CVE-2026-93599Public exploitNetwork attack vector

Denial of service via empty BIT STRING

Published Sep 18, 2026 · Updated Sep 18, 2026

Panic in rustls-webpki through 0.103.12 and 0.104.0-alpha releases before 0.104.0-alpha.7 allows remote attackers to crash apps via CRLs. The bit_string_flags() guard accepts an onlySomeReasons BIT STRING containing only a zero padding byte, then subtracts one from an empty data-slice length and indexes out of bounds. Reachability requires opt-in RevocationOptions and attacker-influenced CRL bytes; the default rustls configuration is unaffected, and the resulting panic interrupts the application.

CVSS severity8.7
High
EPSS probability0.35%
Next 30 days · Oct 19, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Panic in rustls-webpki through 0.103.12 and 0.104.0-alpha releases before 0.104.0-alpha.7 allows remote attackers to crash apps via CRLs. The bit_string_flags() guard accepts an onlySomeReasons BIT STRING containing only a zero padding byte, then subtracts one from an empty data-slice length and indexes out of bounds. Reachability requires opt-in RevocationOptions and attacker-influenced CRL bytes; the default rustls configuration is unaffected, and the resulting panic interrupts the application.

The record

CVE
CVE-2026-93599
Published
Sep 18, 2026
Updated
Sep 18, 2026
Vendor
Rustls
Product
rustls-webpki
Classifications
CWE-191, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Sep 18, 2026CVE publishedPublication date reported by the CVE source.
  2. Sep 18, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=0 <0.103.13
  2. Affected versionversion=0.104.0-alpha.1 <0.104.0-alpha.7

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Rustls · rustls-webpkiversion=0 <0.103.13; version=0.104.0-alpha.1 <0.104.0-alpha.7

Published CVSS scores

7.5GitHub Security AdvisoryCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
8.7VulnCheck CNACVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Activity data is delayed. The latest report is Sep 28, 2026.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 22, 2026Sep 28, 2026
Latest reporting daySep 28, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-191Integer Underflow (Wrap or Wraparound)
T1499.004Application or System Exploitation

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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