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🛡️ CVE-2026-6291 — wolfssl

🟡 CVSS 6.5 — Medium ✅ No Known Exploit CWE-208 NVD
6.5
CVSS Score
0 Low4 Medium7 High9 Critical10

Description

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 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.

How this vulnerability can be exploited

This issue can be reached over the network, attack complexity is low, an attacker needs low-level privileges on the target. No user interaction is required. The scope is unchanged, so the impact stays within the vulnerable component. Rated impact: confidentiality high, integrity none, availability none.

CVSS metrics in full

The score comes from this vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N

  • Attack vector: Network — reachable from anywhere that can route to the service.
  • Attack complexity: Low — the attack works reliably, with no preparation.
  • Privileges required: Low — an ordinary user account is enough.
  • User interaction: None — nobody has to be tricked into anything.
  • Scope: Unchanged — the damage stays inside the vulnerable component.
  • Confidentiality impact: High — total loss, or loss the attacker controls.
  • Integrity impact: None.
  • Availability impact: None.

Weakness class

CVE-2026-6291 is classified as CWE-208: Observable Timing Discrepancy. Two separate operations in a product require different amounts of time to complete, in a way that is observable to an actor and reveals security-relevant information about the state of the product, such as whether a particular operation was successful or not.

Affected software

CVE-2026-6291 is recorded against 1 package.

  • wolfssl (from 3.9.10 up to 5.9.2)

Timeline and source

Published on 25 June 2026 and last revised on 26 June 2026. No public exploit is currently recorded for this entry. Record sourced from NVD.

References

github.com
www.wolfssl.com

Other advisories for this package

wolfssl has other advisories on record. If you are patching this one, these are worth checking on the same host:

Same weakness in other software

These advisories are the same class of weakness (CWE-208: Observable Timing Discrepancy) in other software:

Details

Severity MEDIUM
CVSS Score 6.5
CVSS Vector CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N
CWE CWE-208
Public Exploit ✅ No
Source NVD
Published 2026-06-25
Updated 2026-08-20
Modified 2026-06-26
Fix URL N/A

Affected Packages

Software From version Fixed in
wolfssl 3.9.10 5.9.2

Similar Threats

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ⓘ Data Notice: The information presented above has been compiled from publicly available internet sources. Boteraser aggregates this data solely for informational purposes and does not independently classify, evaluate, or endorse any findings about the vulnerabilities listed. The accuracy and completeness of this information is the sole responsibility of the original publishers. Boteraser and its operators accept no liability for any decisions made based on this data.

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