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No exploitation reportedFix available

CVE-2026-63575

PKCS#12 key derivation loops about 2^32 times on a zero or negative iteration count

No exploitation reported by the sources we read.

  • Published2026-10-02
  • Fixed in2.7.0
  • WeaknessCWE-835

Am I affected?

With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.

Description

Loop with unreachable exit condition in the PKCS#12 key derivation (Pkcs12ParametersGenerator) in Legion of the Bouncy Castle Inc. bc-csharp before 2.7.0 allows an attacker who can supply a PKCS#12 (PFX) file, or a PKCS#8 encrypted private key that uses a PKCS#12 password-based encryption algorithm, to cause a denial of service through CPU exhaustion via an iteration count of zero or below, because the derivation loop ran until its counter equalled the count, so for such a count it wrapped through about 2^32 iterations before the MAC or the password could be checked. A 75-byte PFX file with a negative MacData iteration count kept Pkcs12Store.Load busy for many minutes.

Timeline

dates in UTC
  1. 2026-10-0208:17CVE publishedNVD

Observed activity

isMalicious corpus · updated 2026-10-28 15:37 UTC
Indicators tagged with this CVE, per day0 indicators over 7 days
Block these indicators
  • Firewall list (EDL, text): https://api.ismalicious.com/edl/cve/CVE-2026-63575?format=txt
  • CSV export: https://api.ismalicious.com/edl/cve/CVE-2026-63575?format=csv
  • TAXII collection of exploited CVEs
  • The EDL and CSV take an API key on the Pro plan.

Versions per branch

NVD
Bouncycastle bc-csharp
BranchAffectedFixed in
2.7< 2.7.02.7.0

as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.

Fix

  1. Update Bouncycastle bc-csharp to 2.7.0

Advisories and patches

Detection

Nuclei template
none so far
ProjectDiscovery
Exploit-DB
no entry
Exploit-DB
Proof-of-concept repositories
none listed
PoC-in-GitHub

Sources

  • CISA-ADPSSVC decisionnone2026-10-02
  • OpenCVESSVC decisionnone—
  • CNACVSS 4.07.1read 2026-10-28
  • NVDCVSS 3.17.5read 2026-10-28
  • CNAweakness (CWE)CWE-835read 2026-10-28
  • FIRST EPSSEPSS score0.2 %2026-10-26

Technical details

CVSS v3 Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
CVSS 4.0 vector
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/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
Published
2026-10-02
Last Modified
2026-10-28
NVD status
Analyzed

Frequently asked questions

What is CVE-2026-63575?

Loop with unreachable exit condition in the PKCS#12 key derivation (Pkcs12ParametersGenerator) in Legion of the Bouncy Castle Inc. bc-csharp before 2.7.0 allows an attacker who can supply a PKCS#12 (PFX) file, or a PKCS#8 encrypted private key that uses a PKCS#12 password-based encryption algorithm, to cause a denial of service through CPU exhaustion via an iteration count of zero or below, because the derivation loop ran until its counter equalled the count, so for such a count it wrapped through about 2^32 iterations before the MAC or the password could be checked. A 75-byte PFX file with a negative MacData iteration count kept Pkcs12Store.Load busy for many minutes.

Is CVE-2026-63575 actively exploited?

Active exploitation of CVE-2026-63575 has not been confirmed. Its EPSS score was 0.2% on 2026-10-26, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2026-63575?

CVE-2026-63575 has a CVSS v3 base score of 7.5 (HIGH severity), with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.

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