Raw vector
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:XCVSS and EPSS are reproduced from their sources (NVD, FIRST EPSS). Risk Priority is our own derived reading, not an NVD score.
Summary
CVE-2026-5477 is a high-severity Integer Overflow or Wraparound (CWE-190) vulnerability in Wolfssl Wolfssl. Its CVSS base score is 8.2 (High).
Operationally, exploitation aligns with the MITRE ATT&CK technique LSA Secrets (T1003.004); ranked at the 27th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.
The strongest mitigations our analysis identified map to SA-11 (Developer Testing and Evaluation) and SA-8 (Security and Privacy Engineering Principles) — see the control section below for these in your framework.
Deeper analysis AI-assisted summary
Synthesised by an AI model from the NVD description and linked references — a reading aid, not an authoritative source.
CVE-2026-5477 is an integer overflow vulnerability (CWE-190) in the wolfCrypt CMAC implementation within the wolfSSL cryptographic library. The issue arises in the wc_CmacUpdate function, which uses a guard condition `if (cmac->totalSz != 0)` to skip XOR-chaining on the first block, where the digest is all-zeros and the operation is a no-op. However, totalSz is a word32 value that wraps around to zero after 2^28 block flushes (equivalent to 4 GiB of data), causing the guard to incorrectly discard the live CBC-MAC chain state.
An unauthenticated remote attacker with network access can exploit this vulnerability due to its CVSS v3.1 score of 7.5 (AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N). By processing two messages that share a common suffix beyond the 4 GiB mark, the attacker can generate identical CMAC tags with zero additional work, enabling a prefix-substitution forgery attack that violates message integrity.
The wolfSSL project has addressed the vulnerability via a pull request at https://github.com/wolfSSL/wolfssl/pull/10102, which removes the problematic guard condition and makes the XOR operation unconditional. This fix preserves the no-op behavior on the first block because the digest is zero-initialized by wc_InitCmac_ex, ensuring proper CBC-MAC chaining without relying on the totalSz check.
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-21305
Vulnerability Data
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…
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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.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise Techniques
CVEs Like This One
Affected Assets
Mitigating Controls
Control response
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V5.2.6
Mitigating Controls (NIST 800-53 r5) AI
Developer testing and evaluation (static analysis, fuzzing, unit tests) directly finds integer overflow defects before deployment.
Secure engineering principles require use of safe arithmetic constructs or language features that structurally eliminate integer overflow during calculation.
Input validation enforces bounds on values before arithmetic, stopping the conditions that trigger overflow or wraparound.
Mitigating Controls (NIST CSF 2.0) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.
Secure SDLC practices directly require use of safe arithmetic, bounds checks, and testing that prevent integer overflows.
Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.