CVE-2026-93599

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.

CVSS v3 7.5 HIGH

7.5^/10

CVSS v3 : HIGH

Vector :

Exploitability : 3.9 / Impact : 3.6

Attack Vector NETWORK

Attack Complexity LOW

Privileges Required NONE

User Interaction NONE

Confidentiality Impact NONE

Integrity Impact NONE

Availability Impact HIGH

Scope UNCHANGED

References

Link	Resource
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
https://github.com/rustls/webpki/security/advisories/GHSA-82j2-j2ch-gfr8

Configurations

No configuration.

History

18 Sep 2026, 15:17

Type	Values Removed	Values Added
References	~~() https://github.com/rustls/webpki/security/advisories/GHSA-82j2-j2ch-gfr8 -~~	() https://github.com/rustls/webpki/security/advisories/GHSA-82j2-j2ch-gfr8 -

18 Sep 2026, 14:19

Type	Values Removed	Values Added
New CVE

Information

Published : 2026-09-18 14:19

Updated : 2026-09-22 20:25

NVD link : CVE-2026-93599

Mitre link : CVE-2026-93599

CVE.ORG link : CVE-2026-93599

JSON object : View

Products Affected

No product.

CWE

CWE-191

Integer Underflow (Wrap or Wraparound)

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