Cyber Resilience

CVE-2026-6291

Medium

Published: 25 June 2026

Published
25 June 2026
Modified
26 June 2026
KEV Added
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Patch
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CVSS Score v4 6.0 CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:H/VI:N/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:X
EPSS Score 0.0015 4.8th percentile
Risk Priority 35 floored blend · peak EPSS

Summary

CVE-2026-6291 is a medium-severity Observable Timing Discrepancy (CWE-208) vulnerability in Wolfssl Wolfssl. Its CVSS base score is 6.0 (Medium).

Operationally, ranked at the 4.8th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.

EU & UK References

Vulnerability details

Bleichenbacher padding oracle in PKCS#7 KTRI decryption. When decrypting PKCS#7 EnvelopedData using RSA PKCS#1 v1.5 key transport, wolfSSL returned distinguishable error codes depending on whether RSA padding validation failed versus whether the decrypted content was malformed. An attacker able to…

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submit crafted EnvelopedData messages and observe error responses could use this as a padding oracle to incrementally recover the encrypted Content Encryption Key (CEK). The fix generates a deterministic pseudo-random fake CEK on padding failure (via HMAC-SHA256) and proceeds with decryption identically, using constant-time operations throughout, so that all failure paths produce the same error regardless of padding validity.

CWE(s)
CWE-208

Related Threats

MITRE ATT&CK Enterprise TechniquesAI

Insufficient information to map techniques.
Confidence: LOW · MITRE ATT&CK Enterprise v19.0

CVEs Like This One

CVE-2025-7396Same product: Wolfssl Wolfssl
CVE-2024-1544Same product: Wolfssl Wolfssl
CVE-2026-6331Same product: Wolfssl Wolfssl
CVE-2026-6450Same product: Wolfssl Wolfssl
CVE-2026-5503Same product: Wolfssl Wolfssl
CVE-2021-3336Same product: Wolfssl Wolfssl
CVE-2026-55960Same product: Wolfssl Wolfssl
CVE-2025-7394Same product: Wolfssl Wolfssl
CVE-2026-7532Same product: Wolfssl Wolfssl
CVE-2022-34293Same product: Wolfssl Wolfssl

Affected Assets

wolfssl
wolfssl
3.9.10 — 5.9.2

Mitigating Controls

Likely Mitigating Controls AI

Per-CVE control mapping for this CVE has not run yet; the list below is derived from the weakness types (CWEs) cited in the NVD entry.

SC-30 Concealment and Misdirection
addresses: CWE-208

Timing randomization or delays can mask true operation timing and mislead timing-based attacks.

SC-31 Covert Channel Analysis
addresses: CWE-208

Observable timing discrepancies are a primary mechanism for constructing covert timing channels; analysis identifies and bounds them, limiting exploitation.

References