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CVE-2026-8720— HMAC-BLAKE2 final discards message when key length exceeds block size

Quick assessment

Affected
wolfSSL wolfSSL
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

wolfSSL是wolfSSL公司开源的一个针对嵌入式系统开发人员使用的小的、可移植的嵌入式SSL编程库。 wolfSSL 5.9.0版本至5.9.1版本存在加密问题漏洞，该漏洞源于wc_Blake2bHmacFinal和wc_Blake2sHmacFinal函数在密钥长度超过块大小时丢弃消息，产生独立于输入的MAC，导致生成的MAC仅依赖于密钥而不依赖于被认证的消息。

AI Predicted 9.8 Difficulty: Easy EPSS 0.16% · P4

Possible ATT&CK Techniques 1 AI

T1557.002 · ARP Cache Poisoning

Affected Version Matrix 1

VendorProduct Version RangeStatus
wolfSSL wolfSSL 5.9.0≤ 5.9.1 affected
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I. Basic Information for CVE-2026-8720

Vulnerability Information
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Vulnerability Title
HMAC-BLAKE2 final discards message when key length exceeds block size
Source: CVE Program / CVE List V5
Vulnerability Description
wc_Blake2bHmacFinal and wc_Blake2sHmacFinal discard the message when the key length exceeds the block size, producing a MAC that is independent of the input. When the supplied key is longer than the BLAKE2 block size the key-hashing branch reinitialized the running hash state, discarding the accumulated message data, so the resulting MAC depended only on the key and not on the message being authenticated. This bug is specific to the HMAC-BLAKE2 APIs that were added in wolfSSL version 5.9.0.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:4.0/AV:L/AC:L/AT:P/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N
Source: CVE Program / CVE List V5
Vulnerability Type
完整性检查值验证不恰当
Source: CVE Program / CVE List V5
Vulnerability Title
wolfSSL 加密问题漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
wolfSSL是wolfSSL公司开源的一个针对嵌入式系统开发人员使用的小的、可移植的嵌入式SSL编程库。 wolfSSL 5.9.0版本至5.9.1版本存在加密问题漏洞，该漏洞源于wc_Blake2bHmacFinal和wc_Blake2sHmacFinal函数在密钥长度超过块大小时丢弃消息，产生独立于输入的MAC，导致生成的MAC仅依赖于密钥而不依赖于被认证的消息。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
wolfSSL wolfSSL 5.9.0 ~ 5.9.1 -

II. Public POCs for CVE-2026-8720

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III. Intelligence Information for CVE-2026-8720

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Patches & Fixes for CVE-2026-8720 (1)

Vendor Pages for CVE-2026-8720 (1)

Same Patch Batch · wolfSSL · 2026-06-25 · 32 CVEs total

CVE-2026-6679 DTLS 1.3 ACK serialization heap buffer overflow via integer truncation
CVE-2026-55958 Renesas TSIP TLS 1.3 transcript buffer out-of-bounds write in tsip_StoreMessage
CVE-2026-55960 Un-negotiated Raw Public Key (RFC 7250) accepted in place of X.509, bypassing chain valida
CVE-2026-55967 AES-GCM streaming APIs do not reject >64 GiB cumulative single messages, enabling counter
CVE-2026-55961 wolfSSL_PKCS7_verify() reports success for degenerate (certs-only) PKCS#7 with no signer
CVE-2026-55962 TLS 1.3 post-handshake authentication: server accepts Finished without client Certificate/
CVE-2026-55964 Chain intermediate CA:TRUE without keyCertSign accepted as a signing CA (temporary CA exem
CVE-2026-12340 Out-of-bounds heap read in SM2/SM3 certificate Subject Key Identifier computation
CVE-2026-10512 X25519 x86_64 assembly final reduction leaves non-canonical field element
CVE-2026-10097 ML-KEM-1024 x64 AVX2 incomplete cipher text comparison enables IND-CCA2 break and static p
CVE-2026-10098 OCSP CertID serial-number length-confusion in wolfSSL_OCSP_resp_find_status
CVE-2026-10592 Wildcard DNS SAN bypasses CA name-constraint checks
CVE-2026-11310 X.509 trust-chain bypass in wolfSSL_X509_verify_cert() via untrusted intermediate anchorin
CVE-2026-11703 Missing SNI/ALPN binding on stateful (session-ID) TLS session resumption
CVE-2026-11999 X.509 trust-chain bypass via path-depth exhaustion in wolfSSL_X509_verify_cert()
CVE-2026-6329 PKCS#12 MAC verification uses attacker-controlled comparison length
CVE-2026-7532 iPAddress name constraints not enforced when WOLFSSL_IP_ALT_NAME is undefined
CVE-2026-6094 Heap buffer overread in wc_PKCS7_DecodeEnvelopedData parsing crafted PKCS7 EnvelopedData
CVE-2026-6731 X.509 name constraint bypass via Subject CN treated as a DNS name
CVE-2026-6325 Out-of-bounds write in SetSuitesHashSigAlgo on oversized signature algorithms list

Showing top 20 of 32 CVEs. View all on vendor page → →

IV. Related Vulnerabilities

Same product: wolfSSL
Same vendor: wolfSSL
Same weakness: CWE-354

V. Comments for CVE-2026-8720

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