CVE-2025-59148: Oisf Suricata DOS Vulnerability

CVE-2025-59148 Overview

CVE-2025-59148 is a Null Pointer Dereference vulnerability affecting Suricata, the popular open-source network Intrusion Detection System (IDS), Intrusion Prevention System (IPS), and Network Security Monitoring (NSM) engine developed by the Open Information Security Foundation (OISF) and the Suricata community. Versions 8.0.0 and below incorrectly handle the entropy keyword when not anchored to a "sticky" buffer, which can lead to a segmentation fault and denial of service.

Critical Impact

An attacker can remotely trigger a segmentation fault in Suricata by exploiting improper handling of the entropy keyword, causing the IDS/IPS to crash and potentially leaving network traffic unmonitored.

Affected Products

• OISF Suricata 8.0.0
• OISF Suricata 8.0.0-beta1
• OISF Suricata 8.0.0-rc1

Discovery Timeline

• 2025-10-01 - CVE-2025-59148 published to NVD
• 2025-10-06 - Last updated in NVD database

Technical Details for CVE-2025-59148

Vulnerability Analysis

This vulnerability exists in Suricata's entropy detection mechanism, specifically in the detect-entropy.c component. The issue occurs when the entropy keyword in a Suricata rule is not properly anchored to a "sticky" buffer. In this scenario, the entropy matcher attempts to operate without a properly initialized flow variable index (fv_idx), leading to a null pointer dereference when the code tries to access an uninitialized memory location.

The vulnerability is network-exploitable without requiring authentication or user interaction. When triggered, it causes a segmentation fault that crashes the Suricata process, effectively disabling network security monitoring until the service is restarted. This represents a significant risk for organizations relying on Suricata for network intrusion detection, as attackers could disable the IDS before launching additional attacks.

Root Cause

The root cause lies in the DetectEntropySetup function in src/detect-entropy.c. When a rule uses the entropy keyword without being anchored to a sticky buffer (i.e., when s->init_data->list == DETECT_SM_LIST_NOTSET), the code path failed to register a default flow variable. This left the fv_idx field uninitialized, and subsequent calls to the DetectEntropyDoMatch function would attempt to dereference a null pointer when accessing flow-related data structures.

Attack Vector

An attacker can exploit this vulnerability by crafting or triggering rules that use the entropy keyword without proper sticky buffer anchoring. This can be achieved through:

1. Malicious Rule Injection: If an attacker can influence rule files loaded by Suricata
2. Triggering Vulnerable Rules: Network traffic that matches improperly configured entropy-based rules
3. Configuration Exploitation: Leveraging misconfigured detection rules in production environments

The following patch from the OISF team demonstrates the fix applied in version 8.0.1:

 
     int sm_list = DETECT_SM_LIST_PMATCH;
     if (s->init_data->list != DETECT_SM_LIST_NOTSET) {
+        /* sticky buffer */
         if (DetectBufferGetActiveList(de_ctx, s) == -1)
             goto error;
 
         sm_list = s->init_data->list;
         ded->fv_idx = VarNameStoreRegister(
                 DetectEngineBufferTypeGetNameById(de_ctx, sm_list), VAR_TYPE_FLOW_FLOAT);
+    } else {
+        ded->fv_idx = VarNameStoreRegister("content", VAR_TYPE_FLOW_FLOAT);
     }
 
     if (SCSigMatchAppendSMToList(de_ctx, s, DETECT_ENTROPY, (SigMatchCtx *)ded, sm_list) != NULL) {

Source: GitHub Commit Update

The function signature was also updated to include the flow parameter:

 
void DetectEntropyRegister(void);
bool DetectEntropyDoMatch(DetectEngineThreadCtx *det_ctx, const Signature *s,
-        const SigMatchCtx *ctx, const uint8_t *buffer, const uint32_t buffer_len);
+        const SigMatchCtx *ctx, Flow *flow, const uint8_t *buffer, const uint32_t buffer_len);
 
#endif

Source: GitHub Commit Update

Detection Methods for CVE-2025-59148

Indicators of Compromise

• Unexpected Suricata process crashes or restarts with segmentation fault errors
• Log entries showing SIGSEGV signals in Suricata error logs
• Core dumps generated by the Suricata process containing references to detect-entropy.c
• Gaps in network monitoring logs indicating IDS/IPS downtime

Detection Strategies

• Monitor Suricata process stability and implement automated alerting for unexpected service terminations
• Review Suricata rules for entropy keyword usage that is not anchored to sticky buffers
• Implement process monitoring to detect rapid restart cycles of the Suricata daemon
• Analyze core dumps for signatures matching the null pointer dereference in entropy detection code

Monitoring Recommendations

• Configure SentinelOne Singularity to monitor Suricata process health and alert on crashes
• Set up log aggregation to capture and analyze Suricata error logs for segmentation faults
• Implement network monitoring redundancy to maintain visibility if Suricata becomes unavailable
• Enable automated service restart with alerting to minimize detection gaps during exploitation attempts

How to Mitigate CVE-2025-59148

Immediate Actions Required

• Upgrade Suricata to version 8.0.1 or later immediately
• Audit all active Suricata rules for usage of the entropy keyword without sticky buffer anchoring
• Disable rules using the entropy keyword until the patch can be applied
• Implement process monitoring to detect and alert on Suricata crashes

Patch Information

OISF has released version 8.0.1 to address this vulnerability. The fix ensures that the entropy matcher properly registers a default flow variable index when not using a sticky buffer, preventing the null pointer dereference. The patch is available through the official Suricata repositories and can be reviewed in the GitHub Commit Update. For detailed release information, see the Suricata Release Announcement.

Workarounds

• Disable all rules that use the entropy keyword until patching is possible
• Validate that any rules using the entropy keyword are properly anchored to a sticky buffer
• Implement automated Suricata restart mechanisms to minimize downtime in case of crashes
• Deploy redundant IDS/IPS instances to maintain network visibility during potential exploitation

# Configuration example
# Identify rules using the entropy keyword
grep -r "entropy:" /etc/suricata/rules/ | grep -v "#"

# Disable vulnerable rules by commenting them out or removing from rule files
# Alternatively, ensure all entropy keywords are anchored to sticky buffers
# Example of proper anchoring:
# alert http any any -> any any (msg:"Example"; http.request_body; entropy:>7.5; sid:1000001;)

# Restart Suricata after rule modifications
systemctl restart suricata