Vulnerability in hpack (CVE-2026-59980)
Summary
Vulnerability in hpack (CVE-2026-59980). Risk of unauthorized operations or information disclosure. Mitigation: upgrade to 4.2.0 or later.
Original description
The description as published by the source.
Impact
Users of the python-hyper/hpack library, most commonly used as downstream dependency of the python-hyper/h2 library (an HTTP/2 client and server implementation). Unbounded variable integer decoding can cause run-away computation on malformed input leading to O(n^2) runtime, effectively blocking further processing with large enough unsanitized input.
Patches
A fix is available in python-hyper/hpack v4.2.0 to restricted variable integer decoding to uint32 to prevent run-away computation.
Workarounds
Sanitize input to hpack decoder for long sequences of 0xFF values to prevent malicious use.
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-2026-59980 has been found in hpack.
Risk of unauthorized operations or information disclosure.
What to do: upgrade hpack to 4.2.0 or later.
If unsure, ask your IT team or search "hpack CVE-2026-59980" on the vendor's site.
CVE-2026-59980 (hpack) — CWE-400
Patched: 4.2.0 — apply immediately
Workaround: Sanitize input to hpack decoder for long sequences of 0xFF values to prevent malicious use.
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.
A vulnerability (CWE-400) exists in hpack.
Check the vendor advisory for the affected versions of hpack.
Severity: ?. Risk of unauthorized operations or information disclosure.
Update to 4.2.0.
Workaround: Sanitize input to hpack decoder for long sequences of 0xFF values to prevent malicious use.
Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Run grep -r 'hpack' . 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 'hpack' . | 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
hpackを grep し、稼働しているサービス・バージョンを把握する。 -
2Apply temporary workaround mitigate
Sanitize input to hpack decoder for long sequences of `0xFF` values to prevent malicious use.パッチが適用されるまでの応急処置として、Sanitize input to hpack decoder for long sequences of
0xFFvalues to prevent malicious use. を実施。回避策の副作用 (機能低下) を確認した上で。 -
3Apply patch patch
Upgrade hpack to 4.2.0ステージング環境で 4.2.0 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。
-
4Post-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
Fix status by distribution
Fixed packages published by each distribution for this CVE
- Debian DEBIAN-CVE-2026-59980 python-hpack
- Ubuntu UBUNTU-CVE-2026-59980 python-hpack
References
- advisory nvd.nist.gov
- advisory github.com
- package github.com
- package pypi.org
- web cs.opensource.google
- web docs.rs
- web github.com
- web github.com
- web github.com