Vulnerability in github.com/sylabs/singularity (CVE-2020-13845)

Summary

Vulnerability in github.com/sylabs/singularity (CVE-2020-13845). Data can be tampered with by attackers. Exploitable via legacyinsecure. Mitigation: upgrade to 3.6.0 or later.

Original description

The description as published by the source.

Impact

The Singularity Execution Control List (ECL) allows system administrators to set up a policy that defines rules about what signature(s) must be (or must not be) present on a SIF container image for it to be permitted to run.

In Singularity 3.x versions below 3.6.0, the following issues allow the ECL to be bypassed by a malicious user:

Image integrity is not validated when an ECL policy is enforced.
The fingerprint required by the ECL is compared against the signature object descriptor(s) in the SIF file, rather than to a cryptographically validated signature. Thus, it is trivial to craft an arbitrary payload which will be permitted to run, even if the attacker does not have access to the private key associated with the fingerprint(s) configured in the ECL.

Patches

These issues are addressed in Singularity 3.6.0.

All users are advised to upgrade to 3.6.0. Note that Singularity 3.6.0 uses a new signature format that is necessarily incompatible with Singularity < 3.6.0 - e.g. Singularity 3.5.3 cannot verify containers signed by 3.6.0.

Version 3.6.0 includes a legacyinsecure option that can be set to legacyinsecure = true in ecl.toml to allow the ECL to perform verification of the older, and insecure, legacy signatures for compatibility with existing containers. This does not guarantee that containers have not been modified since signing, due to other issues in the legacy signature format. The option should be used only to temporarily ease the tr…

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-2020-13845 has been found in github.com/sylabs/singularity.
Attackers can target a specific entry point like legacyinsecure over the network to misuse the product.
Data can be tampered with by attackers.
What to do: upgrade github.com/sylabs/singularity to 3.6.0 or later.
If unsure, ask your IT team or search "github.com/sylabs/singularity CVE-2020-13845" on the vendor's site.

CVE-2020-13845 (github.com/sylabs/singularity) — CWE-347
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Attack surface: legacyinsecure / ecl.toml
Patched: 3.6.0 — apply immediately
Workaround: This issue affects any installation of Singularity configured to use the Execution Control List (ECL) functionality.
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-347) exists in github.com/sylabs/singularity. Attackers reach the vulnerable code path via legacyinsecure without authentication.

📍 Affected scope

Check the vendor advisory for the affected versions of github.com/sylabs/singularity. Attack surface: legacyinsecure / ecl.toml.

🔥 Severity

Severity: ?. Data can be tampered with by attackers.

🔧 How to fix

Update to 3.6.0.

🛡️ Workaround

Workaround: This issue affects any installation of Singularity configured to use the Execution Control List (ECL) functionality.

🔍 Detection

Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Run grep -r 'github.com/sylabs/singularity' . 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
Identify exposure identify
```
grep -r 'github.com/sylabs/singularity' . | 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 github.com/sylabs/singularity を grep し、稼働しているサービス・バージョンを把握する。
2
Apply temporary workaround mitigate
```
This issue affects any installation of Singularity configured to use the Execution Control List (ECL) functionality.
```
パッチが適用されるまでの応急処置として、This issue affects any installation of Singularity configured to use the Execution Control List (ECL) functionality. を実施。回避策の副作用 (機能低下) を確認した上で。
3
Apply patch patch
```
Upgrade github.com/sylabs/singularity to 3.6.0
```
ステージング環境で 3.6.0 に上げて回帰テスト → 本番反映。回帰テストはアプリの主要ハッピーパスを含めること。
4
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。

Affected packages

Go github.com/sylabs/singularity

[{"type":"SEMVER","events":[{"introduced":"3.0.0"},{"fixed":"3.6.0"}]}]

Fix status by distribution

Fixed packages published by each distribution for this CVE

Ubuntu UBUNTU-CVE-2020-13845 singularity-container