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No exploitation reportedFix available

CVE-2026-34182

CMS AuthEnvelopedData Processing May Accept Forged Messages

No exploitation reported by the sources we read.

  • Published2026-06-09
  • Fixed in3.6.3 · 3.5.7 · 3.4.6 · 3.0.21
  • WeaknessCWE-354

Am I affected?

With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.

Description

Issue Summary: Cryptographic Message Services (CMS) processing fails to perform sufficient input validation on the cipher and tag length fields of AuthEnvelopedData containers, leading to various potential compromises. Impact Summary: Attackers making use of these vulnerabilities may achieve key-equivalent functionality for a given CMS recipient and/or bypass integrity validation for a given message. In one use case, an attacker may send a CMS message containing AuthEnvelopedData with the cipher specified as a non-AEAD cipher. OpenSSL erroneously allows this selection, and attempts to decrypt and validate the message. An on-path attacker who captures one legitimate AES-GCM AuthEnvelopedData addressed to the victim can re-emit it with the recipientInfos set left byte-for-byte intact, so the victim's private key still unwraps the genuine CEK (the content-encryption key), but with the inner OID rewritten to AES-256-OFB (Output Feedback Mode, an unauthenticated keystream mode) and with an attacker-chosen IV and ciphertext. The victim initializes AES-256-OFB under the real CEK, never consults the MAC field, and CMS_decrypt() returns success. If the application under attack responds to the attacker with any indicator showing success or failure of the decryption effort, it is possible for the attacker to use this as an oracle to obtain key equivalent functionality for the CEK used for the chosen recipient of the message. In another use case, an attacker can reduce the tag length of the chosen AEAD cipher for a given AuthEnvelopedData container to be a single byte long, allowing an attacker to brute force CMS decryption, producing an integrity bypass for applications that trust CMS_decrypt() to reject modified content. The FIPS modules are not affected by this issue.

Timeline

dates in UTC
  1. 2026-06-0917:17CVE publishedNVD

Observed activity

isMalicious corpus · updated 2026-10-23 21:37 UTC
Indicators tagged with this CVE, per day0 indicators over 7 days
Block these indicators
  • Firewall list (EDL, text): https://api.ismalicious.com/edl/cve/CVE-2026-34182?format=txt
  • CSV export: https://api.ismalicious.com/edl/cve/CVE-2026-34182?format=csv
  • TAXII collection of exploited CVEs
  • The EDL and CSV take an API key on the Pro plan.

Versions per branch

NVD
OpenSSL
BranchAffectedFixed in
3.6≥ 3.6.0, < 3.6.33.6.3
3.5≥ 3.5.0, < 3.5.73.5.7
3.4≥ 3.4.0, < 3.4.63.4.6
3.0≥ 3.0.0, < 3.0.213.0.21
4.0= 4.0.0no fix published

as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.

Distribution builds and vendor advisories

Packages from OSV.dev and products from the vendors' CSAF advisories.

version not verifiedVersions not verified: read as OSV.dev and the vendors publish them, not checked against each vendor's release list.

Packages

  • opensslAlmaLinux:10all versions · fixed in 1:3.5.5-4.el10_2.alma.1and 3 other packages
  • opensslAlmaLinux:9all versions · fixed in 1:3.5.5-4.el9_8and 3 other packages

Vendor advisories

  • CVE-2026-34182 Red Hat Product Security353 products fixed · 2 known affected

    openssl: CMS AuthEnvelopedData Processing May Accept Forged Messages

    openshift/ose-rhel-coreos-8 as a component of Red Hat OpenShift Container Platform 4 · openshift/ose-rhel-coreos-9 as a component of Red Hat OpenShift Container Platform 4

