CVE-2024-55627 Overview
CVE-2024-55627 is an integer underflow vulnerability in Suricata, the widely-deployed open-source network Intrusion Detection System (IDS), Intrusion Prevention System (IPS), and Network Security Monitoring (NSM) engine. Prior to version 7.0.8, a specially crafted TCP stream can trigger an unsigned integer underflow that leads to a very large buffer overflow during memory initialization with memset. This vulnerability can be exploited remotely over the network without authentication, potentially causing denial of service conditions on affected Suricata deployments.
Critical Impact
Remote attackers can crash Suricata instances by sending malicious TCP traffic, disrupting network security monitoring and intrusion prevention capabilities across the protected network infrastructure.
Affected Products
- OISF Suricata versions prior to 7.0.8
- Suricata deployments configured for TCP stream reassembly
- Network security appliances running vulnerable Suricata versions
Discovery Timeline
- 2025-01-06 - CVE-2024-55627 published to NVD
- 2025-03-31 - Last updated in NVD database
Technical Details for CVE-2024-55627
Vulnerability Analysis
This vulnerability exists within Suricata's streaming buffer utility (src/util-streaming-buffer.c), which handles TCP stream reassembly operations. The flaw stems from improper validation of region intersection calculations and buffer size comparisons that can result in an unsigned integer underflow.
When processing specially crafted TCP streams, the streaming buffer code fails to properly validate boundary conditions before performing memory operations. Specifically, the GrowRegionToSize function does not check whether the requested growth size is actually larger than the current buffer size before calculating the difference for memset initialization. When an unsigned integer underflow occurs during this calculation, the result wraps around to an extremely large positive value, causing memset to attempt zero-filling a massive memory region far beyond the allocated buffer.
The vulnerability is categorized under CWE-122 (Heap-based Buffer Overflow) and CWE-787 (Out-of-bounds Write), reflecting the memory corruption that occurs when the oversized memset operation writes beyond buffer boundaries.
Root Cause
The root cause is twofold: First, the region intersection logic in the streaming buffer incorrectly determines whether data ranges overlap, leading to improper buffer merging decisions. Second, the GrowRegionToSize function lacks a critical safety check to ensure the requested size actually exceeds the current buffer size before computing the size difference for memory initialization.
When calculating diff = grow - region->buf_size where both are unsigned integers, if grow is less than or equal to region->buf_size due to the flawed intersection logic, the subtraction underflows and produces a very large positive number, which is then passed to memset.
Attack Vector
The attack can be executed remotely over the network by sending specially crafted TCP packets that trigger the vulnerable code path in Suricata's stream reassembly engine. No authentication or user interaction is required, making this vulnerability particularly concerning for internet-facing Suricata deployments.
The following patches address the vulnerability:
Region Intersection Fix - Corrects the logic for determining whether data ranges intersect:
SCLogDebug("r %p: %" PRIu64 "/%" PRIu64 " - adjusted %" PRIu64 "/%" PRIu64, r, r->stream_offset,
r->stream_offset + r->buf_size, reg_o, reg_re);
/* check if data range intersects with region range */
- if (offset >= reg_o && offset <= reg_re) {
- SCLogDebug("r %p is in-scope", r);
- return true;
- }
- if (re >= reg_o && re <= reg_re) {
- SCLogDebug("r %p is in-scope: %" PRIu64 " >= %" PRIu64 " && %" PRIu64 " <= %" PRIu64, r, re,
- reg_o, re, reg_re);
- return true;
- }
- SCLogDebug("r %p is out of scope: %" PRIu64 "/%" PRIu64, r, offset, re);
- return false;
+ /* [offset:re] and [reg_o:reg_re] do not intersect if and only if
+ * re < reg_o or if reg_re < offset (one segment is strictly before the other)
+ * trusting that offset<=re and reg_o<=reg_re
+ */
+ if (re < reg_o || reg_re < offset) {
+ return false;
+ }
+ return true;
}
/** \internal
Source: GitHub Commit 282509f
Buffer Growth Validation - Adds check before attempting to grow the region:
} else {
/* using "main", expand to include "next" */
- if (GrowRegionToSize(sb, cfg, start, mem_size) != 0) {
- new_mem_size = new_data_size;
- goto just_main;
+ if (mem_size > start->buf_size) {
+ // Check that start->buf_size is actually not big enough
+ // As mem_size computation and earlier checks do not make it clear.
+ if (GrowRegionToSize(sb, cfg, start, mem_size) != 0) {
+ new_mem_size = new_data_size;
+ goto just_main;
+ }
}
SCLogDebug("start->buf now size %u", mem_size);
Source: GitHub Commit 8900041
Unsigned Underflow Safety Check - Prevents the integer underflow in GrowRegionToSize:
/* try to grow in multiples of cfg->buf_size */
const uint32_t grow = ToNextMultipleOf(size, cfg->buf_size);
SCLogDebug("grow %u", grow);
+ if (grow <= region->buf_size) {
+ // do not try to shrink, and do not memset with diff having unsigned underflow
+ return SC_OK;
+ }
void *ptr = REALLOC(cfg, region->buf, region->buf_size, grow);
if (ptr == NULL) {
Source: GitHub Commit 9a53ec4
Detection Methods for CVE-2024-55627
Indicators of Compromise
- Unexpected Suricata process crashes or restarts, particularly when processing high volumes of TCP traffic
- Segmentation fault errors in system logs referencing util-streaming-buffer.c or memory allocation functions
- Abnormal memory consumption spikes in Suricata processes before crashes
- Core dumps indicating heap corruption or buffer overflows in the streaming buffer module
Detection Strategies
- Monitor Suricata process stability and implement alerting for unexpected daemon restarts
- Review system logs for segmentation faults, memory allocation errors, or heap corruption indicators
- Implement network traffic analysis to detect anomalous TCP stream patterns that may indicate exploitation attempts
- Deploy endpoint detection tools to identify process crashes and memory corruption events on Suricata hosts
Monitoring Recommendations
- Enable verbose logging in Suricata to capture detailed information about stream reassembly operations
- Configure process monitoring to alert on Suricata daemon crashes or abnormal terminations
- Implement memory usage monitoring with thresholds to detect unusual allocation patterns
- Review core dumps when available to identify exploitation attempts against this vulnerability
How to Mitigate CVE-2024-55627
Immediate Actions Required
- Upgrade Suricata to version 7.0.8 or later immediately to address this vulnerability
- Review network architecture to identify all Suricata deployments that require patching
- Implement redundancy for critical Suricata sensors to maintain visibility during potential exploitation
- Consider temporarily increasing monitoring of Suricata process health until patches are deployed
Patch Information
The vulnerability has been fully addressed in Suricata version 7.0.8. The fix consists of three separate commits that correct the region intersection logic, add proper size validation before buffer growth operations, and implement an explicit safety check to prevent unsigned integer underflow.
For detailed patch information, refer to:
Workarounds
- Deploy network segmentation to limit exposure of Suricata management interfaces to untrusted networks
- Implement process monitoring and automatic restart capabilities to maintain availability if crashes occur
- Consider deploying redundant Suricata instances to maintain network visibility during potential exploitation
- Apply network-level rate limiting for TCP connections to reduce the attack surface while awaiting patches
# Verify current Suricata version
suricata --build-info | grep -i version
# Update Suricata on Debian/Ubuntu systems
sudo apt update && sudo apt install suricata
# Restart Suricata after upgrade
sudo systemctl restart suricata
# Verify the new version is running
suricata -V
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
