🐘laminas/laminas-diactoros🐘laminas/laminas-diactoros

Real-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

8 total 8 fixed

Ecosystem	Package	Vulnerable range	Fix
🐘Packagist	`laminas/laminas-diactoros`	all versions	2.18.1`composer require laminas/laminas-diactoros:^2.18.1`
🐘Packagist	`laminas/laminas-diactoros`	≥ 2.19.0&&< 2.19.1	2.19.1`composer require laminas/laminas-diactoros:^2.19.1`
🐘Packagist	`laminas/laminas-diactoros`	≥ 2.20.0&&< 2.20.1	2.20.1`composer require laminas/laminas-diactoros:^2.20.1`
🐘Packagist	`laminas/laminas-diactoros`	≥ 2.21.0&&< 2.21.1	2.21.1`composer require laminas/laminas-diactoros:^2.21.1`
🐘Packagist	`laminas/laminas-diactoros`	≥ 2.22.0&&< 2.22.1	2.22.1`composer require laminas/laminas-diactoros:^2.22.1`
🐘Packagist	`laminas/laminas-diactoros`	≥ 2.23.0&&< 2.23.1	2.23.1`composer require laminas/laminas-diactoros:^2.23.1`

Affected Products

3 products · 11 configurations

fedorafedoraproject

1 version

Application

laminas-diactorosgetlaminas

< 2.18.1

7 versions

2.19.02.20.02.21.02.22.02.23.02.24.02.25.0

Application

psr-7guzzlephp

≥ 2.0.0 && < 2.4.5

range

Detection & mitigation playbook

Open-source dependency

Detect
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
Cap what an attacker can consume: apply request size, rate and timeout limits in front of the affected component, and run it with memory and CPU limits so exhaustion degrades one worker rather than the whole service.

Frequently Asked Questions

### 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 clien