  • RHSA-2026:84573 Red Hat Product Security40 products fixed

    Red Hat Security Advisory: openssl security update

  • RHSA-2026:84572 Red Hat Product Security30 products fixed

    Red Hat Security Advisory: openssl security update

  • RHSA-2026:83617 Red Hat Product Security39 products fixed

    Red Hat Security Advisory: openssl security update

  • RHSA-2026:82888 Red Hat Product Security1 product fixed

    Red Hat Security Advisory: cert-manager Operator for Red Hat OpenShift 1.17.2

  • RHSA-2026:82857 Red Hat Product Security1 product fixed

    Red Hat Security Advisory: cert-manager Operator for Red Hat OpenShift 1.18.2

22 more advisories

Full record on NVD

Fix

  1. Update OpenSSL to 3.6.3 · 3.5.7 · 3.4.6 · 3.0.21
  2. Vendor fix Red Hat Product Security RHSA-2026:84573 · 40 productsFor details on how to apply this update, which includes the changes described in this advisory, refer to: https://access.redhat.com/articles/11258
  3. Vendor fix Red Hat Product Security RHSA-2026:82888 · 1 productBefore applying this update, make sure all previously released errata relevant to your system have been applied. The steps to apply the upgraded images are different depending on the installation plan approval policy you used when installing the cert-manager Operator for Red Hat OpenShift. - If t…
  4. Vendor fix Red Hat Product Security RHSA-2026:67551 · 3 productsFor details on how to apply this update, which includes the changes described in this advisory, refer to: https://images.redhat.com/
  5. Vendor fix Red Hat Product Security RHSA-2026:58981 · 3 productsPlease consult the RHUI Technology Preview Release Notes at https://access.redhat.com/articles/7141172 for instructions on how to use this image set.
  6. Workaround from the vendor Red Hat Product Security RHSA-2026:84573 · 49 productsSystems configured to operate in FIPS mode are not affected by this vulnerability. To mitigate this issue, ensure that OpenSSL is operating in FIPS mode by enabling the system-wide FIPS policy. This may have broader implications for cryptographic operations on the system and should be evaluated for…

Advisories and patches

Detection

Nuclei template
none so far
ProjectDiscovery
Exploit-DB
no entry
Exploit-DB
Proof-of-concept repositories
none listed
PoC-in-GitHub

Sources

Technical details

CVSS v3 Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
Published
2026-06-09
Last Modified
2026-07-23
NVD status
Analyzed
MSRC Title
CMS AuthEnvelopedData Processing May Accept Forged Messages

Frequently asked questions

What is CVE-2026-34182?

Issue Summary: Cryptographic Message Services (CMS) processing fails to perform sufficient input validation on the cipher and tag length fields of AuthEnvelopedData containers, leading to various potential compromises. Impact Summary: Attackers making use of these vulnerabilities may achieve key-equivalent functionality for a given CMS recipient and/or bypass integrity validation for a given message. In one use case, an attacker may send a CMS message containing AuthEnvelopedData with the cipher specified as a non-AEAD cipher. OpenSSL erroneously allows this selection, and attempts to decrypt and validate the message. An on-path attacker who captures one legitimate AES-GCM AuthEnvelopedData addressed to the victim can re-emit it with the recipientInfos set left byte-for-byte intact, so the victim's private key still unwraps the genuine CEK (the content-encryption key), but with the inner OID rewritten to AES-256-OFB (Output Feedback Mode, an unauthenticated keystream mode) and with an attacker-chosen IV and ciphertext. The victim initializes AES-256-OFB under the real CEK, never consults the MAC field, and CMS_decrypt() returns success. If the application under attack responds to the attacker with any indicator showing success or failure of the decryption effort, it is possible for the attacker to use this as an oracle to obtain key equivalent functionality for the CEK used for the chosen recipient of the message. In another use case, an attacker can reduce the tag length of the chosen AEAD cipher for a given AuthEnvelopedData container to be a single byte long, allowing an attacker to brute force CMS decryption, producing an integrity bypass for applications that trust CMS_decrypt() to reject modified content. The FIPS modules are not affected by this issue.

Is CVE-2026-34182 actively exploited?

Active exploitation of CVE-2026-34182 has not been confirmed. Its EPSS score was 1.1% on 2026-10-22, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2026-34182?

CVE-2026-34182 has a CVSS v3 base score of 9.1 (CRITICAL severity), with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N.

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