Sign in Sign up
JA · EN · FR
SecPulse
Categories
CVE-2026-42768 low CVSS 3.7

Vulnerability in Openssl (CVE-2026-42768)

Summary

Vulnerability in Openssl (CVE-2026-42768). Risk of unauthorized operations or information disclosure.

Original description

The description as published by the source.

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.

  1. 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…

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-2026-42768 has been found in Openssl.
Risk of unauthorized operations or information disclosure. CVSS score: 3.7/10.
What to do: apply the vendor's official patched release.
If unsure, ask your IT team or search "Openssl CVE-2026-42768" on the vendor's site.

CVE-2026-42768 (Openssl) — CWE-514 / CVSS v3 3.7
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-514) exists in Openssl.

📍 Affected scope

Check the vendor advisory for the affected versions of Openssl.

🔥 Severity

Severity: Low (CVSS 3.7/10). Risk of unauthorized operations or information disclosure.

🔧 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

We use cookies for analytics and ad measurement. This setting applies to all Game co., Ltd. sites. Details