Vulnerability in curl (UBUNTU-CVE-2026-9547)

Summary

Vulnerability in curl (UBUNTU-CVE-2026-9547). Confidential information can be exposed externally. Exploitable via CURLOPT_SSH_KEYFUNCTION. Mitigation: upgrade to 7.81.0-1ubuntu1.25 or later.

Original description

The description as published by the source.

When a libcurl-based application performs transfers via SCP:// or SFTP:// and utilizes the CURLOPT_SSH_KEYFUNCTION callback, it may silently accept an untrusted server. This vulnerability occurs when a server presents a host key type that does not match the specific key type already recorded for that host in the known_hosts file. Instead of rejecting the mismatch, the callback mechanism fails to properly enforce the restriction, allowing the connection to succeed without warning and risking a potential man-in-the-middle attack.

Source: OSV.dev (Open Source Vulnerabilities) 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 UBUNTU-CVE-2026-9547 has been found in curl.
Attackers can target a specific entry point like CURLOPT_SSH_KEYFUNCTION over the network to misuse the product.
Confidential information can be exposed externally.
What to do: upgrade curl to 7.81.0-1ubuntu1.25 or later.
If unsure, ask your IT team or search "curl UBUNTU-CVE-2026-9547" on the vendor's site.

UBUNTU-CVE-2026-9547 (curl)
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Attack surface: CURLOPT_SSH_KEYFUNCTION / known_hosts
Patched: 7.81.0-1ubuntu1.25 — apply immediately
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) exists in curl. Attackers reach the vulnerable code path via CURLOPT_SSH_KEYFUNCTION without authentication.

📍 Affected scope

Check the vendor advisory for the affected versions of curl. Attack surface: CURLOPT_SSH_KEYFUNCTION / known_hosts.

🔥 Severity

Severity: ?. Confidential information can be exposed externally.

🔧 How to fix

Update to 7.81.0-1ubuntu1.25.

🛡️ 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 'curl' . 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 'curl' . | 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 curl 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 patch patch
```
Upgrade curl to 7.81.0-1ubuntu1.25
```
ステージング環境で 7.81.0-1ubuntu1.25 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。
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。

Affected packages

Ubuntu:22.04:LTS curl

[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"7.81.0-1ubuntu1.25"}]}]

Ubuntu:24.04:LTS curl

[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"8.5.0-2ubuntu10.10"}]}]

Ubuntu:25.10 curl

[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"8.14.1-2ubuntu1.4"}]}]

Ubuntu:26.04:LTS curl

[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"8.18.0-1ubuntu2.2"}]}]

References

advisory ubuntu.com
report ubuntu.com
report cve.org
report curl.se