CVE-2026-30910: Iamb Crypt Buffer Overflow Vulnerability

CVE-2026-30910 Overview

CVE-2026-30910 is an Integer Overflow vulnerability affecting Crypt::Sodium::XS versions through 0.001000 for Perl. The vulnerability stems from insufficient size validation in multiple cryptographic functions, which fail to verify that output sizes will remain below SIZE_MAX. This can result in integer wraparound, leading to undersized output buffers that may cause application crashes or, in specific scenarios involving aes256gcm encryption and signature operations, potential buffer overflow conditions.

The affected functions include combined AEAD encryption, combined signature creation, and bin2hex operations. While exploiting this vulnerability requires processing extremely large message payloads, the potential impact ranges from denial of service through application crashes to memory corruption in certain encryption modes.

Critical Impact

Integer overflow in cryptographic operations can lead to buffer underallocation, causing crashes in bin2hex and most encryption algorithms. For aes256gcm encryption and signature operations, undersized buffers could enable buffer overflow attacks.

Affected Products

• Crypt::Sodium::XS versions through 0.001000 for Perl

Discovery Timeline

• 2026-03-08 - CVE CVE-2026-30910 published to NVD
• 2026-03-10 - Last updated in NVD database

Technical Details for CVE-2026-30910

Vulnerability Analysis

The vulnerability exists due to missing integer overflow checks in several critical functions within the Crypt::Sodium::XS Perl module. When processing input data, the affected functions calculate the required output buffer size by adding constant values to the input length. However, these calculations do not validate whether the result exceeds SIZE_MAX, the maximum value representable by the size_t type.

When extremely large input sizes are provided, the addition operation can wrap around, producing a value significantly smaller than the actual required buffer size. This results in memory allocation for an undersized buffer, which is then used to store the cryptographic operation's output.

The specific input size thresholds that trigger the vulnerability vary by function:

• For bin2hex: input size must exceed SIZE_MAX / 2
• For AEGIS encryption: input size must exceed SIZE_MAX - 32U
• For other encryption modes: input size must exceed SIZE_MAX - 16U
• For signatures: input size must exceed SIZE_MAX - 64U

The severity differs based on the affected operation. For bin2hex and most encryption algorithms, the undersized buffer leads to crashes when the operation attempts to write beyond allocated memory. However, for aes256gcm encryption and signature operations, the memory corruption could potentially be exploited for more severe attacks.

Root Cause

The root cause is classified as CWE-190 (Integer Overflow or Wraparound). The affected functions perform arithmetic operations on input size values without bounds checking against SIZE_MAX. When the input length approaches the maximum value of size_t, adding the required overhead bytes causes the calculation to wrap around to a small positive number, resulting in buffer underallocation.

Attack Vector

The attack vector is network-based, requiring an attacker to supply maliciously crafted input to an application using the vulnerable Crypt::Sodium::XS module. Exploitation requires:

1. An application that processes attacker-controlled data through the vulnerable cryptographic functions
2. The ability to provide input of sufficient size to trigger the integer overflow
3. The application must not have independent input size limits that would prevent processing such large payloads

While the theoretical attack requirements (extremely large input sizes approaching SIZE_MAX) make real-world exploitation unlikely on most systems, the vulnerability represents a defense-in-depth failure that could be chained with other attack techniques. The network attack vector with no authentication requirements means any application exposing these functions to network input is potentially at risk, though practical exploitation would require circumstances where such large data transfers are permitted.

Detection Methods for CVE-2026-30910

Indicators of Compromise

• Application crashes in Perl processes utilizing Crypt::Sodium::XS during cryptographic operations
• Unexpected memory allocation failures or segmentation faults in Perl applications performing encryption or signature operations
• Anomalously large data transfers to applications using libsodium bindings

Detection Strategies

• Monitor for Perl application crashes with stack traces referencing Crypt::Sodium::XS functions, particularly bin2hex, AEAD encryption, or signature operations
• Implement application-level logging to detect unusually large input sizes being passed to cryptographic functions
• Deploy runtime application self-protection (RASP) solutions that can detect integer overflow conditions in memory allocation

Monitoring Recommendations

• Audit deployed Perl applications to identify those using Crypt::Sodium::XS versions 0.001000 or earlier
• Monitor system logs for out-of-memory errors or buffer overflow detections in Perl processes
• Implement input size validation at application boundaries to prevent excessively large payloads from reaching cryptographic functions

How to Mitigate CVE-2026-30910

Immediate Actions Required

• Upgrade Crypt::Sodium::XS to version 0.001001 or later, which includes fixes for the integer overflow issues
• Review applications using Crypt::Sodium::XS and implement input size validation to reject excessively large payloads before they reach cryptographic functions
• Consider temporarily disabling affected functionality in critical applications until patching is complete

Patch Information

The vulnerability has been addressed in Crypt::Sodium::XS version 0.001001. The fix adds proper bounds checking to ensure output size calculations do not exceed SIZE_MAX before memory allocation. Detailed changelog information is available in the MetaCPAN Release Changes. Additional technical details about the vulnerability disclosure can be found in the Openwall OSS Security Posting.

Workarounds

• Implement strict input size limits at the application layer to reject payloads that could approach the overflow threshold
• Add validation logic before cryptographic operations to ensure input sizes remain well below SIZE_MAX minus the maximum overhead value (64U for signatures)
• Consider using alternative Perl cryptographic modules that include proper bounds checking until upgrade is possible

# Upgrade Crypt::Sodium::XS via CPAN
cpan install Crypt::Sodium::XS

# Verify installed version
perl -MCrypt::Sodium::XS -e 'print $Crypt::Sodium::XS::VERSION . "\n"'
# Ensure version is 0.001001 or higher