# CVE-2026-93599: rustls-webpki before 0.103.13 Panic via empty BIT STRING CVE-2026-93599 is fixed in 9 products on 1 platform, first by RHSA-2026:85848, released September 18, 2026. It is not reported as exploited. Patch Radar priority: High. - Web page: https://patchblox.com/security/cve/CVE-2026-93599 - Priority: High - CVSS: 7.5 (Important) - EPSS: 0.0035 - CISA KEV: not listed - Exploited (vendor report): no - Publicly disclosed: no - Published: Sep 18, 2026 - Weakness: Integer Underflow (Wrap or Wraparound) - Vendor advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-93599 ## Description 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. ## Where it's fixed | Platform | Product | Fixed in | Fix | Released | |---|---|---|---|---| | Linux | aws-nitro-enclaves-cli opensuse-leap 16.0 | 1.5.2~git0.1c496ed-160000.1.1 | [OPENSUSE-SU-2026:22175-1](https://patchblox.com/security/data/fix/linux/opensuse-su-2026-22175-1.md) | Nov 7, 2026 | | Linux | aws-nitro-enclaves-cli sles 15.6 | 1.5.2~git0.1c496ed-150600.10.18.1 | [SUSE-SU-2026:5066-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-5066-1.md) | Nov 7, 2026 | | Linux | aws-nitro-enclaves-cli sles 15.7 | 1.5.2~git0.1c496ed-150600.10.18.1 | [SUSE-SU-2026:5066-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-5066-1.md) | Nov 7, 2026 | | Linux | aws-nitro-enclaves-cli sles 16.0 | 1.5.2~git0.1c496ed-160000.1.1 | [SUSE-SU-2026:24467-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-24467-1.md) | Nov 7, 2026 | | Linux | goose RHEL 10 | 1.45.0-1.el10_2 | [RHSA-2026:80765](https://patchblox.com/security/data/fix/linux/rhsa-2026-80765.md) | Oct 13, 2026 | | Linux | goose RHEL 9 | 0:1.45.0-1.el9_8 | [RHSA-2026:80764](https://patchblox.com/security/data/fix/linux/rhsa-2026-80764.md) | Oct 12, 2026 | | Linux | rust-rustls-webpki Debian 14 | 0.103.13+ds-1 | [DEBIAN-CVE-2026-93599](https://patchblox.com/security/data/fix/linux/debian-cve-2026-93599.md) | Sep 19, 2026 | | Linux | rust-sequoia-sq RHEL 10 | 1.4.0.1-4.el10_2 | [RHSA-2026:85848](https://patchblox.com/security/data/fix/linux/rhsa-2026-85848.md) | Sep 18, 2026 | | Linux | rust-sequoia-sq rocky 10 | 0:1.4.0.1-4.el10_2 | [RLSA-2026:85848](https://patchblox.com/security/data/fix/linux/rlsa-2026-85848.md) | Nov 7, 2026 | | Linux | rustup opensuse-leap 16.0 | 1.29.1~0-160000.1.1 | [OPENSUSE-SU-2026:22016-1](https://patchblox.com/security/data/fix/linux/opensuse-su-2026-22016-1.md) | Oct 2, 2026 | | Linux | rustup sles 16.0 | 1.29.1~0-160000.1.1 | [SUSE-SU-2026:24014-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-24014-1.md) | Oct 2, 2026 | | Linux | sccache opensuse-leap 16.0 | 0.18.0~2-160000.1.1 | [OPENSUSE-SU-2026:21982-1](https://patchblox.com/security/data/fix/linux/opensuse-su-2026-21982-1.md) | Sep 30, 2026 | | Linux | sccache sles 16.0 | 0.18.0~2-160000.1.1 | [SUSE-SU-2026:23983-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-23983-1.md) | Sep 30, 2026 | | Linux | sequoia-sq almalinux 10 | 1.4.0.1-4.el10_2 | [ALSA-2026:85848](https://patchblox.com/security/data/fix/linux/alsa-2026-85848.md) | Nov 7, 2026 | | Linux | sequoia-sq ol 10 | 0:1.4.0.1-4.0.1.el10_2 | [ELSA-2026-85848](https://patchblox.com/security/data/fix/linux/elsa-2026-85848.md) | Nov 7, 2026 | | Linux | sequoia-sq opensuse-leap 16.0 | 1.5.0-bp160.1.1 | [OPENSUSE-RU-2026:22132-1](https://patchblox.com/security/data/fix/linux/opensuse-ru-2026-22132-1.md) | Nov 7, 2026 | | Linux | shadowsocks-libev opensuse-leap 16.0 | 3.3.6-bp160.3.1 | [OPENSUSE-SU-2026:22189-1](https://patchblox.com/security/data/fix/linux/opensuse-su-2026-22189-1.md) | Nov 7, 2026 | | Linux | shadowsocks-rust opensuse-leap 16.0 | 1.25.0-bp160.1.1 | [OPENSUSE-SU-2026:22189-1](https://patchblox.com/security/data/fix/linux/opensuse-su-2026-22189-1.md) | Nov 7, 2026 | --- Data as of 2026-11-10T01:44:33Z UTC. 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