# CVE-2026-115946: XS::libbrotli versions before 1.2.1.0 for Perl bundle a brotli library with an out-of-bounds write in the decoder

Status: published. Published: 2026-10-31. Updated: 2026-11-06.

XS::libbrotli versions before 1.2.1.0 for Perl bundle a brotli library with an out-of-bounds write in the decoder.

Affected versions compile a bundled brotli into static archives that dependent XS modules link against at build time, rather than using the system library. The bundled copy, 1.0.7 or 1.1.0 across the range, carries the decoder out-of-bounds write described in CVE-2026-111497. Version 1.2.1.0 updates it to brotli 1.2.1.

XS::libbrotli has no Perl interface, so the decoder is reached through any dependent module that decompresses untrusted data with it. An attacker supplying a crafted brotli stream can corrupt decoder state, disclose memory, crash the process, or potentially execute arbitrary code. Upgrading the system brotli does not remediate this.

## Remediation

- fix: Upgrade to XS-libbrotli 1.2.1.0 or later and reinstall every XS module built against it. (source: CNA: CPANSec)

## Affected products and versions

-  /  (XS-libbrotli): ≥ 0; < 1.2.1.0 (affected, custom). Source: CNA: CPANSec

## Severity and prioritization

- CISA KEV: No listing in collected sources

- EPSS: 0.24% as of 2026-11-05; percentile 15.71%

- SSVC: exploitation none; automatable yes; technical impact total; source ADP: CISA-ADP

- Weaknesses: CWE-1395

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://www.cve.org/CVERecord?id=CVE-2026-111497 (CNA: CPANSec; vendor-advisory, related)

- https://github.com/google/brotli/releases/tag/v1.2.1 (CNA: CPANSec; release-notes)

- https://metacpan.org/release/SYBER/XS-libbrotli-1.2.1.0/changes (CNA: CPANSec; release-notes)

- https://github.com/google/brotli/releases/tag/v1.2.1 (9b29abf9-4ab0-4765-b253-1875cd9b441e)

- https://metacpan.org/release/SYBER/XS-libbrotli-1.2.1.0/changes (9b29abf9-4ab0-4765-b253-1875cd9b441e)

- https://www.cve.org/CVERecord?id=CVE-2026-111497 (9b29abf9-4ab0-4765-b253-1875cd9b441e)

## Provenance

- CNA: CPANSec: https://www.cve.org/CVERecord?id=CVE-2026-115946; retrieved 2026-11-06; source updated 2026-11-06

- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-115946; retrieved 2026-11-03; source updated 2026-11-02

- FIRST EPSS: https://api.first.org/data/v1/epss?cve=CVE-2026-115946; retrieved 2026-11-06; source updated Not reported

Revision: 512a452e903c951accd128155f0f8bd7202814dbdda607e95501d90ef0771b32

Canonical: https://y2.dev/cve/CVE-2026-115946

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