CVE-2026-5477 | wolfSSL up to 5.9.0 Message wc_CmacUpdate integer overflow (EUVD-2026-21305)

VDB-356797 · CVE-2026-5477 · EUVD-2026-21305 WOLFSSL UP TO 5.9.0 MESSAGE WC_CMACUPDATE INTEGER OVERFLOW HISTORYDIFFRELATEJSONXMLCTI CVSS Meta Temp Score Current Exploit Price (≈) CTI Interest Score 7.3 $0-$5k 2.22+ Summaryinfo A vulnerability was found in wolfSSL up to 5.9.0. It has been rated as critical. Affected by this issue is the function wc_CmacUpdate of the component Message Handler. This manipulation causes integer overflow. This vulnerability is tracked as CVE-2026-5477. The attack is possible to be carried out remotely. No exploit exists. Detailsinfo A vulnerability classified as critical was found in wolfSSL up to 5.9.0. Affected by this vulnerability is the function wc_CmacUpdate of the component Message Handler. The manipulation with an unknown input leads to a integer overflow vulnerability. The CWE definition for the vulnerability is CWE-190. The product performs a calculation that can produce an integer overflow or wraparound, when the logic assumes that the resulting value will always be larger than the original value. This can introduce other weaknesses when the calculation is used for resource management or execution control. As an impact it is known to affect confidentiality, integrity, and availability. The summary by CVE is: An integer overflow existed in the wolfCrypt CMAC implementation, that could be exploited to forge CMAC tags. The function wc_CmacUpdate used the guard `if (cmac->totalSz != 0)` to skip XOR-chaining on the first block (where digest is all-zeros and the XOR is a no-op). However, totalSz is word32 and wraps to zero after 2^28 block flushes (4 GiB), causing the guard to erroneously discard the live CBC-MAC chain state. Any two messages sharing a common suffix beyond the 4 GiB mark then produce identical CMAC tags, enabling a zero-work prefix-substitution forgery. The fix removes the guard, making the XOR unconditional; the no-op property on the first block is preserved because digest is zero-initialized by wc_InitCmac_ex. The weakness was disclosed by Calif.io. The advisory is shared at github.com. This vulnerability is known as CVE-2026-5477 since 04/03/2026. The exploitation appears to be easy. The attack can be launched remotely. The exploitation doesn't need any form of authentication. Technical details are known, but no exploit is available. The price for an exploit might be around USD $0-$5k at the moment (estimation calculated on 04/10/2026). There is no information about possible countermeasures known. It may be suggested to replace the affected object with an alternative product. The vulnerability is also documented in the vulnerability database at EUVD (EUVD-2026-21305). Productinfo Name wolfSSL Version 5.0 5.1 5.2 5.3 5.4 5.5 5.6 5.7 5.8 5.9.0 License open-source Website Product: https://github.com/wolfSSL/wolfssl/ CPE 2.3info 🔒 🔒 🔒 CPE 2.2info 🔒 🔒 🔒 CVSSv4info VulDB Vector: 🔒 VulDB Reliability: 🔍 CNA CVSS-B Score: 🔒 CNA CVSS-BT Score: 🔒 CNA Vector: 🔒 CVSSv3info VulDB Meta Base Score: 7.3 VulDB Meta Temp Score: 7.3 VulDB Base Score: 7.3 VulDB Temp Score: 7.3 VulDB Vector: 🔒 VulDB Reliability: 🔍 CVSSv2info Vector Complexity Authentication Confidentiality Integrity Availability Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock VulDB Base Score: 🔒 VulDB Temp Score: 🔒 VulDB Reliability: 🔍 Exploitinginfo Class: Integer overflow CWE: CWE-190 / CWE-189 CAPEC: 🔒 ATT&CK: 🔒 Physical: No Local: No Remote: Yes Availability: 🔒 Status: Not defined Price Prediction: 🔍 Current Price Estimation: 🔒 0-Day Unlock Unlock Unlock Unlock Today Unlock Unlock Unlock Unlock Threat Intelligenceinfo Interest: 🔍 Active Actors: 🔍 Active APT Groups: 🔍 Countermeasuresinfo Recommended: no mitigation known Status: 🔍 0-Day Time: 🔒 Timelineinfo 04/03/2026 CVE reserved 04/10/2026 +7 days Advisory disclosed 04/10/2026 +0 days VulDB entry created 04/10/2026 +0 days VulDB entry last update Sourcesinfo Product: github.com Advisory: github.com Researcher: Calif.io Status: Confirmed CVE: CVE-2026-5477 (🔒) GCVE (CVE): GCVE-0-2026-5477 GCVE (VulDB): GCVE-100-356797 EUVD: 🔒 Entryinfo Created: 04/10/2026 07:56 Updated: 04/10/2026 08:52 Changes: 04/10/2026 07:56 (65), 04/10/2026 08:52 (1) Complete: 🔍 Cache ID: 99:39C:101 Discussion No comments yet. Languages: en. Please log in to comment. ◂ PreviousOverviewNext ▸