---
cve: "CVE-2026-93599"
severity: "HIGH"
cvss: 8.7
epss: "0.4%"
vendor: "rustls"
kev: false
exploited: false
published: "2026-09-18 14:19:11"
tags: [cve, security, high]
source: tsecurity.de CVE-Dossier
exported: "2026-11-05T08:48:46+01:00"
---

# CVE-2026-93599

> 8.7 HIGH · 🧪 PoC

## Beschreibung

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.

## CNA-Record (Kanon, cvelistV5)

- CNA: **VulnCheck**
- State: PUBLISHED
- Stand: 2026-09-18 14:15:25
- CNA-CVSS: **8.7** (`CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N`)

## CISA-Anreicherung (vulnrichment/ADP)

- CISA-SSVC (Coordinator, v2.0.3):
  - Exploitation: **poc**
  - Automatable: **yes**
  - Technical Impact: **partial**

## CVSS-Vektor

```
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
```

| Metrik | Wert | Bewertung |
|---|---|---|
| AV Angriffsvektor | Netzwerk | bad |
| AC Komplexität | Gering | bad |
| PR Privilegien | Keine | bad |
| UI Interaktion | Keine | bad |

## Schwachstellen-Klasse

- **CWE-191** — Integer Underflow (Wrap or Wraparound)
  The product subtracts one value from another, such that the result is less than the minimum allowable integer value, which produces a value that is not equal to the correct result.

## Patch verfügbar (OSV)

- 2879b2ce7a476181ac3050f73fe0835f04728e86 (Commit)
- d3b9a6db1e3b7a81ca1e1e6136a303f4ab11b32d (Commit)

## BSI-Hinweise (deutsch)

- [Red Hat Enterprise Linux (goose, environment-modules, tornado): Mehrere Schwachstellen](https://wid.cert-bund.de/portal/wid/sicherheitshinweis/WID-SEC-W-2026-3883) — _BSI-Einstufung: hoch_
  Ein Angreifer kann mehrere Schwachstellen in Red Hat Enterprise Linux ausnutzen, um Sicherheitsmaßnahmen zu umgehen, vertrauliche Informationen offenzulegen, beliebigen Code auszuführen oder Denial-of-Service-Zustände herbeizuführen.

## Referenzen

- <https://github.com/rustls/webpki/security/advisories/GHSA-82j2-j2ch-gfr8>
- <https://www.vulncheck.com/advisories/rustls-webpki-before-0.103.13-panic-via-empty-bit-string>

---
_Exportiert aus dem [tsecurity.de CVE-Dossier](https://tsecurity.de/sicherheitsluecken/cve-2026-93599/) · Datenquellen: EUVD (ENISA), NVD, OSV, CISA KEV, FIRST EPSS, Exploit-DB, BSI WID (CSAF)_