Is CVE-2026-71884 exploited in the wild?

No. Junglewise Threat Intelligence has no report of CVE-2026-71884 being exploited in the wild.

How severe is CVE-2026-71884?

Informational severity, published 9 October 2026.

Which products and versions are affected?

Bouncy Castle Java LTS before 2.73.13.

Is there a fix for CVE-2026-71884?

Yes: fixed in Bouncy Castle Java LTS 2.73.13. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

How is CVE-2026-71884 attacked?

It is attacked over the network, in a software library.

Am I affected by CVE-2026-71884?

Check whether you run Bouncy Castle Java LTS at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

CVE-2026-71884: Bouncy Castle Java LTS CTR cipher counter overflow

CVE-2026-71884 · Severity: info · Published 2026-10-09

Bouncy Castle Java LTS contains a flaw in its native CTR (counter) mode encryption where the cipher does not properly validate input length against available counter space. When using a short initialization vector (IV), an attacker can cause the cipher to reuse the same keystream across different message segments, allowing encryption without a key to be broken. The vulnerability silently returns success without alerting the caller that encryption failed.

Vendors: Bouncy Castle.

Quick answers

Is CVE-2026-71884 exploited in the wild?: No. Junglewise Threat Intelligence has no report of CVE-2026-71884 being exploited in the wild.
How severe is CVE-2026-71884?: Informational severity, published 9 October 2026.
Which products and versions are affected?: Bouncy Castle Java LTS before 2.73.13.
Is there a fix for CVE-2026-71884?: Yes: fixed in Bouncy Castle Java LTS 2.73.13. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-71884 attacked?: It is attacked over the network, in a software library.
Am I affected by CVE-2026-71884?: Check whether you run Bouncy Castle Java LTS at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

How to fix

Fixed in: Bouncy Castle Java LTS 2.73.13

Technical details

The native one-shot CTR packet cipher in Bouncy Castle Java LTS fails to validate that the requested input length can fit within the counter space derived from the IV. In CTR mode, a 13-15 byte IV leaves only 1-3 bytes for the counter, exhausting the counter range (256 to 16M blocks) before the input is encrypted. When the counter wraps, the keystream repeats and the same plaintext blocks are encrypted under identical keystreams, allowing recovery without the key. The fix implements pre-flight validation of counter range before processing.

Affected products

Bouncy Castle Bouncy Castle Java LTS before 2.73.13

Timeline

2026-10-09: disclosed

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