CVE-2026-6291 json
Bleichenbacher padding oracle in PKCS#7 KTRI RSA PKCS#1 v1.5 decryption
published 2026-06-25 4 mo ago modified 2026-07-25 3 mo ago also EUVD-2026-39482 , GHSA-hvwm-w7rw-23cv , JLSEC-2026-745
- cvss
- 6.5
- version 3.1, NVD
- cisa kev
- Not listed
- not in CISA's catalog
- epss
- 0.2%
- EPSS 0.2% chance of exploitation in 30 days, percentile 15%
- public exploits
- 0
- none known
Summary
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.
Patch / fix
- julia wolfSSL_jll 5.9.2+0
- wolfssl wolfssl 5.9.2
- wolfssl Alpine 3.24 5.9.2-r0
alpine advisories ALPINE-CVE-2026-6291
Alpine secdb © Alpine Linux, from https://secdb.alpinelinux.org via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0
- github.com/wolfSSL/wolfssl#10203 pull request
CISA SSVC
- Exploitation
- none
- Automatable
- no
- Technical impact
- partial
- Assessed
- 4 mo ago
Exploit prediction
0.24% chance of exploitation in the next 30 days, higher than 15% of all scored CVEs (FIRST EPSS, 2026-11-08).
CVSS scores
| assigned by | version | score | vector |
|---|---|---|---|
| CNA | 4.0 | 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 |
| CNA | 4.0 | 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 |
| NVD | 3.1 | 6.5 | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N |
| OSV | 3.1 | 6.5 | CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N |
Affected packages
| ecosystem | package | affected | fixed in |
|---|---|---|---|
| julia | wolfSSL_jll | <5.9.2+0 |
5.9.2+0 |
Affected products
- wolfSSL wolfSSL
Classification
- Weakness
-
- CWE-208 Observable Timing Discrepancy
References
-
github.com
/wolfSSL/wolfssl/pull/10203
patch, issue-tracking, web
-
wolfssl.com
/docs/security-vulnerabilities/
vendor-advisory, web
-
github.com
/advisories/GHSA-hvwm-w7rw-23cv
web
-
nvd.nist.gov
/vuln/detail/CVE-2026-6291
web
-
wolfssl.com
/docs/security-vulnerabilities
web
Sources
- CVE List CVE-2026-6291
- NVD CVE-2026-6291
- OSV JLSEC-2026-745
Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.