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CVE-2026-34182 critical CVSS 9.1

Vulnerability in Openssl (CVE-2026-34182)

Summary

Vulnerability in Openssl (CVE-2026-34182). Confidential information can be exposed externally.

Original description

The description as published by the source.

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 leng…

Source: GitHub Security Advisories (Global) NVD GitHub Advisory

Auto-generated summary

Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.

A vulnerability tracked as CVE-2026-34182 has been found in Openssl.
Confidential information can be exposed externally. CVSS score: 9.1/10.
What to do: apply the vendor's official patched release.
If unsure, ask your IT team or search "Openssl CVE-2026-34182" on the vendor's site.

CVE-2026-34182 (Openssl) — CWE-354 / CVSS v3 9.1
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.

❓ What is the problem

A vulnerability (CWE-354) exists in Openssl.

📍 Affected scope

Check the vendor advisory for the affected versions of Openssl.

🔥 Severity

Severity: Critical (CVSS 9.1/10). Confidential information can be exposed externally.

🔧 How to fix

Update to the patched release per vendor advisory.

🛡️ Workaround

Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.

🔍 Detection

Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Run grep -r 'Openssl' . against your dependency files (package-lock.json, requirements.txt, go.sum) to find affected services.

Response actions

Concrete steps and command examples for SOC/SRE teams to execute in order

  1. 1
    Identify exposure identify 
    grep -r 'Openssl' . | grep -v node_modules

    リポジトリと本番環境の依存ファイル (package-lock.json / requirements.txt / go.sum / Gemfile.lock 等) で Openssl を grep し、稼働しているサービス・バージョンを把握する。

  2. 2
    Post-deployment verification verify 
    Confirm patched version is live in production

    パッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。

Fix status by distribution

Fixed packages published by each distribution for this CVE

References

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