CVE-2021-25289
Out of bounds write in Pillow
Executive Summary
CVE-2021-25289 is a critical severity vulnerability affecting binary-analysis. It is classified as an undisclosed flaw. Ensure your systems and dependencies are patched immediately to mitigate exposure risks.
Precogs AI Insight
"The fundamental weakness here is traced back to within An issue, allowing bypassed validation checks on external interactions. An attacker can craft a specific payload to execute arbitrary code on the target system, potentially leading to full system compromise. The Precogs Binary SAST engine detects such memory corruption vulnerabilities to flag these architectural defects instantly."
What is this vulnerability?
CVE-2021-25289 is categorized as a critical Buffer Overflow flaw. Based on our vulnerability intelligence, this issue occurs when the application fails to securely handle untrusted data boundaries.
An issue was discovered in Pillow before 8.1.1. TiffDecode has a heap-based buffer overflow when decoding crafted YCbCr files because of certain interpreta.
This architectural defect enables adversaries to bypass intended security controls, directly manipulating the application's execution state or data layer. Immediate strategic intervention is required.
Risk Assessment
| Metric | Value |
|---|---|
| CVSS Base Score | 9.8 (CRITICAL) |
| Vector String | N/A |
| Published | March 29, 2021 |
| Last Modified | October 8, 2024 |
| Related CWEs | N/A |
Impact on Systems
✅ Remote Code Execution: Attackers can overwrite the instruction pointer (EIP/RIP) to redirect execution to malicious shellcode.
✅ Memory Corruption: Overwriting adjacent memory regions can corrupt critical application state, leading to unpredictable privilege escalation.
✅ Denial of Service: Triggering segmentation faults and kernel panics results in immediate disruption of critical systems.
How to fix this issue?
Implement the following strategic mitigations immediately to eliminate the attack surface.
1. Memory-Safe Languages Where possible, migrate critical parsing logic to memory-safe languages like Rust or Go.
2. Safe Standard Libraries Replace unbounded C functions (strcpy, sprintf) with boundary-checking equivalents (strncpy, snprintf).
3. Compiler Defenses Ensure software is compiled with modern defensive flags: ASLR, DEP/NX, Stack Canaries (SSP), and Position Independent Executables (PIE).
Vulnerability Signature
// Vulnerable C Function
void parse_network_packet(char *untrusted_data) \{
char local_buffer[128];
// VULNERABLE: strcpy does not verify the length of the source data
strcpy(local_buffer, untrusted_data);
printf("Packet Processed.");
\}
// EXPLOIT PAYLOAD: 128 bytes of padding + [Overwrite EIP Address]
References and Sources
Vulnerability Code Signature
Attack Data Flow
| Stage | Detail |
|---|---|
| Source | Network packet or file input |
| Vector | Data exceeds the allocated buffer bounds during a copy operation |
| Sink | strcpy(), memcpy(), or pointer arithmetic |
| Impact | Memory corruption, Remote Code Execution (RCE) |
Vulnerable Code Pattern
// ❌ VULNERABLE: Memory Corruption
void process_data(char *input) {
char buffer[128];
// Taint sink: copies without bounds checking
strcpy(buffer, input);
}
Secure Code Pattern
// ✅ SECURE: Bounded Memory Operations
void process_data(char *input) {
char buffer[128];
// Sanitized boundary check
strncpy(buffer, input, sizeof(buffer) - 1);
buffer[sizeof(buffer) - 1] = '\0';
}
How Precogs Detects This
Precogs Binary SAST engine explicitly uncovers memory boundary violations and unsafe memory management functions in compiled binaries.\n