Vulnerability in rustls-webpki (CVE-2026-93599)
Summary
Vulnerability in rustls-webpki (CVE-2026-93599). Risk of unauthorized operations or information disclosure. Mitigation: upgrade to 0.103.13 or later.
Original description
The description as published by the source.
rustls-webpki through 0.103.12 (and 0.104.0-alpha releases before 0.104.0-alpha.7) contains a reachable panic in bit_string_flags() in src/der.rs. The input guard fails to reject a named-bit BIT STRING whose content is exactly [0x00] (zero padding bits and no data bytes), so raw_bits.len() - 1 underflows on the empty slice and the subsequent index operation panics (subtract-with-overflow in debug, index-out-of-bounds in release). The condition is reachable through the public API BorrowedCertRevocationList::from_der() when a CRL contains an issuingDistributionPoint extension with such an onlySomeReasons value. Exploitation requires an application that explicitly opts in to CRL revocation checking by passing RevocationOptions to verify_for_usage() and that parses CRL bytes obtained from a source the attacker can influence; the default rustls configuration, which does not use RevocationOptions, is unaffected. A crafted CRL causes a denial of service via the panic. Fixed in 0.103.13 and 0.104.0-alpha.7.
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-2026-93599 has been found in rustls-webpki.
Risk of unauthorized operations or information disclosure. CVSS score: 7.5/10.
What to do: upgrade rustls-webpki to 0.103.13 or later.
If unsure, ask your IT team or search "rustls-webpki CVE-2026-93599" on the vendor's site.
CVE-2026-93599 (rustls-webpki) — CWE-191 / CVSS v3 7.5
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Patched: 0.103.13 — 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.
A vulnerability (CWE-191) exists in rustls-webpki.
Check the vendor advisory for the affected versions of rustls-webpki.
Severity: High (CVSS 7.5/10). Risk of unauthorized operations or information disclosure.
Update to 0.103.13.
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 'rustls-webpki' . 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
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1Identify exposure identify
grep -r 'rustls-webpki' . | 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
rustls-webpkiを grep し、稼働しているサービス・バージョンを把握する。 -
2Apply patch patch
Upgrade rustls-webpki to 0.103.13ステージング環境で 0.103.13 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。
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3Post-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。
References
- web github.com
- web vulncheck.com
- web nvd.nist.gov
- web github.com