How severe is CVE-2023-30536?

CVE-2023-30536 has a CVSS score of 6.5/10, rated MEDIUM. Review your exposure and patch according to your risk tolerance.

Which packages are affected by CVE-2023-30536?

CVE-2023-30536 affects the following packages: slim/psr7 (Packagist), slim/psr7 (Packagist), slim/psr7 (Packagist). Ecosystems affected: Packagist.

How do I fix CVE-2023-30536?

Update slim/psr7 to 1.6.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2023-30536 is resolved across your whole dependency graph.

How do I detect CVE-2023-30536 in my Packagist dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for slim/psr7, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2023-30536 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-2023-30536 actively exploited in the wild?

Yes. There are 1 known exploit references for CVE-2023-30536, including 1 in-the-wild exploitation observed on GitHub and other sources. Treat this as actively exploitable and prioritize patching immediately. All exploit code should only be run in an isolated sandbox environment for research or authorized testing — never against production systems without explicit written authorization.

What is the EPSS score for CVE-2023-30536?

CVE-2023-30536 has an EPSS (Exploit Prediction Scoring System) score of 0.7%, placing it in the 55th 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-2023-30536?

CVE-2023-30536 is classified as CWE-436 (CWE-436). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2023-30536 published, and has it been updated?

CVE-2023-30536 was published on April 17, 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

MEDIUM severity

CVE-2023-30536 — psr7

MEDIUMFix: slimphp/Slim-Psr7@ed1d553

CVE-2023-30536 is a medium-severity (CVSS 6.5) CWE-436 vulnerability in slim/psr7. 1 public exploit or proof-of-concept reference is indexed, so weaponization risk is real. A fix is available for slim/psr7 — see the affected versions and patch details below.

Insecure header validation in slim/psr7

Also known asGHSA-q2qj-628g-vhfw

Published

Apr 17, 2023

Updated

Oct 28, 2026

Affected

3 pkgs

Patched

3 / 3

Exploits

1 known

Exploitation data as of Nov 8, 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-2023-30536.

EPSS Exploitation Probability

via FIRST.org ↗

0.7%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs55th percentile — riskier than 55% 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

3 pkgs affected

🐘slim/psr7🐘slim/psr7🐘slim/psr7

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

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. An attacker that is able to control the header names that are passed to Slilm-Psr7 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 issue is patched in 1.6.1, 1.5.1, and 1.4.1.

Workarounds

In Slim-Psr7 prior to 1.6.1, 1.5.1, and 1.4.1, 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().

Acknowledgments

We are very grateful to and thank <a href="https://gjcampbell.co.uk/">Graham Campbell</a> for reporting and working with us on this issue.

References

Guzzle: CVE-2023-29197, with advisory GHSA-wxmh-65f7-jcvw
Laminas Diactoros: CVE-2023-29530, with advisory GHSA-xv3h-4844-9h36
https://www.rfc-editor.org/rfc/rfc7230#section-3.2.4

Affected Packages

3 total 3 fixed

Ecosystem	Package	Vulnerable range	Fix
🐘Packagist	`slim/psr7`	≥ 1.6&&< 1.6.1	1.6.1`composer require slim/psr7:^1.6.1`
🐘Packagist	`slim/psr7`	≥ 1.5&&< 1.5.1	1.5.1`composer require slim/psr7:^1.5.1`
🐘Packagist	`slim/psr7`	all versions	1.4.1`composer require slim/psr7:^1.4.1`

Affected Products

1 product · 1 configurations

Application

slim psr-7slimframework

< 1.6.1

range

Exploits & PoCs

Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.

slim/psr7 is a PSR-7 implementation for use with Slim 4. In versions pri…

nvd.nist.govNVDApr 2023

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for slim/psr7, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update slim/psr7 to 1.6.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2023-30536 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 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`. An attacker that is able to control the header names that are passed to Slilm-Psr7 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 t