What is CVE-2026-97873?

CVE-2026-97873 is Legacy PBES1 and PKCS#12 PBE iteration count honoured unbounded in the raw JCA provider. The supplied enrichment data classifies it as Denial of Service mapped to CWE-770 CWE-770.

Which versions are affected?

Affected product and version evidence is listed in the product table above. Current public advisories should be checked for exact version scope before patch targeting is finalized.

Is there active exploitation?

Active exploitation is not confirmed from current sources for CVE-2026-97873. If exploitation is not confirmed from current sources, teams should document that status and continue monitoring KEV, vendor, and telemetry updates.

No. CVE-2026-97873 is not listed in CISA KEV in the supplied enrichment data. KEV status should be monitored because it can change after initial disclosure or after exploitation becomes publicly confirmed.

Is there a public exploit?

2 public PoC repositories reported; 0 marked weaponized in current dataset. Public exploit or PoC availability should raise triage priority, especially for exposed or business-critical systems.

How can defenders detect it?

Start with web/proxy/WAF logs, application logs, network IDS/IPS where available. Look for vulnerability-class behavior, product errors, suspicious authentication events, exploit probes, and abnormal process activity based only on evidence that applies to the affected product.

How should teams prioritize it?

Prioritize CVE-2026-97873 using CVSS 5.3, EPSS 0%, KEV status, public PoC status, and asset exposure. Internet-facing, privileged, or business-critical deployments should be handled first.

Are workarounds available?

The supplied mitigation guidance says to apply vendor patches and restrict external exposure until fixed. Fixed-version evidence is listed in the mitigation section above.

Which threat actors are linked publicly?

No public threat actor linkage is confirmed from current sources. Do not attribute exploitation to a threat actor unless the source evidence explicitly supports that linkage.

What should be done in the next 24 hours?

Identify exposed assets running affected vendor/product/version combinations. Prioritize based on EPSS, PoC availability, and external exposure. Search available logs for exploit probes, errors, authentication anomalies, or suspicious child processes matching the vulnerability class. Open remediation tickets with affected assets, owners, evidence status, and detection coverage so decisions are traceable.

mediumDenial of Servicepublic exploit

CVE-2026-97873

CVE-2026-97873 — Legacy PBES1 and PKCS#12 PBE iteration count honoured unbounded in the raw JCA provider

In Bouncy Castle for Java before 1.86, the raw JCA provider's legacy PBES1 (PKCS#5 scheme 1) and PKCS#12 PBE families ran their password-based key derivation with an iteration count taken from untrusted input without bounding it, so a small input could dictate an arbitrary amount of work before anything could be verified. The AlgorithmParameters implementations (PKCS12PBE and its object identifier aliases, and PBKDF1) accepted any count from an encoded PKCS12PBEParams or PBEParameter, narrowing a value beyond the int range with intValue(), and every Cipher, Mac and SecretKeyFactory in these families derived with whatever count it was given, including one decoded by another provider's AlgorithmParameters, as when javax.crypto.EncryptedPrivateKeyInfo.getKeySpec() decrypts a PKCS#12 PBE-protected private key with BC. Both the parameter parse and the derivations now reject a negative or over-limit count under the org.bouncycastle.pbe.max_iteration_count property (default 10,000,000) that already bounded PBKDF2 (CVE-2026-17508), and the parse rejects a count beyond the int range rather than narrowing it. This issue also affects Bouncy Castle for Java LTS before 2.73.13.

Published Oct 3, 2026Updated Oct 3, 2026Sources: NVD, Legion of the Bouncy Castle Inc. (CNA), GitHub, GitHub Security Advisory, SOCRadar CTI

Triage

Is it exploited, how likely is exploitation, what does it touch, and how severe do the scoring sources call it.

Exploitation

Exploit code

public exploit, none observed

EPSS

ahead of 0% of scored CVEs

Affects

Legion of the Bouncy Castle Inc.

2 products listed

CVSS base

5.3

medium

Remediation

The vendor's own words where we have them.

Upgrade BC-JAVA to a fixed release. Apply vendor patches per advisory and restrict external exposure of the affected component until patched.

First 24 hours

Ordered from the record's own fields — exposure first, because you cannot patch what you have not found.

Identify exposed assets running affected vendor/product/version combinations.
Prioritize based on EPSS, PoC availability, and external exposure.
Search available logs for exploit probes, errors, authentication anomalies, or suspicious child processes matching the vulnerability class.

Affected scope

Vendor, product and version as the advisories word them.

