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CVE-2026-5504

PKCS7 CBC Padding Oracle — Plaintext Recovery

6.3 MediumFix available

A padding oracle exists in wolfSSL's PKCS7 CBC decryption that could allow an attacker to recover plaintext through repeated decryption queries with modified ciphertext. In previous versions of wolfSSL the interior padding bytes are not validated.

Attack profile

How easy it is to exploit

Attack vector
Network
Complexity
High
Privileges needed
None
User interaction
None

What an attacker can affect

Confidentiality
Low
Integrity
None
Availability
None

Exploit likelihood

0.11%Up 0.1 points since Apr 10, 2026
90%50%10%1%

What each source reports

CVE List Score used 6.3

PKCS7 CBC Padding Oracle — Plaintext Recovery

A padding oracle exists in wolfSSL's PKCS7 CBC decryption that could allow an attacker to recover plaintext through repeated decryption queries with modified ciphertext. In previous versions of wolfSSL the interior padding bytes are not validated.

Record
CVE-2026-5504
CVSS 4.0
6.3 MediumCVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N
Weakness
CWE-354
Updated
2026-11-02
EUVDEUVD-2026-21235 6.3

A padding oracle exists in wolfSSL's PKCS7 CBC decryption that could allow an attacker to recover plaintext through repeated decryption queries with modified ciphertext. In previous versions of wolfSSL the interior padding bytes are not validated.

Record
EUVD-2026-21235
CVSS 4.0
6.3 MediumCVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N
Updated
2026-11-02
GitHub AdvisoriesGHSA-qvjw-73xm-jw34 6.3

A padding oracle exists in wolfSSL's PKCS7 CBC decryption that could allow an attacker to recover...

A padding oracle exists in wolfSSL's PKCS7 CBC decryption that could allow an attacker to recover plaintext through repeated decryption queries with modified ciphertext. In previous versions of wolfSSL the interior padding bytes are not validated.

Record
GHSA-qvjw-73xm-jw34
CVSS 4.0
6.3 MediumCVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:L/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
CVSS 3.1
5.3 MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
Weakness
CWE-354
Updated
2026-11-02
NVD 6.3

A padding oracle exists in wolfSSL's PKCS7 CBC decryption that could allow an attacker to recover plaintext through repeated decryption queries with modified ciphertext. In previous versions of wolfSSL the interior padding bytes are not validated.

Record
CVE-2026-5504
CVSS 4.0
6.3 MediumCVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:L/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
CVSS 3.1
5.3 MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
Weakness
CWE-354
Updated
2026-11-02
OSVALPINE-CVE-2026-5504 5.3

A padding oracle exists in wolfSSL's PKCS7 CBC decryption that could allow an attacker to recover plaintext through repeated decryption queries with modified ciphertext. In previous versions of wolfSSL the interior padding bytes are not validated.

Record
ALPINE-CVE-2026-5504
CVSS 3.1
5.3 MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
Updated
2026-11-03
OSV 6.3

PKCS7 CBC Padding Oracle — Plaintext Recovery

A padding oracle exists in wolfSSL's PKCS7 CBC decryption that could allow an attacker to recover plaintext through repeated decryption queries with modified ciphertext. In previous versions of wolfSSL the interior padding bytes are not validated.

Record
CVE-2026-5504
CVSS 4.0
6.3 MediumCVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N
Weakness
CWE-354
Updated
2026-11-02
OSVDEBIAN-CVE-2026-5504 5.3

A padding oracle exists in wolfSSL's PKCS7 CBC decryption that could allow an attacker to recover plaintext through repeated decryption queries with modified ciphertext. In previous versions of wolfSSL the interior padding bytes are not validated.

Record
DEBIAN-CVE-2026-5504
CVSS 3.1
5.3 MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
Updated
2026-11-02
OSVJLSEC-2026-732 6.3

A padding oracle exists in wolfSSL's PKCS7 CBC decryption that could allow an attacker to recover...

