CryptoLib, Heap Buffer Overflow, CVE-2025-30356 (Critical)

How the CVE Works

CVE-2025-30356 is a critical heap buffer overflow vulnerability in CryptoLib versions 1.3.3 and earlier, used in the CCSDS Space Data Link Security Protocol (SDLS-EP). The flaw exists in the `Crypto_TC_ApplySecurity` function due to insufficient validation of the `fl` (frame length) field. While CVE-2025-29912 patched an underflow issue, the fix did not fully prevent unsafe calculations. An attacker can craft malicious frames with manipulated `fl` values, causing `tf_payload_len` to become negative. When interpreted as an unsigned integer, this triggers an oversized memory copy (memcpy), leading to heap corruption, potential remote code execution, or system crashes.

DailyCVE Form

Platform: CryptoLib
Version: ≤1.3.3
Vulnerability: Heap Buffer Overflow
Severity: Critical
Date: 04/29/2025

What Undercode Say:

Exploitation:

Craft a malicious SDLS-EP frame with a manipulated `fl` field.
Force `tf_payload_len` to a negative value, which becomes a large unsigned value.
Trigger heap overflow via memcpy, corrupting adjacent memory.

Detection & Exploit Code:

// Proof-of-Concept (PoC) Snippet
void exploit_sdls_ep() {
uint8_t malicious_frame[bash];
memset(malicious_frame, 0x41, sizeof(malicious_frame));
// Set invalid fl to trigger underflow
malicious_frame[bash] = 0xFF;
send_to_target(malicious_frame);
}

Mitigation:

1. Patch: Upgrade to CryptoLib >1.3.3.

2. Input Validation: Sanitize `fl` field before processing.

Bounds Checking: Ensure `tf_payload_len` is non-negative before memcpy.

Analytics:

Attack Vector: Remote (network-exploitable).
Impact: RCE, DoS, or data leakage.
CVSS 4.0: 9.3 (AV:N/AC:L/PR:N/UI:N/VC:H/VI:H/VA:H).

Protection Commands:

Check CryptoLib version
$ crypto_lib --version
Apply workaround (if patch unavailable)
$ firewall --block-port SDLS_EP_PORT

Debugging:

(gdb) break Crypto_TC_ApplySecurity
(gdb) watch (int)tf_payload_len