Vendor	Product	Versions	Status
Legion of the Bouncy Castle Inc.	BC-JAVA	0 to < 1.86	Vulnerable
Legion of the Bouncy Castle Inc.	BC-LTS-JAVA	2.73.0 to < 2.73.13	Vulnerable

Attack characteristics

The CVSS vector, decoded. It describes the attack, not your exposure to it.

Scope

Attack Complexity

Low

Attack Vector

Network

Privileges Req

None

User Interaction

Every base score collected

Sources score independently and disagree; each row says who scored it and under which version.

Score	Version	Severity	Expl.	Impact	Source
5.3	CVSS 4.0	medium	—	—	Legion of the Bouncy Castle Inc. (CNA)

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/U:Amber

What this weakness leads to

MITRE's own consequences and mitigations for the weakness class — the authority's wording, not guidance derived from the CVSS vector.

MITRE

CWE-770 · Allocation of Resources Without Limits or Throttling

DoS: Resource Consumption (CPU)
DoS: Resource Consumption (Memory)
DoS: Resource Consumption (Other)

Mitigation: Clearly specify the minimum and maximum expectations for capabilities, and dictate which behaviors are acceptable when resource allocation reaches limits.

Weakness & attack patterns

CWE-770

Attack patterns reported against this CVE. The ATT&CK techniques below are inferred from its weakness class.

CAPEC-528 · XML FloodCAPEC-230 · XML Nested PayloadsCAPEC-496 · ICMP FragmentationCAPEC-493 · SOAP Array BlowupCAPEC-487 · ICMP FloodCAPEC-147 · XML Ping of the DeathCAPEC-495 · UDP FragmentationCAPEC-486 · UDP FloodCAPEC-489 · SSL FloodCAPEC-469 · HTTP DoSCAPEC-231 · Oversized Serialized Data PayloadsCAPEC-494 · TCP Fragmentation

T1498.001Network Denial of Service: Direct Network Flood
T1499Endpoint Denial of Service
T1499.003Endpoint Denial of Service: Application Exhaustion Flood

Public exploit

Capability, not use: code existing is a different claim from anyone running it.

Repositories

Detection

Read off the CVSS vector and the weakness class. Starting points, not rules we have tested.

Prioritize edge telemetry for network-reachable BC-JAVA, BC-LTS-JAVA.
Monitor for scanner or exploit-pattern traffic after 2 public PoC repositories were reported.

web/proxy/WAF logsapplication logsnetwork IDS/IPS

Timeline

What happened to this CVE, newest first — with the readings a source repeats on a schedule counted underneath rather than listed.

2026
Added · CVSS 3.1 5.3 (AV:N)
Oct 3, 2026 · NVD
Initial · CVE published
Oct 3, 2026 · NVD
Added · GHSA-78x9-mjv2-rr3v published (medium)
Oct 3, 2026 · GitHub Security Advisory
CVE published by MITRE.
Oct 3, 2026 · SOCRadar CTI

References

4 on the record

github.com/bcgit/bc-java/commit/766a31026ac24ed3c6cad8662058ba450c338da1
Exploit, Third Party Advisory, NIST
github.com/bcgit/bc-java/wiki/CVE%E2%80%902026%E2%80%9097873
Exploit, Third Party Advisory, NIST
nvd.nist.gov/vuln/detail/CVE-2026-97873
NVD
github.com/advisories/GHSA-78x9-mjv2-rr3v
Exploit, Third Party Advisory

Elsewhere on this site

Legion of the Bouncy Castle Inc.every CVE for this vendor
Denial of Servicesame class
CWE-770other pages naming this weakness

Not in any source we poll

Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.

No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
No exploit packet captures, log samples, or incident case IDs supplied.

Answered from this record1

What should defenders know first?

CVE-2026-97873 is Legacy PBES1 and PKCS#12 PBE iteration count honoured unbounded in the raw JCA provider, a medium vulnerability affecting BC-JAVA, BC-LTS-JAVA from Legion of the Bouncy Castle Inc.. The current evidence does not list it in CISA KEV, and the exploit status is: Active exploitation is not confirmed from current sources for CVE-2026-97873. Public exploit evidence is: 2 public PoC repositories reported; 0 marked weaponized in current dataset. The affected-version evidence is listed in the key facts and affected products tables. Defenders should first verify whether exposed or business-critical assets run those versions, then apply vendor patches or mitigations, restrict reachable attack surface, and preserve logs for detection review. CVSS 5.3 describes technical severity, while EPSS 0% helps estimate near-term exploit likelihood; neither replaces asset context. Unknown fields should remain explicit in tickets, and threat actor, IOC, victimology, or payload claims should not be added unless a cited source supports them. Monitor CISA KEV, vendor advisories, NVD changes, public PoC repositories, and internal telemetry for update triggers.