A padding oracle exists in wolfSSL's PKCS7 CBC decryption that could allow an attacker to recover plaintext through repeated decryption queries with modified ciphertext. In previous versions of wolfSSL the interior padding bytes are not validated.

Record
JLSEC-2026-732
CVSS 4.0
6.3 MediumCVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:L/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
CVSS 3.1
5.3 MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
Updated
2026-11-02
OSVUBUNTU-CVE-2026-5504 6.3

A padding oracle exists in wolfSSL's PKCS7 CBC decryption that could allow an attacker to recover plaintext through repeated decryption queries with modified ciphertext. In previous versions of wolfSSL the interior padding bytes are not validated.

Record
UBUNTU-CVE-2026-5504
CVSS 4.0
6.3 MediumCVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N
CVSS 3.1
5.3 MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N
Updated
2026-11-02

Affected products

Affected packages

Affected packages
PackageAffectedFixed
wolfssl
Alpine:v3.23
 before 5.9.1-r0
5.9.1-r0
wolfssl
Alpine:v3.24
 before 5.9.1-r0
5.9.1-r0
wolfssl
Debian:12
 All versions, plus listed versions
5.5.4-25.5.4-2+deb12u15.5.4-2+deb12u25.5.4-2+deb12u35.5.4-2.1
Show 22 moreShow less
5.6.4-15.6.4-25.6.6-15.6.6-1.15.6.6-1.25.6.6-1.35.6.6-1.3~exp15.7.0-0.15.7.0-0.25.7.0-0.35.7.2-0.15.7.2-0.25.7.2-0.35.7.2-0.45.8.2-15.8.2-1.15.8.2-1.25.8.4-15.9.0-0.15.9.0-0.25.9.1-0.15.9.2-1
 None known
wolfssl
Debian:13
 All versions, plus listed versions
5.7.2-0.15.7.2-0.1+deb13u15.7.2-0.1+deb13u25.7.2-0.25.7.2-0.3
Show 9 moreShow less
5.7.2-0.45.8.2-15.8.2-1.15.8.2-1.25.8.4-15.9.0-0.15.9.0-0.25.9.1-0.15.9.2-1
 None known
wolfSSL_jll
Julia
 before 5.9.2+0
5.9.2+0
wolfssl
Ubuntu:16.04:LTS
 All versions, plus listed versions
3.4.8+dfsg-1
 None known
wolfssl
Ubuntu:18.04:LTS
 All versions, plus listed versions
3.10.2+dfsg-23.12.0+dfsg-13.12.2+dfsg-13.13.0+dfsg-1
 None known
wolfssl
Ubuntu:20.04:LTS
 All versions, plus listed versions
4.1.0+dfsg-24.2.0+dfsg-14.2.0+dfsg-24.2.0+dfsg-34.3.0+dfsg-2
 None known
wolfssl
Ubuntu:22.04:LTS
 All versions, plus listed versions
4.6.0-35.0.0-15.1.1-15.2.0-15.2.0-2
 None known
wolfssl
Ubuntu:24.04:LTS
 All versions, plus listed versions
5.5.4-25.5.4-2.15.6.4-25.6.6-1.25.6.6-1.35.6.6-1.3build1
 None known
wolfssl
Ubuntu:25.10
 All versions, plus listed versions
5.7.2-0.1
 None known
wolfssl
Ubuntu:26.10
 All versions, plus listed versions
5.9.1-0.15.9.2-1
 None known
wolfssl
Ubuntu:26.04:LTS
 All versions, plus listed versions
5.7.2-0.15.8.2-1.25.8.4-15.9.1-0.1
 None known

History

History
RecordedChangedSources
affected, aliases, referencesOSV
first indexedCVE List, EUVD, GitHub Advisories, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2026-5504 is a medium vulnerability (CVSS 6.3) in Wolfssl, published April 9, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.11%, the 1st percentile. Fixed in wolfssl 5.9.1-r0.

References

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