ASN.1 strings are represented internally within OpenSSL as a… (CVE-2021-3712)

Summary

Vulnerability reported (CVE-2021-3712). Confidential information can be exposed externally.

Original description

The description as published by the source.

ASN.1 strings are represented internally within OpenSSL as an ASN1_STRING structure which contains a buffer holding the string data and a field holding the buffer length. This contrasts with normal C strings which are repesented as a buffer for the string data which is terminated with a NUL (0) byte. Although not a strict requirement, ASN.1 strings that are parsed using OpenSSL's own "d2i" functions (and other similar parsing functions) as well as any string whose value has been set with the ASN1_STRING_set() function will additionally NUL terminate the byte array in the ASN1_STRING structure. However, it is possible for applications to directly construct valid ASN1_STRING structures which do not NUL terminate the byte array by directly setting the "data" and "length" fields in the ASN1_STRING array. This can also happen by using the ASN1_STRING_set0() function. Numerous OpenSSL functions that print ASN.1 data have been found to assume that the ASN1_STRING byte array will be NUL terminated, even though this is not guaranteed for strings that have been directly constructed. Where an application requests an ASN.1 structure to be printed, and where that ASN.1 structure contains ASN1_STRINGs that have been directly constructed by the application without NUL terminating the "data" field, then a read buffer overrun can occur. The same thing can also occur during name constraints processing of certificates (for example if a certificate has been directly constructed by the applicatio…

Source: OSV.dev (Open Source Vulnerabilities) NVD GitHub Advisory OSV

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-2021-3712 has been found.
Confidential information can be exposed externally.
What to do: apply the vendor's official patched release.
If unsure, ask your IT team or search "CVE-2021-3712" on the vendor's site.

CVE-2021-3712
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Affected: 1.1.1 - 1.1.1k
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 (unclassified) has been reported.

📍 Affected scope

Affected versions: 1.1.1 - 1.1.1k.

🔥 Severity

Severity: ?. Confidential information can be exposed externally.

🔧 How to fix

Update to the patched release per vendor advisory. (If a vulnerable version 1.1.1 - 1.1.1k is in production, plan an immediate maintenance window.)

🛡️ 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. Audit SBOM/dependencies to find affected services.

Response actions

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

1
Identify exposure identify
```
Audit SBOM/dependencies for affected components.
```
資産台帳・SBOM・依存マニフェストで影響コンポーネントを特定する。
2
Match against affected range verify
```
Confirm if version satisfies `1.1.1 - 1.1.1k`
```
Step 1 で見つかったバージョンが影響範囲 1.1.1 - 1.1.1k に該当するか照合。本番で稼働中ならインシデント扱い。
3
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

Alpine Linux ALPINE-CVE-2021-3712 openssl Fixed in: 1.1.1l-r0
Debian DEBIAN-CVE-2021-3712 openssl Fixed in: 1.1.1l-1
Ubuntu UBUNTU-CVE-2021-3712 openssl Fixed in: 1.0.1f-1ubuntu2.27+esm4

ASN.1 strings are represented internally within OpenSSL as an ASN1_STRING structure which contains a buffer holding the…