rustls rustls-webpki up to 0.103.12/0.104.0-alpha.6 DER Parser src/der.rs bit_string_flags onlySomeReasons out-of-bounds

Summaryinfo

A vulnerability categorized as problematic has been discovered in rustls rustls-webpki up to 0.103.12/0.104.0-alpha.6. Impacted is the function bit_string_flags of the file src/der.rs of the component DER Parser. The manipulation of the argument onlySomeReasons results in out-of-bounds. This vulnerability was named CVE-2026-93599. The attack may be performed from remote. There is no available exploit. It is advisable to upgrade the affected component.

Detailsinfo

A vulnerability, which was classified as problematic, was found in rustls rustls-webpki up to 0.103.12/0.104.0-alpha.6. Affected is the function bit_string_flags of the file src/der.rs of the component DER Parser. The manipulation of the argument onlySomeReasons with an unknown input leads to a out-of-bounds vulnerability. CWE is classifying the issue as CWE-125. The product reads data past the end, or before the beginning, of the intended buffer. This is going to have an impact on availability. CVE summarizes:

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.

The advisory is available at github.com. This vulnerability is traded as CVE-2026-93599 since 09/18/2026. The exploitability is told to be easy. It is possible to launch the attack remotely. The exploitation doesn't require any form of authentication. Technical details are known, but there is no available exploit.

Upgrading to version 0.103.13 or 0.104.0-alpha.7 eliminates this vulnerability.

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Productinfo

Vendor

• rustls

Name

• rustls-webpki

Version

• 0.103.0
• 0.103.1
• 0.103.2
• 0.103.3
• 0.103.4
• 0.103.5
• 0.103.6
• 0.103.7
• 0.103.8
• 0.103.9
• 0.103.10
• 0.103.11
• 0.103.12
• 0.104.0-alpha.0
• 0.104.0-alpha.1
• 0.104.0-alpha.2
• 0.104.0-alpha.3
• 0.104.0-alpha.4
• 0.104.0-alpha.5
• 0.104.0-alpha.6

CPE 2.3info

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CPE 2.2info

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