# [HIGH] High severity vulnerability found in libcurl and curl (CVE-2023-38545)

**Source:** Snyk
**Published:** 2023-10-04
**Article:** https://snyk.io/blog/curl-high-severity-vulnerability-oct-2023/

## Threat Profile

Snyk Blog In this article
Written by Hadas Bloom 
Tal Dromi 
Micah Silverman 
October 4, 2023
0 mins read Update: October 11, 2023 Today, at 06:00 UTC, the maintainers of cURL released the 8.4.0 versions of curl and libcurl to mitigate a High severity, heap-based buffer overflow ( proof-of-concept and the initial notification ) that could impact systems with a specific configuration and preconditions.
This zero-day vulnerability is present in packages from several managed and unmanaged open sour…

## Indicators of Compromise (high-fidelity only)

- **CVE:** `CVE-2023-38545`
- **CVE:** `CVE-2023-38546`

## MITRE ATT&CK Techniques

- **T1190** — Exploit Public-Facing Application
- **T1204.002** — User Execution: Malicious File
- **T1203** — Exploitation for Client Execution

## Kill chain phases observed

_(none detected from narrative keywords)_

## Recommended hunts

### Curl invoked with SOCKS5-hostname resolution (CVE-2023-38545 exploit precondition)

`UC_1365_2` · phase: **exploit** · confidence: **Medium** · AI-generated for this article

**Splunk SPL (CIM):**
```spl
| tstats `summariesonly` count min(_time) as firstTime max(_time) as lastTime from datamodel=Endpoint.Processes where (Processes.process_name="curl.exe" OR Processes.process_name="curl") AND (Processes.process="*--socks5-hostname*" OR Processes.process="*socks5h://*" OR Processes.process="*-x socks5h*") by Processes.dest Processes.user Processes.parent_process_name Processes.process_name Processes.process Processes.process_hash | `drop_dm_object_name(Processes)` | `security_content_ctime(firstTime)` | `security_content_ctime(lastTime)`
```

**Defender KQL:**
```kql
DeviceProcessEvents
| where Timestamp > ago(7d)
| where FileName =~ "curl.exe" or FileName =~ "curl"
| where ProcessCommandLine has_any ("--socks5-hostname", "socks5h://", "-x socks5h", "--proxy socks5h")
| where AccountName !endswith "$"
| project Timestamp, DeviceName, AccountName, FileName, FolderPath, ProcessCommandLine,
          InitiatingProcessFileName, InitiatingProcessCommandLine, SHA256
| order by Timestamp desc
```

### Vulnerable libcurl/curl version present on host (CVE-2023-38545)

`UC_1365_3` · phase: **recon** · confidence: **High** · AI-generated for this article

**Defender KQL:**
```kql
DeviceTvmSoftwareVulnerabilities
| where CveId == "CVE-2023-38545"
| join kind=leftouter (DeviceTvmSoftwareInventory | project DeviceId, SoftwareName, SoftwareVersion, SoftwareVendor) on DeviceId, SoftwareName
| project Timestamp, DeviceId, DeviceName, OSPlatform, SoftwareVendor, SoftwareName, SoftwareVersion, VulnerabilitySeverityLevel, RecommendedSecurityUpdate
| order by Timestamp desc
```

### Article-specific behavioural hunt — High severity vulnerability found in libcurl and curl (CVE-2023-38545)

`UC_1365_1` · phase: **install** · confidence: **High**

**Splunk SPL (CIM):**
```spl
``` Article-specific bespoke detection — High severity vulnerability found in libcurl and curl (CVE-2023-38545) ```
| tstats `summariesonly` count
    from datamodel=Endpoint.Filesystem
    where Filesystem.action IN ("created","modified")
      AND (Filesystem.file_path="*/usr/bin/curl*" OR Filesystem.file_path="*/usr/local/bin/curl*" OR Filesystem.file_path="*/opt/homebrew/opt/curl*")
    by Filesystem.dest, Filesystem.user, Filesystem.process_name,
       Filesystem.file_path, Filesystem.file_name
| `drop_dm_object_name(Filesystem)`
```

**Defender KQL:**
```kql
// Article-specific bespoke detection — High severity vulnerability found in libcurl and curl (CVE-2023-38545)
// Hunts the actual binaries / paths / commandline fragments named
// in the article instead of a generic technique-class template.

// File-creation events for the named binaries / paths
DeviceFileEvents
| where Timestamp > ago(30d)
| where ActionType in ("FileCreated","FileModified")
| where (FolderPath has_any ("/usr/bin/curl", "/usr/local/bin/curl", "/opt/homebrew/opt/curl"))
| project Timestamp, DeviceName, AccountName, FolderPath,
          FileName, ActionType, InitiatingProcessFileName,
          InitiatingProcessCommandLine
| order by Timestamp desc
```

### IOC-driven hunts (use shared templates)

These are standard IOC-substitution hunts — the canonical SPL and KQL live once in [`_TEMPLATES.md`](../_TEMPLATES.md), so we don't repeat the same boilerplate on every CVE / hash / network-IOC briefing.

- **Asset exposure — vulnerability matches article CVE(s)** ([template](../_TEMPLATES.md#asset-exposure)) — phase: **recon**, confidence: **High**
  - CVE(s): `CVE-2023-38545`, `CVE-2023-38546`


## Why this matters

Severity classified as **HIGH** based on: CVE present, 4 use case(s) fired, 3 technique(s) inferred. Read the full article for actor attribution, tooling details, and any defanged IOCs in the body that aren't visible in the RSS summary.