Information Disclosure in Haxx (CVE-2026-9545)
Summary
Vulnerability in Haxx (CVE-2026-9545). Confidential information can be exposed externally. Exploitable via CURLOPT_SSL_SESSIONID_CACHE.
Original description
The description as published by the source.
In this scenario, libcurl first uses a proper HTTP/3 server for the initial
transfers, and when it makes a second transfer to the same site it has been
replaced by the attacker's impostor machine - without a valid certificate.
When libcurl returns to the hostname the second time with a cached SSL session
(CURLOPT_SSL_SESSIONID_CACHE is not disabled) and early data enabled (the
CURLSSLOPT_EARLYDATA bit is set in CURLOPT_SSL_OPTIONS), libcurl might
send off the second request's bytes on that new connection before enforcing
the certificate verification failure. Potentially leaking sensitive
information.
Source: NIST National Vulnerability Database 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-2026-9545 has been found in Haxx.
Attackers can target a specific entry point like CURLOPT_SSL_SESSIONID_CACHE over the network to misuse the product.
Confidential information can be exposed externally. CVSS score: 7.5/10.
What to do: apply the vendor's official patched release.
If unsure, ask your IT team or search "Haxx CVE-2026-9545" on the vendor's site.
CVE-2026-9545 (Haxx) — CWE-200 / CVSS v3 7.5
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Attack surface: CURLOPT_SSL_SESSIONID_CACHE / CURLSSLOPT_EARLYDATA / CURLOPT_SSL_OPTIONS
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.
Information disclosure (CWE-200) exists in Haxx. Attackers reach the vulnerable code path via CURLOPT_SSL_SESSIONID_CACHE without authentication.
Check the vendor advisory for the affected versions of Haxx. Attack surface: CURLOPT_SSL_SESSIONID_CACHE / CURLSSLOPT_EARLYDATA / CURLOPT_SSL_OPTIONS.
Severity: High (CVSS 7.5/10). Confidential information can be exposed externally.
Update to the patched release per vendor advisory.
Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.
Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Run grep -r 'Haxx' . 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
-
1Identify exposure identify
grep -r 'Haxx' . | 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
Haxxを grep し、稼働しているサービス・バージョンを把握する。 -
2Post-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-2026-9545 curl Fixed in: 8.22.0-r0
- Ubuntu UBUNTU-CVE-2026-9545 curl Fixed in: 8.14.1-2ubuntu1.4
References
- web curl.se
- web curl.se
- web hackerone.com
- web nvd.nist.gov
- web github.com