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🛡️ CVE-2026-34182 — openssl

🔴 CVSS 9.1 — Critical ✅ No Known Exploit CWE-354 NVD
9.1
CVSS Score
0 Low4 Medium7 High9 Critical10

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.

How this vulnerability can be exploited

This issue can be reached over the network, attack complexity is low, an attacker needs no 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 high, availability none.

CVSS metrics in full

The score comes from this vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/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: None — an unauthenticated stranger can try it.
  • 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: High — total loss, or loss the attacker controls.
  • Availability impact: None.

Weakness class

CVE-2026-34182 is classified as CWE-354: Improper Validation of Integrity Check Value. A checksum or integrity value is not verified properly, so tampered data passes as intact.

Affected software

CVE-2026-34182 is recorded against 1 package.

  • openssl

Timeline and source

Published on 9 June 2026 and last revised on 23 July 2026. No public exploit is currently recorded for this entry. A vendor advisory or fix has been published. Record sourced from NVD.

References

github.com
github.com
github.com
github.com
github.com
openssl-library.org

Other advisories for this package

openssl 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-354: Improper Validation of Integrity Check Value) in other software:

CVE-2026-34182 on other distributions

Each distribution ships its own build and its own fixed version. Pick the one you run:

Details

Severity CRITICAL
CVSS Score 9.1
CVSS Vector CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
CWE CWE-354
Public Exploit ✅ No
Source NVD
Published 2026-06-09
Updated 2026-08-20
Modified 2026-07-23

Affected Packages

Software From version Fixed in
openssl — —

Exploit Protection

Are you running openssl?

CVE-2026-34182 carries CVSS 9.1 Critical rating. BotEraser checks your installation against this and other known CVE records, and blocks IPs associated with exploit activity.

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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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