DEBIAN-CVE-2026-42768
Issue summary: The CMS_decrypt and PKCS7_decrypt functions are vulnerable to Bleichenbacher-style attack when an attacker is able to provide the CMS or S/MIME messages and observe the error code and/or decryption output. Impact summary: The Bleichenbacher-style attack allows an attacker to use the victim's vulnerable application as a way to decrypt or sign messages with the victim's private RSA key. The attack is possible in 2 variants. 1. The decryption API (CMS_decrypt(), PKCS7_decrypt()) is used without providing the recipient certificate. In this case OpenSSL iterates over every KeyTransRecipientInfo (KTRI) without stopping at the first success. An attacker who authors a message with two KTRI entries — the first one wrapping a real CEK under the victim's public key, the second with an arbitrary probe ciphertext — obtains opportunity to iterate the 2nd KTRI to get a valid PKCS#1 v1.5 padding if the error code of the application is available. That is a Bleichenbacher oracle (Bleichenbacher, CRYPTO '98): an adaptive-chosen-ciphertext side channel from which the attacker decrypts any RSA ciphertext to the victim's key or forges any PKCS#1 v1.5 signature under it. 2. When the decryption API (CMS_decrypt(), PKCS7_decrypt()) is provided with the recipient certificate, and the recipient is not found, a random key is substituted. An attacker who authors a message and is able to compare both error code and the result of the decryption, can mount a Bleichenbacher oracle. We are not
DEBIAN-CVE-2026-42768
Primary source · Revision 1
Imported from structured advisory data. Source references identify upstream records or fields; verify affected versions and your deployed configuration.
Security context
Source reference: osv:DEBIAN-CVE-2026-42768
openssl
Source reference: /affected/0/package/name
- Affected versions
- 3.5.1-1
Source reference:
/affected/0/versions3.5.1-1+deb13u1Source reference:
/affected/0/versions3.5.2-1Source reference:
/affected/0/versions3.5.3-1Source reference:
/affected/0/versions3.5.4-1Source reference:
/affected/0/versions3.5.4-1~deb13u1Source reference:
/affected/0/versions3.5.4-1~deb13u2Source reference:
/affected/0/versions3.5.5-1Source reference:
/affected/0/versions3.5.5-1~deb13u1Source reference:
/affected/0/versions3.5.5-1~deb13u2Source reference:
/affected/0/versions3.5.6-1~deb13u1Source reference:
/affected/0/versions - Fixed versions
- 3.5.6-1~deb13u2
Source reference:
/affected/0/ranges - Prerequisites
- Not stated in this record
openssl
Source reference: /affected/1/package/name
- Affected versions
- 3.5.1-1
Source reference:
/affected/1/versions3.5.2-1Source reference:
/affected/1/versions3.5.3-1Source reference:
/affected/1/versions3.5.4-1Source reference:
/affected/1/versions3.5.4-1~deb13u1Source reference:
/affected/1/versions3.5.4-1~deb13u2Source reference:
/affected/1/versions3.5.5-1Source reference:
/affected/1/versions3.5.5-1~deb13u1Source reference:
/affected/1/versions3.5.5-1~deb13u2Source reference:
/affected/1/versions3.5.6-1~deb13u1Source reference:
/affected/1/versions3.5.6-1~deb13u2Source reference:
/affected/1/versions3.5.7-1~deb13u1Source reference:
/affected/1/versions3.5.7-1~deb13u2Source reference:
/affected/1/versions3.5.7-1~deb13u3Source reference:
/affected/1/versions3.6.0-1Source reference:
/affected/1/versions3.6.0-2Source reference:
/affected/1/versions3.6.0~~alpha1-1Source reference:
/affected/1/versions3.6.0~~beta1-1Source reference:
/affected/1/versions3.6.1-1Source reference:
/affected/1/versions3.6.1-2Source reference:
/affected/1/versions3.6.1-3Source reference:
/affected/1/versions3.6.2-1Source reference:
/affected/1/versions - Fixed versions
- 3.6.3-1
Source reference:
/affected/1/ranges - Prerequisites
- Not stated in this record
Structured affected-version data
Original package identities and version rules from this source.
[
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "0"
},
{
"fixed": "3.5.6-1~deb13u2"
}
]
}
],
"package": {
"name": "openssl",
"purl": "pkg:deb/debian/openssl?arch=source&distro=trixie",
"ecosystem": "Debian:13"
},
"versions": [
"3.5.1-1",
"3.5.1-1+deb13u1",
"3.5.2-1",
"3.5.3-1",
"3.5.4-1",
"3.5.4-1~deb13u1",
"3.5.4-1~deb13u2",
"3.5.5-1",
"3.5.5-1~deb13u1",
"3.5.5-1~deb13u2",
"3.5.6-1~deb13u1"
],
"database_specific": {
"source": "https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2026-42768.json"
},
"ecosystem_specific": {
"urgency": "not yet assigned"
}
},
{
"ranges": [
{
"type": "ECOSYSTEM",
"events": [
{
"introduced": "0"
},
{
"fixed": "3.6.3-1"
}
]
}
],
"package": {
"name": "openssl",
"purl": "pkg:deb/debian/openssl?arch=source&distro=forky",
"ecosystem": "Debian:14"
},
"versions": [
"3.5.1-1",
"3.5.2-1",
"3.5.3-1",
"3.5.4-1",
"3.5.4-1~deb13u1",
"3.5.4-1~deb13u2",
"3.5.5-1",
"3.5.5-1~deb13u1",
"3.5.5-1~deb13u2",
"3.5.6-1~deb13u1",
"3.5.6-1~deb13u2",
"3.5.7-1~deb13u1",
"3.5.7-1~deb13u2",
"3.5.7-1~deb13u3",
"3.6.0-1",
"3.6.0-2",
"3.6.0~~alpha1-1",
"3.6.0~~beta1-1",
"3.6.1-1",
"3.6.1-2",
"3.6.1-3",
"3.6.2-1"
],
"database_specific": {
"source": "https://storage.googleapis.com/debian-osv/debian-cve-osv/DEBIAN-CVE-2026-42768.json"
},
"ecosystem_specific": {
"urgency": "not yet assigned"
}
}
]Publisher severity
No explicit severity was provided.
- Event
- #57649 · Revision 1
- Added to Heist Feed
- Publisher date